Can't get Clausing 100 mk IIIa to cut a with out a taper????

[hvontres]

Took your advise and redid the test bar to your suggestion. I don't really under stand why to only the .001 passes. I always take take 25-30 thou ruff cuts and 2-5 finish cuts if needed. Any way I kept working on the lathe went back and checked ever thing twice to make sure it was tight and level reran a test cut and I'm down to 0006"/ft taper and that is more than good. Let the lathe set over night and went back out and remounted the test bar, and did another cut for repeatability and measure .0007 so that is good for me. Now I am working on the round out problem. Which is now down to .002 but still I think I should do better with a Bison chuck.
Thanks for all your help guys. I may be back about the run out.
CH

The .001 for the test bar cuts is to keep the bar from flexing when you take the cuts far from the chuck without a center in there. The idea of the test it to only measure taper caused by bed twist, not tool forces. If you have a large, unsupported part far from the chuck and take heavy cuts, the tool pressure will cause the part to bend away from the tool and the cut will be shallower, resulting in a larger OD than near the chuck where the part can't flex as much. This will then show up as "Taper" in your measurements and cause you to chase your tail while trying to get rid of it.

When you are making a real part of this size you would use either the tail stock or a steady rest to support the far end and give the whole setup more rigidity. But even then, if you need a really straight part you might want to take a really light final pass to make sure the whole length of the part is a straight as can be. I have also noticed the opposite effect when using a long boring bar to make a deep hole. The bar will deflect away from the work and won't take the full depth of cut you dialed in the first time. Once you get close to size, it's a good idea to take a second "spring" pass without changing the cross feed. this will usually take another .002-.003 off of the part on my lathe.

Hope this helps, and happy swarfing

 

[Don B]

The .001 for the test bar cuts is to keep the bar from flexing when you take the cuts far from the chuck without a center in there. The idea of the test it to only measure taper caused by bed twist, not tool forces. If you have a large, unsupported part far from the chuck and take heavy cuts, the tool pressure will cause the part to bend away from the tool and the cut will be shallower, resulting in a larger OD than near the chuck where the part can't flex as much. This will then show up as "Taper" in your measurements and cause you to chase your tail while trying to get rid of it.

When you are making a real part of this size you would use either the tail stock or a steady rest to support the far end and give the whole setup more rigidity. But even then, if you need a really straight part you might want to take a really light final pass to make sure the whole length of the part is a straight as can be. I have also noticed the opposite effect when using a long boring bar to make a deep hole. The bar will deflect away from the work and won't take the full depth of cut you dialed in the first time. Once you get close to size, it's a good idea to take a second "spring" pass without changing the cross feed. this will usually take another .002-.003 off of the part on my lathe.

Hope this helps, and happy swarfing

A very good description...!)

 

[COMachinist]

Hi All
I'm still not sure what I did to get it to cut with min tapper. I did end up with the lathe out of level cross ways to get the taper out. Other than that I have no clue but it is repeating with good numbers. I'm working to get the TIR down to a manageable level now .001 should be doable. Stat tuned for that.
Again thanks to all
CH

 

[Vince]

Just my .02, When I level a machine I do not go across the v ways. I stay on the flats.
I made the mistake of leveling across the v's on my Clausing and could not figure out why I was getting a taper cut.
Upon closer examination I found that the v's are not the same. They looked the same but were actually not.
I have run across this quite a few times since, some machines you can actually see the difference but others are really hard to tell.
Vince