Heavy 10 Cross Slide Backlash
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Don Verdiani
Oh, South Bend wise people,
I still have a strange little problem with my Heavy 10. Feeding in with the cross slide works just like you would expect. Feeding out, like say cutting an internal bore/thread, there is a small amount of “spring”, for lack of a better term. I have a taper attachment, but I don’t think that’s the issue. There is clearly backlash in the cross slide, as I can pull/push the compound and get a 0.015” in-out movement. That’s probably problem 1. Still, the little elastic spring when feeding out is weird. I go to make a cut, and set the dial for 0.020”. The dial springs back to indicate a 0.018” cut, and the actual cut is somewhere in-between. Not a big deal, and I can easily do decent work now that I understand it, but I would love to have it go away. Anyone every have this happen?
Before I buy a new cross slide nut, I wanted to ask. I used to see cross slide and compound nuts with a built-in backlash adjustment capability, but I just searched amazon and ebay and found no mention of them anymore. Anybody know anything about these things? Can I make one?
Don Westtown, PA |
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Look for that sort of info on the 7x Mini-Lathe groups. Several folks using those machines have done that because of the weird way they adjust for backlash. https://gadgetbuilder.com/MiniMods.html Go on down the age a bit and see how John Moran handled it. Bill in OKC William R. Meyers, MSgt, USAF(Ret.) Aphorisms to live by: Good judgement comes from experience. Experience comes from bad judgement. SEMPER GUMBY! Physics doesn't care about your schedule. The only reason I know anything is because I've done it wrong enough times to START to know better
On Thursday, February 9, 2023 at 02:13:06 PM CST, Don Verdiani <dlverdiani@...> wrote:
Oh, South Bend wise people,
I still have a strange little problem with my Heavy 10. Feeding in with the cross slide works just like you would expect. Feeding out, like say cutting an internal bore/thread, there is a small amount of “spring”, for lack of a better term. I have a taper attachment, but I don’t think that’s the issue. There is clearly backlash in the cross slide, as I can pull/push the compound and get a 0.015” in-out movement. That’s probably problem 1. Still, the little elastic spring when feeding out is weird. I go to make a cut, and set the dial for 0.020”. The dial springs back to indicate a 0.018” cut, and the actual cut is somewhere in-between. Not a big deal, and I can easily do decent work now that I understand it, but I would love to have it go away. Anyone every have this happen?
Before I buy a new cross slide nut, I wanted to ask. I used to see cross slide and compound nuts with a built-in backlash adjustment capability, but I just searched amazon and ebay and found no mention of them anymore. Anybody know anything about these things? Can I make one?
Don Westtown, PA |
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At one point in the life of my Atlas 10” lathe years ago, I modified the cross feed nut by saw cutting across the nut part way through the height and all the way through the Acme threaded hole. Then drilled a clearance hole in the end and tapped the other half for a small diameter socket head cap screw in order to be able to ‘pinch’ the Acme thread. Idea is to reduce the backlash. As I recall it did improve the backlash somewhat. I have since replaced that cross slide nut with a new one. Might be something you might want to investigate and try. Hope my written description makes sense. If not, I can draw a sketch. Might be just as easy to purchase a new nut and install that. Note that a new nut won’t necessarily get rid of all the backlash depending on how much wear there might be in the thread on your cross feed screw. The thread tends to wear more in the middle of the length than at each end.
Steve Haskell Troy, MI |
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The SB Heavy 10 had several dial options. The small dial and several Large dial configurations. It would help to know which dial you have. Often play, particularly on the small dial is not in the nut but in the screw mounting. You can usually check for this with a feeler gauge.  If you find some play here, let me know and I can show you how to correct this. The larger dials often, have thrust bearings. They can be preloaded to remove the axial play. If these are bad they can be replaced. Boston Gear sells a suitable replacement. Also check to be sure the nut is properly secured in the hole. I have hade mine loosen. As I remember the Heavy 10 cross slide screw is a 7/16-10 Acme thread. Its just a bit small to single point. The depth of the thread is 1/2 the pitch plus 0.01” clearence. The ID would thus be. 0.4370 -0.100 -0.020=0.3175”. since the tool would need to extend at least 0.060, past the holder. The maximum body of the holder could be 0.2575”. I have made some 1/2-10 Acme nuts for my Burke Mill,  The little nib you see sticking out of the boring bar is a shop made acme bit. It’s adjusted to just have enough depth to cut the thread. The picture dates from 2009 so memory may be bad BUT it think its a 1/2” boring bar. I do remember turning one down later so (perhaps) 7/16 is possible. Finally, remember, if the nut is worn, so is the screw. Perhps not as much, but worn. Jim B. 1629 Riverview Drive. Apt 416 Deerfield Beach, FL 33441
-- Jim B |
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