Logo

Lathe - Cutting/Parting

 
 

 

 
 
Parting tool chatter (Sep 25, 2001) Cutter size (May 23, 2003)
Proper Cutoff Techniques (Dec 5, 2001) How to cut disk?  (Oct 18, 2003)
Cutting oil- newbie questions (Jun 28, 2002) Cutting HSS (Jan 20, 2004)
Proper cutoff tool usage (Dec 31, 2002) Cutting/coolant solutions? (Feb 27, 2004)
Cutting off (Apr 25, 2003) Cutting urethane (Jul 31, 2004)
Using cut-off tools (Apr 28, 2003) Same Speed Same Feed Different Cutters (Nov 10, 2004)
 
Parting tool chatter
I've tried to use my parting tool a number of times but every time it chatters, digs in and throws the belt off. This happens even when I feed at an extremely slow rate. I've sharpened the tool per the instructions in the "How To Run a Southbend Lathe" and have taken great care to make sure the alignment is correct. What could be the problem? Gary (1598)
Did you set the height correctly. It should be just a bit above the centerline of the part, but not too much. Say about a hair or so. The cutting force will pull the tool down a bit. If the tool bit is too high it won't be cutting on the edge. If to low it won't be cutting square to the edge. I don't know what type of tool holder you are using. If its a lantern type, look to see when you have it set up that the front angle of the tool has sufficient clearance. Also, keep the length of the tool as short as possible. You might put a bit of cutting fluid on it too. Tom (1599)
1) Extend the tool the bare minimum needed. 2) Make certain that the cutting edge elevation is exactly on center, or slightly above. 3) *Increase* the rate of feed. Orrin (1600)
I've had similar experiences. Assuming that you have done everything the other guys have suggested; 1. Run the lathe in back gear at the lowest speed possible 2. Make sure that the part is properly supported in the chuck or collet, and as close to the chuck or collet as possible. (Flex in the part is as bad as flex in the tool holder!) 3. Support the outboard end with a center. 4. Use a little cutting oil. 5. Brass will want a zero or some negative rake angle. (1602)
If all else fails, take 2 alternating, overlapping plunges to part. Take small amounts off each time. Some use back-mounted, upside-down parting tools. Reportedly this is more reliable. (1604)
Whenever I run into a particular problem I do a Google search of the rec.crafts.metalworking newsgroup under the name teenut. This problem comes up cyclicly and Robert often had something to observe on the subject. Here's one snippet of what Robert had to say, based on 50 years in the business: Re: Parting tool use and questions? Sun, 06 Aug 2000 12:33:17 GMT Robert Bastow teenut@N... Newsgroups: rec.crafts.metalworking Then raweich@m... wrote: Then Robert Bastow wrote: "Sound advice..to which I would add this: Most people treat the pre-ground HSS parting blades as a finished tool, ready for use. It is NOT! No more than a ground, square, HSS tool bit is a ready to use tool. Parting tools NEED side clearance. This must be ground into the blade before use. When re-sharpening has reduced the length of useable blade below the radius of the piece to be parted off. start again! Snap or grind off the short end and regrind side clearance on a new section...new blades are cheap enough to buy! Let's belay all this crap about whether the blade should be at, above or below center. ANY and EVERY lathe tool should be set at dead center height. PERIOD. If you get better results by not doing so. you are doing something WRONG and need to re-examine the geometry of your tool bit. Unless you are parting off SMALL diameters, and wish to reduce or eliminate the center "Pip", the nose of the tool should be ground SQUARE to the body. Any angle to the nose will, invariably, deflect the blade to one side, during deep cuts. resulting in binding, rough finish, non-flat surfaces or breakage. More importantly, an angled cutting edge produces a chip WIDER than the slot. how do you expect this to escape freely from the cut? Better, even than a square grind, is a slight radius, or as I use a broad "Vee" shape to the nose. This flows the chip in on itself, producing chips that are noticeably narrower than the cut and which clear the slot easily. If you want to add belt to suspenders, use a tiny mounted point to grind a shallow, radiused groove LENGTHWISE in the top face of the tool. Examine a carbide, inserted parting tool tip, to get an idea of the best geometry to achieve. Chatter is reduced by INCREASING feed! Power feed will give best results. Rigidity of the entire set up is next to Godliness! Lock all slides not in use. Normal cutting speeds are the rule. Reduce ONLY if your rigidity is suspect. Reduce overhang to a minimum. both in the tool setup and the workpiece. Avoid Lantern type tool posts and Armstrong tool holders like the plague. Especially the angled parting tool holders. the worst abomination ever foisted on unsuspecting machinists. If you can't afford a rigid tool post. MAKE one! Rear mounted toolposts have definite advantages. Deflection of the tool or workpiece tends to lift the cutting edge OUT of the cut, rather than forcing it deeper...this by dint of the geometry involved. Mounting the parting tool upside down, in the front tool post, and running in reverse, has the same effect. This same arrangement works wonders with broad form tools too. Part off as close to the chuck as possible. If a long overhang is unavoidable, or the parted off piece is relatively long. use GENTLE pressure from the tailstock to prevent whipping and chatter. Remove this just before final breakthrough or you may get a jam up. Judicious use of a fixed steady, a wedge of wood 'twixt toolpost and job, or, (dare I say it,) a well lubed hand, (NO GLOVES PLEASE!!) will also help to reduce chatter in these circumstances. Lubrication is a MUST except on free cutting brass and MAYBE good grades of grey iron. Drip feed or flood lubrication, matters not. Just bear in mind that a happy parting tool sounds like frying bacon. The instant it starts sounding grouchy add more lube. teenut (1612)
For many years parting off was the most difficult operation I had too do. Then I found a fantastic solution to this problem. Its called a goose neck spring parting tool holder. Mine for my 9" SB is a straight shank Armstrong No S-20. I used to creep up and back off to get a cut and Quite frequently resort to a hacksaw to cut the last 1/4". Now I powerfeed quickly all the way. Assuming you have a rigid setup the only other thing needed is a good cutting oil. I use an old tooth brush dipped in Rigid dark threading oil and held on the cut. The MSC new 2002 cat has Armstrong gooseneck parting tool holder for the 9" for $146. Unfortunately the 13" lathe size is $ 239, and 16" is $298. Because they work so well I have acquired several other spring tool holders mostly for 1/4 and 3/8" bits. Great for thread cutting. These even work well in shapers. A couple of others ones I have are home made. If you look at the cat pic you could machine one yourself. There may even be designs on the rec.crafts.metalworking newsgroup. Walt (1616)
Lots of great advice on parting. One other tip on parting that I got from Scott Logan: * If possible, part with power in-feed This will give you a smooth, fairly fast feed rate, rather than a jerky, hand feed rate. It really works better. You may wet your pants the first time you try it, but it really does work.  Bob (1619)
Proper Cutoff Techniques
Are there any rules of thumb or recommendations from the "old hands" for properly cutting off finished pieces? Is the technique different for pieces between centers as opposed to being in chuck or collet only? Should the diameter be reduced to zero with the part actually falling off or is the diameter reduced to a "safe" point and then hack-sawed off? Should there be some side-to-side "wiggle room" cuts or just a direct inward cut the width of the cutter? Just curious as to how folks "in-the-know" deal with cutting off situations. Jim (2323)
A few months back this was discussed. I will say my technique would vary as to part and weather it is a manual machine or CNC. Also, type of material and size of part comes into play. Ideally, I want to make one straight in cut using power feed. Peck feeding with a cutoff tool can create problems. With a CNC machine and possibly a manual machine, the size of the part can effect if I want to completely cut off the part or just have to snap it off. This works well if there is a hole through the part. Smaller parts (they tend to fly off some where) or parts that may get dinged are good candidates to just have the part held on to be snapped off. They may not land in the parts catcher in a CNC lathe. Basic recommendations: Look up Ron's post and follow it. Failing that : 1.The tool height should be on center or slightly above center of Diameter of part. This depends on the flexing of the machine and tool. You want the tool while cutting on center. The cutting will draw the tool down a bit when cutting. (see #2) 2.Keep tool length (tool blade , tool holder, etc) as short as possible to reduce flexing (a major problem) 3.Try to keep an even feed, try a slow feed with power feed. 4.Lub the cut with oil during the process. 5.Adjust speeds and feeds as needed and for the type of material. Tom (2324)
Here are a couple of pointers. First do NOT part off between centers. The work will bind and something in the chain will get damaged. You can part down until almost through, then finish with a hacksaw off the lathe. Use a stone and hone the cutting point of the parting blade. Get it sharp. Use lots of oil or lube of choice based on material. Align the cutoff blade carefully. If the sides start to rub, the blade and work heats up, and you start to bind. Use a good cutoff tool and blade. The $20 made in India tool I bought years ago never worked well for me. A good parting tool and blade cleared up most of the parting problems I had. Be sure the tip of the blade is square to the blade. If it is a skew point, it will try to cut a curve. Feed aggressively. Slow feeding makes heat. If the chips don't clear, retract and clear them off with a brush, then resume. Parting requires a rigid setup. Part as close to the jaws or steady rest as possible. A piece may be 2 inches diameter and only 8 inches long, but if you're parting 6 inches from the chuck you're going to see things start to wiggle. Use the least extension of the toolholder and blade as possible. Pay attention to where the compound is when parting. If the compound is extended, you have a lever. Try to have the compound set so that the thrust goes straight down to the cross slide, rather than having the far end of the compound slide waving in the breeze. Have your gibs set correctly. Loose gibs will cause you a world of frustration. I often snug the compound gib a bit before parting. Be sure to be on center or slightly above center. If you are below center the work will ride up on the blade and catch. If you are going to have a hole through the center anyway, drill/bore/ream/whatever the hole before parting. The less you have to bury the blade in the work the easier you life gets. As the diameter decreases, the more the work wants to catch or chatter. Stan (2327)
What's a "gib?" Bilal (2342)
Bilal, the gibs are the thin steel strips that are used to adjust the play in the sliding dovetails of the cross slide and compound. The exposed screw heads on the sides of these parts are gently snugged up to remove all looseness in movement. The screws bear on the gib strip, which in turn slides on the male dovetail. If these are too tight, motion is difficult. If too loose, the assembly can shake around a bit, resulting in chatter or varying depth and quality of cut. Stan (2343)
Cutting oil- newbie questions
Just wondering what you guys use for turning (heavy 10, HSS cutters, lantern toolpost) 1- gray iron 2- 2011 aluminum 3- mild steel 4- 4130 Chrome moly steel anything different for threading the above? Tom (4794)
I have been using a product called cool tool 2.The stuff is non toxic, as these things go, and the smoke from it doesn't bother my sinuses. Its supposed to be good for all metals. All the regular supply houses handle it. RC (4795)
Tom; Here goes: Cast Iron - cut dry 2011 Al - kerosene, tapmagic, cool tool, WD40. Kero is pretty darn cheap, works well, and isn't any more flammable than a lot of other lubes. I just mention this because sometimes people get nervous about using the same stuff that can be used in a heater :-) Mild Steel, Chrome moly - any cutting oil, I often use Mitee dark thread cutting lube thinned with a bit of kero. It's cheap and works pretty well. Quite often I just cut mild steel dry, at least for the majority of stock removal, occasionally giving a bit of lube if chips seems to be welding to the tip. And a few more: Brass - Dry Copper - milk/half and half/whipping cream I use 1/2 inch indexable tooling a lot. Cheap per tip and good for heavy fast cutting. Critical stuff often gets a finish pass with M2 or better ground to the correct tip geometry for the material and task at hand. Stan (4796)
Tom, I use Tri-COOL. It cost about $10 a quart. It is biodegradable and water soluble. I mix it in a spray bottle. I am using on an EMCO CNC machine. I think it does ok. I was wondering on your opinion on the 2011 Aluminum. Its suppose to be a free cutting type. Do you notice a difference between it and 6061? Enough to justify its cost? I am using an indexable inserts. Right now I am using a Rouse-Arno Aluminum type. Others have something similar. Tom (4798)
Proper cutoff tool usage
Last night I made up a mount for my unknown manufacturer milling attachment. Everything went as I expected except for the parting part of the process. What're the tricks to using a parting tool? I've got a 3/32 x 1/2 cobalt cut off blade. The angle was probably ground a little too sharp, but not ridiculously so. I tried it both with the lowest regular speed and the highest backgear'd speed, with similar results. Blade was on the centerline of the work. The problem was that the tool cut _very_ slowly and dug in and slipped the belt frequently (Belt tension was fine for regular turning). Didn't cut very smoothly either, and had a tendency to not cut straight in, but rather to dish the cut a bit. Altogether, it probably took me 15 minutes to a half hour to part off a 1.375" piece of steel. In 'how to run a lathe' they talk about flooding the area with oil, which I wasn't doing (yes, I frequently read directions after screwing something up... :-). Does that make a huge difference? I was also thinking that perhaps I didn't have the cut-off blade exactly perpendicular to the ways and that was causing the slightly dished cut and increasing friction, making stalling more likely? Also... Is there any reason not to use 1/16 x 1/2 blades? Seems like the less metal I was removing, the better it'd work. Mark (8385)
Mark, You **MUST** use plenty of cutting oil. Only cast iron, 360 alloy brass or some bronzes can be cut dry. A saturated acid brush is my applicator. Never let the cutting edge get dry. Hot rolled steel is the worst to part off followed by cold rolled. The tool tip has to be sharpened square across. Anything else will drive it to the side. The tip AND sides must be sharp for the full depth of cut, Anything less will invite dig ins and galling up at the sides. Top rake can be used for steel, but is not absolutely necessary. I don't use it. The chip should form as a tight roll, break and begin another, all the time making a sound sort of like bacon frying. Lowest back gear RPM is best. Any tendency to chatter means lower speed or faster feed. Don't baby it, but do force it to cut, watching for trouble. Did I say use plenty of oil? RichD (8388)
I'm not sure what this means. What's top rake? I'll definitely use oil next time. Lowest back gear RPM is _really_ slow, like 60 rpm or so (just guessing. Its on a 9" C). I really want to spin it that slowly? Mark (8390)
Cutting off gives me a fit also. I'm self taught and feel comfortable with all other procedures I use except cutting off. I get best results with slowest speed, but had mixed results with oil, ending up not using because of mess to clean up with not enough results. Almost ground a blade up trying different angles, rakes, etc. I'm a gingery fan so I use a lot of cast al and even that soft stuff gives me probs. Was glad to see the post on this problem as I hadn't thought to ask. I am looking forward to (hopefully) some answers. bill (8391)
Mark, YES, that slow. That is why they put back gear on a lathe :-) Top rake is the groove that is ground into the top at the front edge of a parting tool. Also, this contributes to chip breaking. Top rake is commonly used for all steel turning tools. If you use a lantern tool post and standard tool holders, the top rake is already set. RichD (8392)
Mark Although not as easy to try as Rich's good comments, another key element is tool mounting rigidity. When I had the original lantern toolpost with the traditional Armstrong cutoff tool holder, I used to dread cutting off in almost any material. I could sort of get by with the techniques suggested by Rich, but it still would sometimes be an adventure. I then got a QC tool holder (mine happens to be a FIMS, but Aloris or it's Chinese copies would do just as well). While the convenience of always having a tool at the proper cutting height, etc is nice, by far the most significant improvement from the QC holder in actually machining is in cutting off. I don't even think about it any more, I just grab the cutoff tool holder, put it in, and cut away (with lubricant on steel). I use the same cutting speed rules in FPM I would for ordinary turning of the material at hand. I still make sure the tool is sharp and straight across, but there is no "what's going to happen this time?" feeling when I cut off now. BTW, I have two cutoff tool holders, one with zero top rake for brass, etc, and the other with top rake (about 10 Deg. if I recollect) for steel. Mark, you asked what top rake is. It is the angle relative to horizontal formed by the top of the cutting tool in the direction perpendicular to the workpiece axis of rotation. So a tool with positive top rake tends to want to "dig in" to the workpiece, a good thing for steels (but bad for brass). Frank (8394)
Thanks for the definition! I do in fact have some top rake then, though I'm not sure how much. I forgot to mention when describing my setup that I have a Phase II quick change. I'm afraid that years ago I got spoiled when I was doing a little lathe work at my then employer's machine shop (I'm a computer geek in real life, but I was racing motorcycles at the time and couldn't afford to buy parts I could make). I used my recently acquired 9" once with the regular toolpost and quickly decided that $100 for a QC was cheap! Speaking of which. Anyone got any favorite sources for cheap phase II / Aloris AX size tool holders? I could use another couple regular turning holders. Mark (8395)
Enco sells them for about $25, I bought several the last time they had a free shipping special. When they arrived, they were Phase II, rather than generic. Phase II is just an American importer of Chinese stuff, that stamps their name on things, but I still like it better than no-name. C (8396)
Like Frank says, it's always an adventure when parting off, but you learn by mistake what works by doing it. Regarding lantern toolposts/holders, et al.: I only keep a set with a lathe for when the time comes to sell it. Otherwise I'd toss'em into the pasture! A good solid wedge or piston QC toolpost is the only way to fly. Rich (8398)
Cleeve Gives some fine points about the care and feeding of parting tools. Now while I have never used or ground a blade the way he shows, I use T15 "T" style cut-off blades straight in with no rake in the rear ot in the QC holder at the built in rake thus only needing to sharpen the front of the blade. For the rest of the article the methods shown and problems to be avoided are as valid today as when they were written http://groups.yahoo.com/group/mwhints/files/Hints%20%26%20Tips/  The file name is 2858-Parting.pdf  JWE (8401)
Quite a while ago I posted about how parting off was a nightmare. I'd been using a 1/8" carbide parting tool, the highest backgear speed, and no cutting oil on my 9"C. Well, on the advice of everyone here I parted something else off the other day at the slowest backgear speed, using a 1/16" HSS parting blade and plenty of cutting fluid. What a difference! It was super fast or anything, but no more stalling and much less swearing. Night and day better. Mark (9392)
Cutting off
Bill I'm not sure what you have in mind here, but if the idea is to cut off (from the front) by inverting the tool and running the lathe in reverse, be very careful. With any lathe using a threaded spindle (and I think all SB9s had threaded spindles), this arrangement makes the cutting force loosen the chuck on the spindle rather than tightening it. Even if you get away with it once or a few times it will bite you eventually. You only have to unscrew the chuck once while machining something in reverse to drive the message home very clearly. I expect you would be OK with the work held in a collet (assuming the collet holder is not one of the threaded variations). Frank (10458)
I fully understand what you are saying. I would probably be better off cutting the roundels with a hacksaw or my homemade chop saw. I would rather be safe than sorry rather than risk injury or worse. Thanks a lot for the safety tip. Bill C. (10465)
Bill Although cutting off has some inherent geometry advantages using an inverted tool at the rear (and the normal direction of rotation), cutting off can be done reasonably well from the front in a small lathe with a "regular" tool placement and rotation. You need a reasonably rigid tool holder (i.e. not a lantern holder), a properly sharpened cutoff tool, proper cutting oil, etc, but it can be made to work. I wouldn't give up quite yet. Frank (10479)
Frank. I think for now I am just going to keep cutting the pieces with a hacksaw. After I sell a couple of cannons I may order the T slotted S-4328 cross slide casting from Metal Lathe. Would be a nice addition for my lathe anyway. But like I said I will have to try and sell some cannons first to get the money for it. I don't want to take any chances and maybe break something on the lathe, I'm still paying on it. Bill C. (10480)
Frank can you describe a little about a properly sharpened cut off bit? Clint (10481)
Clint Let me start by saying I'm not a machinist, and most of what I know comes from trial and error, reading, etc. I would be happy if someone who does this for a living and/or had some formal training chimed in as well. Having said that, here is what I find works. 1. dead sharp- I use a hard Arkansas stone for final honing, but other methods may work equally well. Re-sharpen or hone frequently. I find that a not quite sharp cutting tool just make the finish less than perfect in plain turning, but has a lot bigger impact in cutting off (things jam, break, etc). 2. Cutting edge straight across (i.e. exactly parallel to the turning axis) viewed from the top. Otherwise the tool walks to the side in cutting off stock of any significant diameter. 3. About 3 degrees side clearance. This is the angle of the side of the tool to vertical (on each of the 2 sides) viewed from the end, giving clearance under the horizontal side edges. Commercial cutting tool bits come with this angle built in. The trick is to mount the cutting tool bit in the holder so each side still has this side relief (i.e. don't let the tool tilt side to the side due to the mounting). 4. I also grind in about 2 degrees of side relief on each side. This is the angle between the side of the tool and the work, viewed from the top. So the top of the bit is wider at the point it contacts the work than further back. Grinding this involves a compound angle, since you want to continue having 3 degrees of clearance (in the vertical dimension) while you grind in 2 degrees of relief angle viewed from the top. Clearly this relief needs to continue far enough back on the bit to clear the largest workpiece radius you plan to cut off. When you align the tool, make sure the cutting bit is exactly perpendicular to the turning axis (viewed from the top), so you actually get this clearance on both sides when cutting. 5 Front Clearance- This is the angle between the front edge of the tool (viewed from the side) and vertical. For steel you want this to be small, to give maximum support under the cutting interface. About 5 degrees is right. For softer materials this can be larger, perhaps 10 degrees. 6. Top rake- This is the angle between the top edge of the tool at the cutting point relative to horizontal, again viewed from the side. for most everything but brass you want perhaps 5 degrees here. For brass you want zero, or perhaps even a little bit negative. This says you really need at least 2 sharpened cutoff tools, one for brass and one for everything else (much like drill bits, etc). Note all of these angles are for the tool in its mount. If the tool bit holder holds the tool bit at some angle to the horizontal (as some lantern type tool holders do) you need to figure out separately what angles on the tool bit itself give you these angles when mounted. The angles which typically change with the mounting method are Front Clearance and Top Rake (the last two). Frank (10491)
Frank, This is one of the best (most understandable) write-ups that I have seen on this subject. THANK YOU from another that has always had parting problems. (10492)
I use a much higher rake, almost 45 degrees on a lot of parts, and have a holder that is about 30 degrees. I'd post in the photo's section, but it is currently full. If you want a pic, let me know. Dave (10493)
Dave, there is another site where photos can be posted, http://groups.yahoo.com/group/SouthBendLathePix/ Bill C. (10494)
Frank That is a real good explanation, ever thought about being a Teacher? Clint (10495)
Dave If you do not mind, I would like to see the pic, email me. Clint (10496)
Clint Not as a profession- I have been an engineer since I was about 2 (or so my parents tell me), and I still think of my job in the context of: "and they pay us too?". However I do find that, especially in the last 10 years ago or so, I enjoy teaching. Perhaps if Tyco dumps me, teaching might make an interesting change, especially if engineering jobs in NJ are still really scarce for engineers approaching 60. Frank (10497)
Frank is right on almost all factors in all circumstances when using the normal run of the mill cut-off blades. Now here is a little secret, they are not cheap but find some T-style blades made from wrought T-15 material, with these blades because of both the shape of the blade and the material it is made from you can get away with a 30 deg rake for your main relief and for the 1/16 inch or so just under the cutting edge 15 deg and the blade itself can sit flat in a normal tool holder. If using a 20 deg Aloris clone holder just do the relief at a straight 35 deg and cut. After I bough and used my first one of these blades back in 77 I have used nothing else and every time I try a standard one I remember why I switched, just like every time I drive a Ford I remember why I do not own one. JWE (10498)
Frank So far I have not had any trouble using a cut off tool, but I am always hearing people having trouble? Maybe I have just been lucky or beginners luck. I take that back, once I had a problem when I was playing around with sharpening, I had the tip narrower than the rest of the blade, then I had trouble with it binding as it advance. Only took one time not to do that any more! It seems to me that the less I try doing to the tool the better it does, it seems when I try to get fancy with it is when I get into trouble. Clint (10499)
Jim good advice taken, I sure have to take it now, since you are wise on the ford! Every once in a while, I have to get a Ford just to remind me why I drive Chevy about every 15 years or so. Clint (10500)
Clint. You're doing better than me. Tried the cut-off tool again today and had the same results. The work piece tried to climb the tool again. I reset the tool to center and tried it again, same thing happened. Reground the tip and gave it another try, fed the tool into the work piece as slow as possible and it jammed. I just don't have the knack for it or I'm doing something wrong. This is getting frustrating. Bill C. (10501)
Bill, are you using a tailstock center? I had the climbing problem even with a relatively short piece; tailstock center solved it. Amazed at how little length it took to mess things up without the center. Ran the center looser than normal so it didn't try to catch when it got real near cut through. (10502)
Bill How far away from the chuck are you trying to use the cut off tool? Rigid is the key word in part off work. There must be no deflection in the piece part, or chucking method. In hobby lathes this usually means that the part off tool must be used very close to the chuck or holding collet. This is especially true if the part being cut off is flimsy. Rich (10503)
I will try to answer the last three post without posting three separate messages.1;I just have the regular tool post that came with the lathe and can't afford one of the Aloris type tool holders.2;I am cutting only about .50 from the chuck jaws. and 3;haven't tried using the tailstock center when cutting off. Also I don't like the idea of trying to cut off material with a hacksaw while the lathe is running. So what am I doing wrong? Bill C. (10505)
Bill: I honestly don't believe that 9's and light 10's are very rigid machines. That's why knurling and cut off operations are so touchy. Lantern toolpost itself is not very rigid. that's why the toll post block performs better. Not necessary but it really makes you life much easier. Look in the files section or on metalwebnews for home project toolposts. Other things that come to mind- no matter how sharp your tool is it has to EXACTLY ABSOLUTELY perpendicular. Use a known parallel to set the tool against the face of the chuck. I use a 1-2-3 block against the chuck and another hss bit blank to bear against the blade. I also try and use the compound to try and bind it all together. That might be more difficult with lantern style toolpost but certainly possible. Keep your blade and tool holder stick out as short as possible. Deflection at the tip is a function of the distance cubed. Also, what is the diam of the material you are turning? at most, try to keep a 3:1 ratio of unsupported length to diam. beyond that, use a steady or tailstock to help out. Tool must be on center and the angle of blade dead flat. At least the way I grind and use: I use side tapered cut off bits and only grind the front to 5-7 degrees and then hone with a stone. lube: set up a drip oiler if you can, or a mister. Its hard to apply lube and advance the cutter. Consistent even feed is critical. I can not describe it, I go by feel and watch the chips curl. Once you master it, it will stay with you. dennis (10507)
Dennis. I plan on making another type tool holder as soon as I can afford to get the right kind of material to make it from. In the meantime I will try some of the other methods suggested and see what kind of results occur. I appreciate everyone's input and all the suggestions put forth. I really love this little lathe and love using it. It's probably one of the nicest things I have ever owned and I wouldn't want anything to break on it due to my ignorance. Bill C. (10508)
Bill It kind of sounds like something is flexing or giving a little, are you close to the chuck? any play in the tool holder? Cutter maybe slanted downward? Just sounds like some giving/flexing of some sort? Clint (10509)
Since you now have a furnace, you can cast the material needed for a cam/piston type QC toolpost, out of aluminum. Clint(10510)
Dave, I would like a picture. (10512)
I use a QC tool post and the standard cutoff holder that came with it. I part stainless, cold and hot rolled steel along with lots and lots of aluminum. over in the group, http://groups.yahoo.com/group/SouthBendLathePix/ I created a folder called 'cut-off tools" with 2 pictures. picture one is a blade that has a high rake, and the relief helps in cutting off as the chips in aluminum roll tighter and as many know chip control is often 90% of the problem with a good work. the second is a cutoff tool holder I purchased from a used too place and uses a huge blade for my 9" - 1/8" wide compared to the skinny blades of the AXA QC holder. my carbide tipped cutoff blade if straight, no relief other than the angle from the holder itself. I also have another blade that I leave straight, but have both ends ground. One end cuts of with angle towards the chuck when I'm cutting off scrap, and the other end with the point towards the tailstock for when I'm cutting of parts and leaving stock. I have a blade that is flat, do not use that exclusively. I use the one that matched the work. I keep an Arkansas stone (very hard) an grind the bits for a shaper edge, then stone the bits. top, front, both side, then hit the corners. When I hit the corners, I stone the front laying the stone on the lower relief and then the cutting edge and hone the cutting edge, then keeping the stone in that angle, rotate it 45 deg and take any grinding burrs off the corner, then rotate it again to the side so I am stoning the side flat. it gives the corner a little radius and takes off the burrs. use your 10x magnifier to inspect the edge of the cutter to make sure it is sharp. in the case of my high relief, I have a flat on the top of the cutting edge, not a knife point. It is stoned in, and probably only about 10 thou. If you don't have a drip oiler, consider a small can hanging higher than the part, with a tube. A clamp on the tube to crimp it to regulate flow and a magnetic clamp with arm to hold it in position. If you scour old junk yards, old old old refrigerators used 1/8 dia copper tubing. you can cut this off with wire cutters and use that as a very skinny straw for oiling. Pen parts also offer neat tubes and your friends will flip if they see you using a Gold Cross pen for your lube! Dave (10519)
Hi quality tool material does go a long way. If you saw my pic, I use a Tantung blade. at $50.00 it is NOT cheap, but for one blade for years, and no problems and the bragging rights. Dave (10524)
Dave if you ever see any Vasco Supream 3/32 or 1/8 x 1/2 T-style bits lying around anywhere grab some for me will you. JWE (10528)
I'm not going into the cutter shape and angles that's been covered pretty good. And its been said to make sure your centered this is critical. There was one post I saw on speed's I'd like to restate that most new chip makers run it to slow for parting of ( my opinion ) and feed to slow. I am working on a crankshaft for a little engin e. It's disk is 3/8" the shaft is 1/16" one piece. Now I did do this on my little 7x a lot less ridged that my SB9, cut off tool in front, side front relief, no bake rake, speed about 500 rpms to start, feed rate I don't know how to state it for sure but it took less than a min. to cut it off on the 3/8" ,but no a constant rate faster on the start slowing towards the center, and increasing spindle speed some as you approach center, cutting fluid was ATF. Just a side thought on cutting off I've been a wood turner for a long time and I think a good way to get an understanding of speeds and forces on using a parting off tool might be to get a cheap parting tool for wood form some one, chuck up some 1" wood dowel in the lathe and make a bunch of checkers. The Wood Dragon (10529)
Using cut-off tools
As a professional tool maker, one thing is the rocker type tool posts aren't very rigid, I just bought my 9" South bend about a week ago and have not cut on it yet and haven't run one of these little lathes in more than 20 years, but one thing that I see a lot of inexperienced operators do is to run the part to slow when they cut it off, I just cut a 2 1/2" diameter part off with an Aloris tool post at work yesterday and a 1/8" parting tool, I cut this part off at 355 rpm, most of the guys I see do this, do it at about 100 rpm which is way to slow, the material I cut off was also a piece of S-7 tool steel. The more rigid you can make your set-up the better, I also don't use oil to lubricate my tools, I use water soluble oil which is a mixture of about 50 parts water to 1 part oil. No decent tool maker uses oil any more haven't for 20-30 years, water soluble is much cheaper, no where near as messy and works generally better on cutting tools with the exception of taps and reamers. If you have a pan under your Lathe just use a fish tank pump to supply coolant to the tip of the tool, just remember to clean the lathe when done using for the day. (10511)
There are a lot of us home shop guys who have their machines on wooden benches and more than a few that have there shop carpeted. I am currently working on adding flood cooling to my band saw and then to my lathe, then the drill/mill. But, as the time honored tradition, spot lube is the way most of us go. I know a lot of guys (lots more than I would have thought) that use lard. The only thing I pay real attention to is tapping and using tapping fluid. for lathe work, I use what oil is handy, and if it smokes, the bit is too dull and/or the part spinning too fast. water-soluble oils are designed to not only add lubrication, but also cool the part. cold parts and cold tool make finishes better, edges last longer and parts more repeatable and metals are not work hardened. way too many benefits not to use them in any production shop. and since lathe work is confined to a relatively constant work envelope, it is very easy to add coolant. compare that to milling machines that need the same benefits, but have a much larger work envelope. I don' know any shops that use flood cooling on a knee mill, granted I am not familiar will more than a half dozen shops, but it seems that only fully enclosed milling centers have flood cooling. The benefits of flood cooling are extensive, and if one wanted to add that, the drain pan and chuck guard are about the only things needed. but water-soluble oils do rot and stink unless they are changed, and in home environments where tools are left unused for weeks or months, that means waste. also water on metal surfaces is bad. the oils will prevent rusting when the coolant is flowing as the oils attach to the metal, but after many hours of non use. and that means a thorough wipe down, followed by a drying, followed by an oiling after each project. assuming that after your project, you are not using the machine for a few days. (weeks...) I can't comment on the length of time water has been used, but I started in a production shop in the mid 70's, and it was on every production lathe, but not on every lathe. we had the pumps, the coolant, the drain pans, but just didn't need it on every lathe. so, I would argue that 'any decent toolmaker' would more correctly fit any 'professional shop' with the addition of 'when needed' as there are lots of retired guys making very high quality parts who chose not to use flood cooling for one reason or another and many shops who chose not to use it for one reason or another. Dave (10518)
Dave, not all water soluble rot and start smelling or need replacing and there are additives you can put into them to keep the smell down like cinnamon oil. When I speak of cooling with water soluble I don't mean flooding it like a machining center does, put you a gallon milk jug or coffee can above the machine and use an 1/8" hose with a small magnetic base to hold a brass tube and let it trickle on the tool, be it an end mill or a cut off tool or whatever, you can use this trick on a mill or a lathe. When I made my drip pan for my lathe to sit on I had a small lip bent on the tray and put a PVC fitting on the bottom with a plug in it so I can drain the tray into the jug and keep reusing the water soluble or store it in the jug till I use it later. Oil is ok for spot use but I never liked using it because it is messy and takes one hand to use it and I would never run it in a drip can on a tool because of the mess and sulfur oil stains the metal on the machine a dark color. Also a large chunk of knee mills made since the mid 70's have a coolant pump built into the base of the machine with a flood nozzle and drains in the table plummed to drain back into the base. (10525)
Dave Allow me to add that water soluble should only be used in light duty situations where the machine is running at minimum load. We have tried soluble on every machine in the shop and have gone back to oil on everything but some of the centerless grinders where the stock removal is not to heavy and finish quality is nit that important. Everywhere else in the shop tool life is from 10 to 30 times longer with high sulfur cutting oils and we are able to run faster cycle times as well. Good old fashioned brown high sulfur oil is the best tooling coolant there is when you are doing heavy metal removal. JWE (10526)
I agree 100% that any lube is better than not lube and that cooling is better than lube alone the messiness of water based solutions is a problem with come guys with wood benches and not drip pans. I found that mixing the coolant with water for a cut-off saw yields a nice white milky fluid, but once thru the pump and it seems to let the oils separate and then they float to the top. it is well worth the effort, but not everybody will gain a large benefit. Dave (10532)
Cutter size
Is there any advantage to using a 1/2 cutter rather than a 1/4 cutter on a South Bend 9" Lathe? Both seem to do the job but the 1/2" take forever to grind on my (not large) grinder. Larry (11413)
Well since were talking about a HSS cutter it will be more ridged, absorb more heat and take longer to burn up, also has more shock resistance in interrupted cuts. A 1/2" tool is a bit big for a 9" machine but that being said I have more 1/2" cutters then any other size and use them the most. Kerry (11415)
I've been using 1/4 on my 12 Atlas because that's what came with it. Now that I have to buy some more for the SB I thought I'd check before I'd stock up. Maybe I'll try 3/8 if it doesn't make a lot of difference. The 1/2 really do take a while to grind. Larry (11425)
5 to 10% cobalt Thanks for the tip. I never tried carbide because I have no way to sharpen them. I tend to take many light cuts anyway. In the past I was somewhat over protective of the cast gears in my Atlas. The Atlas always served we well but I saw the SB and fell in love and no more change gears. Now if I can just learn how to use it. Larry (11453)
I buy 5/16" new and keep my eye out for used 1/2" already ground in useful shapes. I'll second the cobalt. Ed (11456)
I have no problem grinding my own tool bits and I prefer 1/4" HSS for my 9" South Bend. I do not have equipment to grind carbide and I really do not need carbide as most of my work is small and mild steel or aluminum. My experience with carbide was production work, heavy cuts and lots of horsepower, not what I do at home with my South Bend. When I switched from rocker type tooling to an Aloris tool post and holders, which work much better with insert type tooling, I purchased the Arthur R. Warner Co. 1/4" tool holder's which use their T-15 HSS Throwaway inserts. The insert's look just like carbide but they are HSS. They are 1/4" I.C. (same as carbide) triangle shape i.e. three cutting surfaces, 1/32" or 1/64" radius, and reasonably priced. at $4.00 ea., purchased in quantities of ten, They can be touched up on your grinder if you are so inclined. They are available in 3/8" also but the inserts are $7.00 ea. I believe. I love my system now, very speedy when producing small parts, especially multiples that necessitate a lot of tool changing. Warner advertises in Home Shop Machinist, phone 724-539-9229. I highly recommend. If I need special shapes, etc. I grind my own and sometimes revert to my old rocker holders which I kept of course. Neil (11476)
How to cut disk?
Is it possible to use my 9" SB to cut 1/16 and 1/8 aluminum plate into 4-6 inch disk? If so how do suggest I hold to stock. Need 6. Also, how would I go about knurling the edge? Larry (14481)
You can glue them to a faceplate one at a time on top of a slightly smaller disc or you can use a center in the tailstock with a cone shaped mandrel a little smaller than the disc and put enough pressure against the piece to be cut to hold it. The glue and mandrel together will work best of all. The backing disc can be held to the faceplate with flat head screws or held in a chuck. You can remove the disc with heat from a torch when you are done. The piece between the work and faceplate should be slightly smaller than the finished work and thick enough to give clearance to the knurling tool. JP (14485)
JP, This seems to be the only avenue and I did consider it, but I didn't think that glue would hold up to this kind of pressure. I'll let you know how it works out when I start the project, maybe next week. Larry (14487)
Someone else here did the face of some discs and held them with glue. Doing the edge and knurling them will probably require the added pressure from the tailstock. JP (14503)
They do make a knurler that is hand held. It has knurling wheel on both sides. The pressure is into the part, rather than side pressure. I have used one before. They work good. Tom (14530)
Cutting HSS
I just bought a bimetal blade for my bandsaw. I need to cut some HSS cutter blanks for cutters in my boring bar. They are 1/8" but I would also like to cut some other blanks that range up to 1/2".Do you think the blade can do it without destroying itself? I also have a Dremel cutoff wheel. Would that be better? Tom (16679)
Use the abrasive wheels, the tool blanks are harder than your bi- metal blade. (16680)
Tom, The 1/8 blanks can be scored with an abrasive disk in the Dremel, then snapped off by holding one end in a vise and the free end in an adjustable wrench and snapping off. Some folks wrap the bit in heavy paper, put it in a vise with the score just above the jaws, and hit it with a hammer. Overkill for 1/8 inch blanks, but about right for 1/4 inch ones. I grind most of the way through on a bench grinder (around 1/4 to half way through on each side) rather than use up dremel abrasive disks, the little bonded disks aren't cheap when you snap 10 of them to get through a single cut and the reinforced disks wear fairly fast for this sort of use. Once you get past 1/4 inch sizes you will need the reinforced rather than bonded abrasive disks if you decide to use the Dremel. The little benchtop cutoff saws use this style of disk, but not all Dremel dealers stock them. Auto parts places also have them for use in air powered cutoff tools, just the thing for some exhaust work when conditions or nearby things prevent the use of a torch. Bimetal blades are good for plenty of things, but this isn't one of them, sorry... If you try, odds are you'll strip a few teeth at first, then the rest will follow shortly thereafter. One of the downsides of bimetal is that once you strip a few teeth the rest don't last long. You'll be out the blade and still have uncut tool blanks to deal with. When I have to cut 1/2 inch blanks and want minimal waste I use a larger cutoff saw with a 14 inch disk rather than grinding in on each face with the bench grinder. Usually burns the steel at the cut zone, so you either use just the uncut end or grind off around 1/16 inch at the cut end to get back to good steel. If your can cut the blanks with a file/hacksaw/bandsaw, the blanks must be some low end unknownium/importium blend of steel, not real HSS. A quick check for the "Can I cut this stuff on my bandsaw" question is to try an old file on the material. If it cuts easily go ahead and slice it up. If the file snags and scratches but cuts a bit with heavy force it's probably too hard. If the file just skips over the surface it's too hard to cut with a bandsaw. You can also test with a hacksaw, if that won't cut the material neither will the bandsaw. Stan (16681)
Tom: CAN'T Cut toolbits with bandsaw. You can use Dremel Tool with Cut-Off Wheel. Ron (16682)
Cutting/coolant solutions?
I did see where someone mentioned WD-40 for aluminum and found it works very good. Someone mentioned using a citrus cleaner, does that work well and on what types of metals? I have a gallon jug somewhere that I bought where you mix it with water. I tried it and stopped using it because of the possibility of rust. The recirculating pumps seen in shop photos are simply not practical for the home shop. At least for me anyways. What works for you? Joe (18702)
I always use Kerosene or in a pinch diesel fuel for machining aluminum. Small cans of cutting and tapping fluids are available at all industrial suppliers. Lubricants don't always work well for machining as sometimes they defeat the purpose by their very nature. I found cutting fluids work much better than say WD40 for lathe and bandsaw work on metal. Paul (18705)
I use kerosene for cutting aluminum. Kept in a small lab wash bottle, you can squirt into bores or just dribble a bit on the piece being turned. At $1.60 a gallon or so, it's cheap. Downside is that it smells pretty bad. For steel I use heavy thread cutting oil, applied with an acid (flux) brush. A weighted bottle with a 1/2 inch hole in the lid holds the oil. If it tips over, very little oil runs out. The hole holds the acid brush, while leaving little room for swarf to enter. Tapping is usually done with TapMagic. Stan (18707)
Plain old plumbers dark threading oil from the hardware store works for me. It is too heavy for tapping small holes and buy the small cans of special fluids for that job. John (18713)
For "heavy" turning on my 9 inch I use the same plumbers' cutting oil, but have it diluted about 50% with kerosene. Somebody at GE recommended that to me 35 years ago. Better yet, in my opinion, is to use carbide cutting tools -- then most if not all things can be turned dry. No mess, no stink up the shop OR the house. For small diameter drilling and turning I use Winbro Tap-Free. It seems to be some sort of chlorinated solvent, possibly containing beeswax. Steve (18731)
Cutting urethane
I have 3" dia. urethane wheel on a 1" plastic hub (think rollerblade wheel). How can I cut a half inch off the dia.? Dremel in tool post? Right now I don't have a spare to experiment on. I may have to buy another to practice on. Larry (20283)
If you want to cut the 3" wheel down to 2 1/2" use straight forward MS- 101. If the piece is pressed onto a shaft or has a hub as you say, just use a sharp tool with a very acute rake. Ron (20284)
The machinery handbook calls for 200 to 300 ft/min speed and zero top and side rake and 10 to 20 deg clearance angles. HSS tool. It is a pain to deal with. It needs a lot of power and a sharp tool. Low clearance and it binds, incorrect rake and the tool moves the part like a corkscrew. JP (20293)
JP and others, I did the job with a Dremel (toolpost) grinder. Worked great. Larry (20294)
Freeze it hard, before machining it. Gary (20295)
Same Speed Same Feed Different Cutters
I'm trying out some carbide cutter bits. Some Grizzly TCMT 32.51 uncoated 60 degree inserts and some TIN Coated TPG 322's. I laid the 322's to a 7/8" stainless bar at .005 feed and .005 depth and turned a baby butt smooth finish. Then came the uncoated import insert at the same rates and it felt like 2 days of rough beard growth. I'm sure it could be smoothed up, but it's amazing the difference in cutter finish quality. Has anyone out there come up with a good source for coated inserts? (21885)
Its easy to forget that the turned surface finish is effectively replicates the surface finish of the cutting edge. So if the edge is not really smooth and continuous neither will the surface be. Sticky materials like aluminum really show this up as slight imperfections in the tool edge act as an open invitation to material build up on the tip. Naturally any dings, scratches or imperfections in the edge will not be quite as sharp as the rest of the tip and build-up is always more likely on a blunt tool. Blunt tools, as we all know, tear rather than cut the metal which is bad for finish. There is no hard dividing line between tearing and cutting, its just that the sharper the tool is the less the tearing and the better the surface finish until its good enough. The way the metal comes off also affects things. If you can get it peeling off nicely like an apple skin the finish is much better. Doesn't have to be a continuous chip, it just has to peel. Carbide tips are inherently grainy and therefore a teensy bit rough. The better the make the smoother they are but you can never get as good an edge as you can with HSS or high carbon steel (best). In general carbide tips need to be operated with a decent cut and feed relying on the peeling effect to give a good finish. The coating process makes the surface finish much better so the carbide behaves more like HSS and gives you a better finish especially when used, as we do, at feeds and speeds below the optimum. Clive (21893)
 
     
 

Index       Home Page