Sam Thompson Posted July 26, 2011 Share Posted July 26, 2011 I know this is lathe-related but it's really just a metalwork problem.Can any one help with this: I've just broken the nut on the cross-slide feed screw of my lathe; it's a 1920s Erlich, badged IXL, identical to the pale blue machine at the bottom of this page:http://www.lathes.co.uk/ixl/index.html The original part was cast iron and has cracked into three. The thread is 7/16 11tpi Whit. Left-hand. The preferred spec for this dia. is 14tpi and taps for this are available, however... I've brazed the old one together and it seems to be ok but I doubt it's going to last for ever! Quote Link to comment Share on other sites More sharing options...
knots Posted July 26, 2011 Share Posted July 26, 2011 That is a beautiful old Lathe. If you silver brazed the nut the repair is likely as strong or stronger that originally manufactured. If it works and the tolerance is acceptable so that it is not to tight or loose it will at least buy some time to either fabricate, machine, or find a replacement part. A couple of years ago a ball nut in the steering box of my old tractor broke. Parts were not available from the manufacturer so I silver brazed it back together and reassembled the ball nut and steering box and installed it back in the tractor . I used the repair for two years before finally locating anew steering column assembly. The repair was not ideal because the box was basically worn out, but the repair bought me some time to locate a proper new part. The silver braze held. Good luck. Quote Link to comment Share on other sites More sharing options...
Jacques Posted July 26, 2011 Share Posted July 26, 2011 If you a make a new one and put it on the shelf the repaired part will last forever. If you don't make a new one the repaired part will break on a Saturday afternoon with a Monday deadline. How lucky do you feel? :) Quote Link to comment Share on other sites More sharing options...
Sam Thompson Posted July 26, 2011 Author Share Posted July 26, 2011 If you a make a new one and put it on the shelf the repaired part will last forever. If you don't make a new one the repaired part will break on a Saturday afternoon with a Monday deadline. How lucky do you feel? That's it in a nutshell! It also might be quite fun to try and cut the thread on my cousin's lathe. Quote Link to comment Share on other sites More sharing options...
John B Posted July 26, 2011 Share Posted July 26, 2011 That's it in a nutshell! It also might be quite fun to try and cut the thread on my cousin's lathe. If you have yours working, why not cut it on your own? Do you have a picture of the damaged item? The 11 tpi was used for a purpose, and are you sure it is 11, not 10 tpi? The reason I say this is one rotation @ 10tpi moves crosslide in 0.100" which should tie in with the numerals on the dial Quote Link to comment Share on other sites More sharing options...
Glenn Posted July 26, 2011 Share Posted July 26, 2011 Your a blacksmith with a now working lathe. Make the nut your own self. Why not ask an IForgeIron member in UK to look up the nut and ship it to you? Be generous with your reimbursement for their time and effort. Quote Link to comment Share on other sites More sharing options...
Sam Thompson Posted July 27, 2011 Author Share Posted July 27, 2011 I should have taken some pics of it but it's now back in place; it's just an oblong block of CI with a hole through it. It's definitely 11tpi; I know that's weird. I cant cut it on this machine as I cant reverse it. It's not likely that anyone here in the UK will have a spare nut as the lathe is 85 years old and German. Even without the X-slide feed it was still possible to use the machine by locking it up with the gib strip and using the top-slide as a feed but it's not the same somehow. Quote Link to comment Share on other sites More sharing options...
pkrankow Posted July 27, 2011 Share Posted July 27, 2011 so it is left handed? Just set the gears as a tumbler to reverse direction, you add an extra idle gear in the change gears to reverse the direction of travel. Phil Quote Link to comment Share on other sites More sharing options...
Sam Thompson Posted July 27, 2011 Author Share Posted July 27, 2011 so it is left handed? Just set the gears as a tumbler to reverse direction, you add an extra idle gear in the change gears to reverse the direction of travel. Phil That won't work, the tool will feed towards the tailstock. To cut LH thread the work needs to rotate backwards, the tool needs to be mounted the right way up on the opposite side and feed towards the chuck. A lathe will not cut a perfect Whit thread form anyway as the crests and troughs should be rounded. Quote Link to comment Share on other sites More sharing options...
John B Posted July 27, 2011 Share Posted July 27, 2011 A lathe will not cut a perfect Whit thread form anyway as the crests and troughs should be rounded. Thats only true when single point cutting. Chasers were used to finish to shape the thread's profile Formators and carbide inserts will produce rounded crests and troughs. Quote Link to comment Share on other sites More sharing options...
Sam Thompson Posted July 27, 2011 Author Share Posted July 27, 2011 I don't think they make chasers small enough to go into a Hole that small, do they? I've never chased an internal thread; the possibilities for catastrophic breakage financially terrifying! The correct tap is only £356+vat.. . Quote Link to comment Share on other sites More sharing options...
pkrankow Posted July 27, 2011 Share Posted July 27, 2011 The correct tap is only £356+vat.. . Sounds like you can have that part made for that by a shop with the correct tap in inventory for the price of the tap! Phil Quote Link to comment Share on other sites More sharing options...
peacock Posted July 27, 2011 Share Posted July 27, 2011 If you have acess to a lathe that will cut a left hand 11tpi make a new nut and cross feed screw of a form that is easier to cut. That lathe won't care if it has an American standard thread Quote Link to comment Share on other sites More sharing options...
Sam Thompson Posted July 28, 2011 Author Share Posted July 28, 2011 I really don't fancy my chances of cutting an accurate 15" long thread thread on stock that size. Apart from the accuracy, with no powered reverse or thread dial, winding the tool back to the start by hand could become irksome! The "nuclear" option is to find a similar feed screw and nut from a scrap machine and modify it to fit mine. In the mean time, I'm going to try and make a tap out of ms and case harden it. The lathe won't care what the thread is but the micrometer will. Quote Link to comment Share on other sites More sharing options...
fciron Posted July 28, 2011 Share Posted July 28, 2011 That won't work, the tool will feed towards the tailstock. To cut LH thread the work needs to rotate backwards, the tool needs to be mounted the right way up on the opposite side and feed towards the chuck. A lathe will not cut a perfect Whit thread form anyway as the crests and troughs should be rounded. Feeding towards the tailstock is what you would want. That would be a left hand thread: turning forward, but moving backwards. It is not necessary to run the lathe backwards. I'm not necessarily advocating it. Might be just as easy to get a similarly sized screw and nut and fit them to your lathe. I'm not familiar with UK suppliers, but it's pretty simple to buy acme threaded stuff in the US. Quote Link to comment Share on other sites More sharing options...
Sam Thompson Posted July 28, 2011 Author Share Posted July 28, 2011 Feeding towards the tailstock is what you would want. That would be a left hand thread: turning forward, but moving backwards. It is not necessary to run the lathe backwards. This would be OK on an outside thread, you could turn a short length near the headstock to the minor dia and start there; for an inside thread, the tool would need to start the cut blind, there are many opportunities for frightfulness. The thrust bearings on both Mandrel and lead screw are designed to work in the opposite direction and although with work this light, it's unlikely to make much difference, inaccuracies coud creep in. Quote Link to comment Share on other sites More sharing options...
jeremy k Posted July 28, 2011 Share Posted July 28, 2011 Sam - keep in mind that this was done 85 yrs ago, so today it should still be able to be accomplished, you just need to search for a shop that would be willing to do a smaller project as this. Plenty of retired machinists would be thilled to use there knowledge and skill to do this, as lots of them have shops at there homes to play in. Quote Link to comment Share on other sites More sharing options...
Bentiron1946 Posted July 28, 2011 Share Posted July 28, 2011 What was once possible yesterday is not possible today, is that what you're trying to tell us Jeremy or that is takes a really old ancient phart to do it? :rolleyes: Quote Link to comment Share on other sites More sharing options...
fciron Posted July 29, 2011 Share Posted July 29, 2011 This would be OK on an outside thread, you could turn a short length near the headstock to the minor dia and start there; for an inside thread, the tool would need to start the cut blind, there are many opportunities for frightfulness. The thrust bearings on both Mandrel and lead screw are designed to work in the opposite direction and although with work this light, it's unlikely to make much difference, inaccuracies coud creep in. Ooops. Yes, many opportunities for frightfulness indeed on the inside thread. I think your strategy of making a tap might be the surest method. Quote Link to comment Share on other sites More sharing options...
pkrankow Posted July 29, 2011 Share Posted July 29, 2011 What is the minor diameter, 1/2? What is the depth? 1 1/2 inch? That is pretty tight. Best of luck with the tap, I don't think I would try boring threads that small. Phil Quote Link to comment Share on other sites More sharing options...
Sam Thompson Posted July 29, 2011 Author Share Posted July 29, 2011 Sam - keep in mind that this was done 85 yrs ago, so today it should still be able to be accomplished, you just need to search for a shop that would be willing to do a smaller project as this. Plenty of retired machinists would be thilled to use there knowledge and skill to do this, as lots of them have shops at there homes to play in. It was the retired engineer down the road that suggested making a tap! Thank-you everyone for your help and suggestions. Quote Link to comment Share on other sites More sharing options...
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