Lathe - Leadscrew/Feedscrew



Leadscrew (Jan 12, 2002) Installing leadscrew with taper attachment (Jun 23, 2003)
Lead screw 'extension' (Jan 30, 2002) Lead Screw Question (Jan 29, 2004)
9A leadscrew support (Apr 28, 2002) Leadscrew thread form? (May 12, 2004)
Leadscrew re-installation (May 30, 2002) Lead screw binding (May 31, 2004)
Lead screw key way (Aug 15, 2002) Leadscrew size and pitch (Jun 10, 2004)
Lead Screw Reverser (Dec 3, 2002) Leadscrew Bracket Bolt (Nov 21, 2004)
Leadscrew TPI (Dec 21, 2002) Lead screw bearings (Nov 22, 2004)
Leadscrew autom. crossfeed SB9 A (Jan 5, 2003) 9" C Leadscrew (Nov 29, 2004)
Heavy 10 lead screw size? (May 1, 2003) New feedscrews (Dec 12, 2004)
405Y Lead Screw (Jun 22, 2003) Making Low Backlash Feedscrews (Dec 25, 2004)
I got my threading dial finished except for the markings. Dunno whether I'll order a set of number stamps or use a fine-point permanent marker. after installing it I notice my leadscrew has about .040 TIR in the middle. Is this enough to be serious? I didn't notice it until I installed the threading dial and was eyeballing the wormgear engagement. And if it does warrant replacing the leadscrew, can I convert my "C" to an "A" or are the bed's different? (2685)
Why don't you just straighten it? I've seen everything from crankshafts to guns straightened with nothing more than the tool you have right in front of you - the lathe itself! Make a thin aluminum sleeve to protect the threads when you chuck it in the lathe. Apply some light pressure at the point of greatest runout with the compound and a well oiled crossfeed screw while you hold it between the chuck and a dead center. Spin it again while watching the dial indicator and keep repeating until you have it dead on. It won't take much pressure at all to move it .040". This assumes the runout is caused by a true bow that extends from one end to the other. If it's an "S" or other odd shape you'll have to straighten it a small amount at a time starting at the first bent section. My Hardinge had its crossfeed screw bent a total of .065" when the trucking company dumped it on its face, and because it has different cross-sections as you move down the screw, each one of the cross sections had bent a different amount. That took a lot of gentle tapping with a 5 pound brass hammer starting at the first bent section, but it ended up .0003" TIR in the end. All it takes is patience! Mike (2686)
Lead screw 'extension'
The previous owner of my Model C 9" SB, an auto electrician - butchered inside the ways with a - wait for it - angle grinder - so he could swing a larger armature. I have since bought a 3'6" bed for a HERCUS here in Oz which is almost perfect fit - but the HERCUS is 6" longer than the SB. So options are: (1) I extend the lead screw (several possible options); (2) I move the RH bearing and restrict the movement down the ways; or (3) I get a LONGER lead screw. As the HERCUS bed came with the ratchet tooth (terminology ??) for driving the apron fixed underneath - and the right length - I am tempted to add 6" of travel to the lead screw somehow. I rang HERCUS - they have stopped making them and said it would cost over $600 for a new one. They suggested I buy another used lathe and wreck it for parts (tempting). However it occurred to me someone out there MIGHT just have a longer leadscrew lying around in their shed. (2994)
Look on eBay if nobody answers here. Lots of stuff but you need to check all the time. I got a perfect replacement single lever type QC gearbox for my old 10" South Bend, net cost $87 to my door! B.G. (2995)
Interesting since I emailed Hercus from here and they told me I couldn't use their lever-lock tailstock on my South Bend due to the bedways being different. What's different? Those leadscrews aren't hard to find in the US. (3015)
9A leadscrew support
I'm looking for a leadscrew support for my 9A. Does anyone on the list have an extra that they'd be willing to part with cheaply or in trade for a copy of a good shop plans CD? Dave (4132)
Dave, Are you looking for the support that goes on the tailstock end of your south bend? Gerald (4133)
Gerald, Yup, that's the rascal. Mine was broken when the machine was pulled off it's table in the robbery. Busted the support and bent the leadscrew. Had another leadscrew but wasn't so lucky with the support. Dave (4134)
Dave, If your not able to find a tailstock end lead screw support I've got something that can be made to work. I converted my 9" model C (change gears) to a gearbox machine by adding a used quick change gear box. The cast iron leadscrew support at the headstock end is almost identical to the support at the tailstock end except: It has a 3/4" bore (with a keyway) rather than the 1/2" bore on the tailstock end. necessitating a sleeve being made. And, it has a 2" dia. boss on the left end that would have to be machined off. After machining off it would be the same length as the tailstock support. The good news is that the two mounting holes are in the identical location as those on the tailstock end support and the locating height is the same. I'm sure it could be made to work. I would be glad to exchange it for your shop plans CD. I'm not set up to take a digital photo for you but I have a friend who could. If you don't find exactly what you need and you would like a photo let me know and I'll see what I can do. Neil (4135)
Dave, I have an extra leadscrew support from an "9A" and I'll be glad to send it to you. I think you're supposed to use molten babbit get it aligned? This one still has the babbitt bearing from the lathe it came off of. Please let me know if you still need it and I'll be glade send it to you tomorrow. Tex (4136)
Tex, I do still need one and greatly appreciate the offer. Dave (4137)
If you have any trouble locating babbitt to redo that support, I found a big stash at a local scrap yard and bought some sticks. Would be happy to send a stick, enough to do the support. Rick K. (4142)
Fred, If I can ever get a way for a while, I get in touch and stop by. It actually would be a great to visit some of the folks here on the SB list and see their shops. O well, may be someday. Tex (4146)
Rick, I don't know whether Dave needs any babbit or not but I have a tip for making babbit bearings. The retired shop teacher, Chuck Hughes, at our local high school helped me install a taper attachment on my South Bend A9. When we got ready to do the babbitting he told me to get some peanut oil to use as flux. He poured to peanut oil in the bracket where the babbit was going and on top of the molten babbit in our ladle. It really helped the babbit flow and kept it from oxidizing. He says that he learned it from old timers when he was just starting out. He, also says, they tried other oils but the peanut oil was the best. I hope this will help someone. Tex (4150)
Rick, I thought I had a piece but haven't been able to find it. If you could spare some I'd appreciate it. Dave (4155)
Wouldn't have offered if I couldn't have spared it :-) It will go out tomorrow. How do you plan to establish proper alignment for the pouring? Rick (4156)
Rick, I'm gonna cheat and ask Mert. Dave (4157)
Leadscrew re-installation
Have you already called South Bend and checked their site? (4359)
Multiple times. I've posted this problem several times in the past. The lathe I have has had the ways ground so the serial number is gone, I have nothing to call SB with. The lathe has to be dated by some other method. (4360)
David: all the components that are matched (i.e. the cross slide, tail stock compound etc.) have code # stamped into them. Are any of these # still visible? Ralph at SB might be able to help if you have some of those #'s and an aprox date. Do you have the original motor? you might be able to date it and get some idea of the age from it. how are you making out getting the face plate off the spindle? Pete (4361)
Dave You said your lathe bed had been reground and you couldn't tell the SN to have sb now Le Blonde trace it for you. I am not sure about this one but working on guns for the past 30 yrs missing SN 's in steel is not the end of the trace so to speak. Can you find someone that can re lift the number for you. I am not sure of the process but I do have faith that some metal url S out there in the sight should be able to help you. I think that they use acid or something but they can get it back cause of the molecular effect on the metal of stamping it in the first place. It ant ever gonna be gone just not visible . Then you could even restamp it so it would be a perm. record again. Jim PS on light steel of guns for numbers and damascus patterning we bring it back with heating and then applying muratic acid to the steel. Makes a little mess at the area but nothing that cant be cleaned up. Good ventilation is a must.! (4371)
Lead screw key way
If I have a key way slot cut on a mod C leadscrew Is that all I need to do to run a cross feed Carriage and apron? And all I would have to cut the key way would be just the distance that the carriage travels? Clint (5772)
That's right Clint. I bought a Taig lathe headstock and mounted it on my cross slide. I set it up with an end mill and collet. I chucked the lead screw in the lathe with a home made 2 x 4 "steady rest". I drilled a hole in the upright 2 x 4 for a setscrew to keep the lead screw from turning while I rechucked it for the 3 passes it took to do the whole length of the screw. If you want to add your QC gearbox, you need to cut off about 6" from the headstock end of the screw, remove and replace the cuff, cut new threads and a keyway for the drive gear. Careful attention to clearances will reduce the amount of leadscrew backlash you end up with when you are done. Glen (5774)
Glen I am thinking of running the Power cross feed on the C using the Change gears instead of using the quick change. So it looks as though all I would need is a key slot for the apron/carriage. This is on one SB that I am rebuilding. The other mod C I have I plan on converting entirely to an A so I figure that I will just try and purchase a Mod A lead screw. I would attempt to convert a lead screw but my machinists skills are null and void right now, and I would like to get practice on something else before I attempt that Clint (5776)
Lead Screw Reverser
Is it possible to change the lead screw reverser on an early model 9" A to the later style with the plunger knob. so you don't have to loosen and tighten it every time you change directions? If so is it really an advantage? Randy (7719)
I did it. You have to make a plate for the plunger to hit. The holes have to be done very carefully because they determine the mesh of the gears. I could send you a drawing. Before I made the change, I frequently made cuts in the direction the lathe was currently on and not always the direction that was best! Now I change direction in a second, so I do not worry about the change - Bill (7727)
Leadscrew TPI
Does any one know the TPI on a SB 9" leadscrew off hand? Clint (8182)
Clint. It's 8 TPI going by my thread gage. Bill (8183)
Leadscrew autom. crossfeed SB9 A
I posted a question to Anthony. That I needed the crossfeed leadscrew off my SB9 model A with a Nut. because on my lathe the used the wrong one The one for model c ?. Or they make one but the gear isn't there!. So Know I have the Apron with the gears and it don't fit. (thanks To Glen) Because the gear in the apron reaches the crossfeed leadscrew. I wrote to Anthony that is maybe possible to make a gear at the leadscrew, If I know the DP and the number off teeth. He wrote back asked me to calculate, because I have the other gear And asked me to post here So I try it Don't Use this before its confirmed!! Determining or calculate DP off a gear formula = number off teeth +2 divided by OuterDiam in Inches Example I have a gear 45 teeth Outer Diam 59.7mm =2,35 inch Number off teeth + 2 = 45+2=47 47teeths / 2,35 = 20 DP --------------------- The gear on the leadscrew off the crossfeed diam 16.4mm /25.408mm =0,64 inch 20dp x0,64 inch od=12,9 teeth + 2 so the number of teeth =10,9 must be 11 Only the wy its 10,9 instead off 12 I really don't know Measured the crossfeed leadscrew 3 times Also with a micrometer 16.41 mm Maybe the bushing here isn't original hope someone can tell me grtz Bert (8508)
Machinery's Handbook, 25th Edition, page 1922. My "A" is 12 teeth, .678 OD which means 20.64DP [for full-depth teeth]. For stub-profile teeth, add 1.6, not 2: 13.6/.678=20.05 13.6/.680=20.0000000000 [I guess .002 wear on the OD over the years] On my "C" leadscrew the OD is .610. For 11 teeth, stub tooth profile, 12.6/20=.630 So you could cut an 11-tooth on the leadscrew you have. Your feeds would be 12/11 of what the gearbox data plate says [9% more]. To change to the "A" leadscrew you would maybe have to bore the saddle casting to .680 if the hole is smaller. I have an extra 9A carriage and leadscrew one person on this list says he maybe wants, but if he doesn't take it, you can have it. Lurch (8524)
Bad mistake I make--the "A" carriage is gone, it was the "C" carriage I was thinking of, same as you have now. Sorry about that. I am going to PKE [local used-lathe dealer] this week, if he has an extra leadscrew I will get it. (8526)
Lurchix the cross feed leadscrew fits in a bushing that's the one I must bore and not the saddle casting if the leadscrew is bigger no problem over the mistake If you want no mistakes you must sit still all day and nothing but that is a bigger mistake about the gear calculating thanks for correcting me. Bert(8530)
There is no bushing on mine. Is the OD of your bushing .680? ka9egw (8535)
Nice to know in my saddle is busch with threat on the outside a thinner part of the crossfeed lead screw fits in that I made a mistake the .64 thick part off the leadscrew is only in the saddle. Bert (8540)
Heavy 10 lead screw size?
Does anyone know the thread size of the Heavy 10 lead screw - diameter and TPI? Looking for parts for my 9" Junior. Bob (10677)
Bob 8 TPI, .750" diameter. This is a measurement on a 1957, but to my knowledge they were all the same. Frank (10685)
405Y Lead Screw
I borrowed an expensive digital camera and took a picture of the lead screw on my 405Y. It seems to be ACME and not square cut. I reduced the picture from 1.5 Mb to 26Kb partly by cropping and partly by reading into Paint and Re-saving it. I have placed the picture on  the soubend Yahoo group. It is labeled 405Y Lead Screw. This may not be definitive but at least two of us have ACME. I find it very difficult to see the difference between the ACME and the Square Cut since the screw is very shaded from the light. It is easier to try it with various number drills. It tales a smaller drill to get to the bottom of the thread than the top. Jim B. (12192)
Jim, I think most 405Ys are actually Acme, which is good news to anybody needing a replacement. Bill (12195)
Installing leadscrew with taper attachment
I am in process of installing a new crossfeed screw and nut in my SB heavy 10 and when comparing the bearings and washers I noticed some differences as compared to the SB drawings. My lathe has 3 of the machined washers and 2 thrust bearings. The drawing shows 2 of the machined washers with a thrust bearing running directly on the Cross feed shoulder. I also have a thin slotted cover for the thrust bearings and washers. This is not on the SB drawings. I assembled with washer, bearing, washer, bearing with the cover and noted that the bearing assemble is in the open when butting up to the taper attachment. I expected a recess in the taper tube to house the bearings. There is a recess on the other end of the tube. I have been using this lathe for over 20 yrs this way. Do I have it put together right? (12219)
There were two, different bearing set-ups. The newer machines (circa 1950+) used 2 sets of washer-bearing-washer. Install one set; slip into housing, then install other set on the outside with the two nuts. The spring-cover is a dust cover that goes over the last, outside set of bearings. You will know if correct by amount of threaded shaft extending out of housing. I do not know the arrangement for the older set-up. Others will. Joe (12222)
That's right. When I ordered a new thrust bearing it came as a thrust race and two washer set. The drawing Form 987 A in the SouthBend manual is not completely clear and it could easily be inferred that the bearing is a thrust race only. I assumed so having a surplus of washers and apparently missing thrust race at the back end of mine so getting a complete assembly was a surprise. Stripping down for installation revealed that the previous owner had assembled two bearing races at the inner end and put all the washers at the other leaving some endplay! The spring cover dooby goes on the inner end to keep the swarf out, on mine the bearing at the back is normally pretty much sunk into the bed bracket casting keeping it well protected. It only comes out for air during taper turning. If all is well there is just enough thread for the two nuts and the collar PT866R2sits about half on the plain shaft and half on thread. Clive (12223)
There were two, different bearing set-ups. The newer machines (circa 1950+) used 2 sets of washer-bearing-washer. Install one set; slip into housing, then install other set on the outside with the two nuts. The spring-cover is a dust cover that goes over the last, outside set of bearings. You will know if correct by amount of threaded shaft extending out of housing. I do not know the arrangement for the older set-up. Others will. Thanks, I have the setup you described. I was told my lathe is a 55 model but haven t verified yet. The service manual I have doesn't show it this way but it makes sense. This also means that my taper attachment was assembled incorrectly. I need to remove the shaft and reverse to have the housing recess towards the front of the lathe. I have used it incorrectly assembled for over 20 years. Joe (12224)
Clive, this means I won t have to go into the taper attachment to reverse the housing. Since the leadscrew is new I plan to face the end of the screw to eliminate play as per a SB page copy I found I had saved from prior group info. I've only been using the lathe with it incorrectly assembled for 20 + years. I bought it locally from a bench rest shooter gunsmith who had rebuilt it. Surprised he missed the assembly error. Joe (12225)
Lead Screw Question
I own an older 9" SB with a badly worn lead screw. I also have a second lead screw but it is shorter than the one on the lathe. Question: Am I crazy in thinking I can cut the worn lead screw off at the point where there is no threads and replace the old section with a section from the newer lead screw. It seems to me that I could make a collar to join the two lead screw pieces together. Similar to joining two pieces of plumbing. (16922)
You are not crazy, it has been done. There is a write-up of someone doing this to a cross slide screw I think in the files section. not sure if you are describing grafting it at the gearbox end or a the pilot bearing end, but I think that doing it to the gearbox end would work better. you could always try trading it with another list member. You'd be surprised how many parts we all have lying about. dennis (16926)
The section of the screw near the tailstock is seldom (almost never) used. Someone in the group, (Dr. Robert Harms?? I think, could be very wrong) just added an extension. A sleeve to fit over the end of the shorter one with a shoulder to fit into the rear bearing. This is a much simpler approach. Jim B. (16933)
Yup. That's what I did when I converted a 4 foot C to a 3.5 foot A. Worked fine (16934)
Leadscrew thread form?
What is the lead screw thread form on the 9" lathes. I appears to be modified us square. Any one know ? Tom (19003)
My computer hiccupped while I was typing my response. The lead screw is an acme thread, at 8 threads per inch. Ed (19005)
It's ACME, Tom; 8TPI 14.5 deg. thread angle. Rob. 19016)
IF you need new acme, apparently MSC has some and nuts also already done. I am sure other sources exist, but this is provided just to give you an IDEA of the availability. http://www.mscdirect.com/IWCatSectionView.process Enter the search term 'acme' in the box and click on components then threaded 'rod' or 'nuts and it will eventually get you to a pricelist etc. I am NOT responsible for your purchasing, nor recommending/associated with MSC in any way. Do so at your own risk. It is an acme thread, at 8 threads per inch. (19065)
Be very careful buying leadscrew from the import suppliers. We bought some from one of them and it was actually stamped, not machined. You could see a line running the length of the entire rod where the dies came together as they formed the thread. This didn't affect our product but I don't think I would use it on precise machinery. Paul (19072)
Lead screw binding
I have a strange problem with my 9" south bend. I am converting it from a model C to an A, all of the parts that I have look nearly new but when I put it all together the lead screw seems to bind. I have had it all apart several times, including the apron and the gear box and it all look perfect. By binding I mean the drive gear on the left side of the gear box is fairly hard to turn. The only thing that seems to free it up is if I put 1 .010 feeler blade between each end of the apron and the saddle, lowering the apron. I know this is not correct to have to shim the apron but I am out of ideas. This lathe is in good shape, no noticeable bed wear. Bill (19391)
I often find shims under the apron. Or you may have to shim the quick change box and the leadscrew support at the tailstock end, I see that more often. (19392)
Is it possible that the bed has been re-ground, lowering the saddle and thus, the apron? (19394)
Actually, lowering the saddle and apron would seem to "fix" the binding, not cause it. (19395)
Unless I'm still confused about this, shimming the gearbox would appear to make the binding worse. No? (19396)
Sometimes the carriage has to be shimmed to match perfect center to the output shaft on the gearbox. I have a 10" that came with shims under the gear rack in the middle so that the gear wouldn't lose contact with the rack where the bed was severely worn. I think you need to find dead center on that output shaft and check the end bearing and the hole center for the leadscrew. I am not an expert by any means but check it and get back to us. Paul (19398)
Bill, put the .010 shims in and if everything else works the way it should don't worry about it. Check slack in cross slide with out shims, check it with shims. If you have power cross feed. That is the only thing the shims will effect. Check your gear box mounting for dirt or shims. DM (19400)
I found the problem after much measuring, leveling, dial indicating and head scratching, the apron needed a .010"shim on each side. While removing the saddle to make a pattern for the shim I turned the saddle over and found one of the nice new felt way wipers I got from LeBlond was folded up under the front edge of the saddle. I have been working on this lathe for over a year and have not really run it much, when I got the power apron I removed the saddle to check the cross feed gear mesh, the felt must have folded then. Bill (19413)
Bill; It might be useful for you to know that I have heard that when South Bend regrinds a bed, they normally install shims between the gearbox/bed and the tailstock screw support/bed to lower the leadscrew an amount equal to the amount removed from the bed. I have found shims under the outboard leadscrew brackets on my own 9" South Bend. I made the same conversion you are doing on my old model C. It has turned out to be a very worthwhile modification and I have found it to be worth the effort. If you have a good bed, why not? Now it has all the bells and whistles my Heavy 10 has, with the exception of the taper attachment. Perk (19418)
Leadscrew size and pitch
I can't remember the lead screw size and pitch for a SB 9 inch. I'm pretty sure it is right hand, ACME, 8 tpi. But is it 5/8 inch or 7/8? (19586)
It's 5/8 Jim B (19587)
BTW, The early 9's (Model 405) were LH Threads. Jim B. (19590)
Yes it is 8 pitch and (see previous post) if its a later model it is RH. Jim B. (19593)
Anyone quote me the dimensions for a heavy 10? a 9 Jr? Dave (19594)
Just checked a lead screw from a SB "C" dia. 3/4" (19595)
Yes it is 3/4. But not 7/8 (19596)
My Model 82 (like a JR, but with QC feeds) has a 3/4-8 RH thread. (1927 vintage). Dave (19598)
 10L or Heavy 10 is 3/4 - 8. JP (19599)
Leadscrew Bracket Bolt
3 weeks to remove one bolt. I was 99% complete in tearing down my 9C. One bolt remained, one of the leadscrew bracket bolts. That SOB was not going to come loose. Screwdrivers - no good. Heat and cooling - no good. Impact hammer and sledgehammer (!) - no good. The latter finally broke the bit this morning. I've battling this beast for three weeks and brute force just wasn't doing the job. I finally broke down and did the method of last resort - used my brain. I went to the hardware store to buy a bolt removal tool. In my depraved, ah, I mean deprived youth we used what was basically a reverse threaded tap that kep the conical shape all the way to the top. The Ace hardware did not have those. What they had was something similar but with a spiral cut into it and one that was just a tapered square. Talking to the very young assistant he told me that the best to use was the square one. He insisted that it was the best. I walked out of the store with mumbling under my breath something between "it better work" and "these kids nowadays". Picking up the 4' bed and putting it on the mill was a lot easier than I thought it would be. The HSS bits I had handy went into the bolt like butter and the bolt removal tool worked exactly like the kid said. Darn! Now I have to feel bad about thinking bad things about him. Walking into the house and giving my primal victory scream did not go over too well. So I sulked over here and wrote out the events. Now I'm off to clean a few inches of grime off of the bed. Gene (22152)
Way to go Gene! Hold your head up high g quiet. Oh yes, give that sales kid an attaboy next time you see him. Finding one that actually knows his/her stuff is very rare. Tom (22153)
Gene, The square screw extractors have a better bite than the reverse spiral ones. The material and heat treatment is important so use brand name extractors. The vibration from drilling the hole and the added flexibility after the hole may have helped loosen things up as well. The next time you order from McMaster get a can of 'Break Free CLP' It is the best weasel wizz I have ever used. It might have saved the drilling, etc. I never looked for it at MSC. I get it at the local gun shop. JP (22154)
I have a set of this style extractors. Only ones I have had any luck with. After drilling the hole you can use a ball pein hammer and tap it into the hole, it will twist around on its own.. Then a socket and ratchet to remove it and the bolt. Notice there is a much wider range of sizes then the typical spiral sets (that very rarely work) http://buy1.snapon.com/catalog/pro_det.asp?tool=allitem_ID=10522group_ID=1262store=snapon-storedir=catalog Unless the head of the bolt is totally destroyed, I have always been able to get stubborn lathe bolts out with the impact hammer trick. Although I do go through a lot of those bits. Luckily snap-on replaces those for free. Jeff (22156)
Lead screw bearings
I have a 1970 10L that has a little more play in the lead screw bearings than I really like. Took the QC down and cleaned out about 5 pounds of powdered brass and old grease (it was used to true brass glue rollers) to get to the bearings, but the bearings are showing some wear than I think cleaning and fresh grease will cure. Has anyone replaced the inner and outer bearings or had luck finding replacements? Is it worth using sealed bearings if they are available? BTY, bringing the QC box and cleaning it in the kitchen sink was not such a good idea. It is harder getting the little black grease spots off of the counter than cleaning it on the bench in the garage. But hot water and Castrol Super Clean sure made the box smoother. Mike (22200)
9" C Leadscrew
The army manual does not have a drawing of the model C leadscrew assembly. When I disassembled my system lateral movement was controlled by the headstock leadscrew bracket with the gear pulling on one side and the shoulder of the leadscrew on the other. There were no washers acting as a bearing. Is this correct? Gene (22345)
I have a very early C (1934 - Model 405) That the way it is. Jim B. (22346)
That s also the way it is on my 1946 Model B 9 . Neal (22354)
New feedscrews
I have to say I'm surprised with CNC coming to the home shop that no one has made replacement cross slide and compound feedscrews. Mine are quite worn, but the lathe is still useable. I'm afraid to ask what one of the things costs from LeBlond. It seems like a straight forward part to make but I have not tried to make one. Has anyone tried to make one? I've heard the acme taps are quite expensive to make the nut. I've thought of used, but how good a condition are the used ones vs. price for a new? Anyone replaced theirs? Alex (22881)
Alex I made cross feed nut on my SBL using vertical mill att. screw for check (it's same), previous doing special tool for threading. It was easy task. (22882)
Excellent! You're saying you made the tool to thread the hole? I guess just put it in the chuck and thread away? This will help with the wear problem, but only half the solution without a new screw to match. (22883)
I called LeBlonde, (this was right after they picked up S.B. parts), they wanted $52 for the nut, and $800 for the screw. I bought the nut and took the old screw to my buddy Harold. He made a new screw and it works every bit as good as an $800 factory made screw. Chris. (22886)
Alex, Not sure what size lathe you are working on, but if you can find a piece of ACME threaded rod the same dia and pitch, you can cut your old screw and pin in a new piece of threaded rod. This fix (on I believe a 13" SBL) used to be in the files section, I haven't checked, but might be worth taking a look. BK (22887)
Alex; I believe Miller Machine Fabrication sells new screws and nuts for around $200. (22889)
Made that same repair by pinning a new bought piece of Acme Threaded Rod on my 13". Works great. Got a tap from work and made a new nut also. Probably not as tight as a factory SB set-up but 100% better than what it was. Ron (22888)
Check with Plaza Machinery, Joe has ACME rod for the SB lathes. Just attach it to your existing shaft. I used a press fit and Loctite. The price was quite reasonable. He may also have a replacement nut. (22890)
Do you have any contact information for them? Alex (22891)
I've thought about attaching a new acme rod to it but wasn't sure if it would be lined up that well. If other have had success I'll give it a try. I actually have a spare crossfeed screw that is REALLY worn so I could experiment with that one. Thanks Check with Plaza Machinery, Joe has ACME rod for the SB lathes. Just attach it to your existing shaft. I used a press fit and Loctite. The price was quite reasonable. He may also have a replacement nut. (22892)
Actually I'm doing this to my 9". I have a 13"SB also, but it is in pretty good condition. The feedscrew has a bit of wear but nothing that needs to be replaced. Nothing like using one lathe to make parts for the other one!!! Made that same repair by pinning a new bought piece of Acme Threaded Rod on my 13". Works great. Got a tap from work and made a new nut also. Probably not as tight as a factory SB set-up but 100% better than what it was. Ron (22893)
BTW my leadscrew is pretty shot also. I've thought of threaded rod for a replacement. I've seen Enco sells, McMaster probably does too. Which leads me to new half nuts....aw nuts this gets expensive. But I got time. My 9" is more than twice my age so I know it's not going anywhere. (22894)
Make sure the screw is machined and not formed. Machined is cut from a blank, formed is made with a die while the metal is hot. The formed screw has a seam in it that makes it much less precise. Most of what Enco and the others sell is formed. Paul(22895)
I have used "rolled thread" Acme rod. This is roll formed and I haven't seen a seam on it (unless I misunderstand your reference). It comes in 1/2" x 10 tpi. Acme. The lead error is advertised as less than .001" per inch. This is usually good enough for cross feed screws and tail stock quill feed screws. Unfortunately, I haven't found a source of this type of Acme rod in 7/16" x 10 tpi. (single lead). Webb (22896)
The Enco screws are Keystone seconds. Not true leadscrews, but ACME threaded rod. ACME has some different varieties, but are not really listed like one would hope. If you look at your $3.00 Chinese vise ACME screw, you will see that you could do a better job on your lathe. Very poor thread quality. In my discussions with Keystone, they said the best quality is steel. that Stainless never gets as smooth a surface finish. Keystone does sell leadscrews as do McMaster, but make sure you buy leadscrews and not ACME threaded rod. As for the nuts, Google Moglice. This is the good stuff. First, you replace your leadscrew. Pretty easy as all you need to do is make a sleeve over the existing one near the headstock and then cut our your old one and then for the new one, turn the end for the bearing at the tailstock. With a new leadscrew, you take your crappy (worse is better in this case) half nuts and do the Moglice thing. This will be better (and faster) than a new set of half nuts. Dave (22897)
Is this for the cross slide on a 9" south bend I have one feed that I can trade. David (22898)
Haven't seen a seam on it (unless I misunderstand your reference). It comes in 1/2" x 10 tpi. Acme. The lead error is advertised as less than .001" per inch. This is usually good enough for cross feed screws and tail stock quill feed screws. Unfortunately, I haven't found a source of this type of Acme rod in 7/16" x 10 tpi. (single lead). Try Keystone. http://www.keystonethreaded.com/acme.htm or Techno-ISel http://www.techno-isel.com/tic/Quote/Default.asp?Page=Acme.htm They make rolled screws, but the difference is in the quality. if you look at a poorly rolled screw, you will see the minor diameter with a very poor finish, cups and edges and such. not a babies ass smooth finish like you would hope. Ground screws will be the best and the most accurate and also have a very high price tag. Keystone starts at 1/4" and makes all the normal thread pitches. BUT (you know that had to be coming) They have a minimum order. Most likely, you can spread the cost out among others in the group that want to do the same. If I replace the cross slide screw in my 9", I will also extend the dial and put on larger dials. Also, I am not sure that the the Keystone factory price is not high compared to distributors. Dave (22899)
Worth looking around for a small shop that makes "urgent" repair stuff for factory production line machinery and so on. These days they usually have CNC stuff for gears, screws etc. and are set-up for single or very short run jobs. One firm did a cross feed screw made for a friends Churchill Cub lathe for 50 and. a set of metric conversion change wheels to suit my Heavy 10 were under 150. Needs to be a small shop and cash job though. (22902)
Miller Machine and Fabrication is listed on the list of Links at the group site. Their address is www.millermachineandfabrication.com They are located in Carrollton, IL, phone 217-942-9296. (22937)
Same as the feedscrew, there used to be an article in the files section about fixing your half-nuts on 9" SBL ( I suppose the technique would be the same for all sizes, just different dimensions). I have not tried it out as my 9" had really good nuts on it. Have heard of some other members trying it and having good luck. BK (22942)
Making Low Backlash Feedscrews
Easiest way to make a low backlash feed screw is to cut the thread groove to depth but a bit narrow. Then trim off one side of the Acme thread until the nut fits real nice. That way you can see WTHIGO and make a good job. Use plenty of spring cuts! Only disadvantage is that you can't use the angular in feed method 'cos you need to keep the top slide parallel to the bed to adjust the longitudinal setting of the tool bit when trimming the sides. Best to rig up a dial gauge to measure the exact movement of the slide. Its a good excuse to fit a slide lock screw too. Friend John says this was the way that they finished off the feed screws on the CVA tool room lathes, better than 5 tenths backlash was expected all down the screw before the nut adjuster was fitted! When adjusted nominal zero lash on the test rig! If you do things this way the odds are that you can get away without re-making the nut. Has to be very, very seriously worn to be unusable with a screw made to fit. Normally the screw wears faster than the nut and gets to the point of no return long before the nut has had it. Having made the screw to fit its very easy to see just how worn the nut actually is. Naturally if you do decide to make a new nut with a proper size thread there is plenty of meat left on the screw to make it fit the replacement nut. Personally I'd push the boat out and buy a tap to do a new nut rather than fiddle about trying to do a super accurate internal threading job. Still have to roughly thread it first but the tap finishes it off dead right for you. Clive (23419)

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