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

[COMachinist]

Hi All
Happy birthday to America.
:happybirthday2:
I have a new Bison 8" fixed jaw chuck I have just mounted, and I can't get it to cut a test pieces with out the outside ring from being .004 smaller than the ring up next to the chuck. The chuck has about .007 run out 2 out from the jaws.
I turned the back plate to size and faced the back plate. I checked the back plate for run out and the face for wobble but it did the .0001 Starret DTI hardly moved. I turned the spigot so it is a snug fit with a little pressure and used Transfer screws to get the mount holes marked and drilled them on my mill. The mount SCHC screws fit with no binding. I have checked every thing I could think of. The spindle only has about .0001 run out and no front to back looseness.The preload on the spindle is set to factory specs. I have checked the level on the lathe with my Starret master level and it is with .0005 from head stock to tail stock end cross wise and .0012 length wise. I debured the Bison jaws cleaned and lubed the scroll. I'm just kind of at a loss now. Any ideas??? I loosened and tied to see if I could tweak the head stock but it is fixed because of the V rail. I would like to get this figured out so my son can help with the work, I can't lift any thing for another two weeks so while he is hear, free labor :lmao:. If I can't figure it out then it will have to wait a few weeks longer. Oh it has the same run out and run out both sets of jaws?
Thanks
CH

 

[Don B]

Unless I'm misinterpreting your description your dealing with 2 separate problems, even though you used a level it sounds like you have a twist in the bedways, it sounds like you need a shim under the the rear mounting location (tailstock end) , sorry I'm not familiar with this chuck I'll let someone who might be comment on it.

 

[JimDawson]

0.007 run out sounds like quite a bit. Bison chucks are normally pretty good. I would put an indicator on the chuck face and see what the run out is there. It almost sounds like the chuck internally is not parallel with the mounting surface.

I think you did everything correctly, and you have good measuring instruments to work with, so I don't think the problem is there.

Is your test bar supported by a center on the outboard end? If so it could be a tailstock alignment issue.

I guess the worst case is get out the tool post grinder and re-grind the jaws.

 

[COMachinist]

Hi Don
Here is my level readings cross wise. Head stock, center and tail stock areas. If there was a twist wouldn't the level show that. I meanthe bubble on that thing move because the work light heats it up slightly. .0005/foot???? I went back to the chuck that came with the lathe and it has .004 run out and .003 tapper. I put the bison 5c collet chuck on with 12" piece 3/4 drill rod and it has .005 run out and .007 run out in it???? I checked the spindle and the nose and thread stop are all square with in a .0005. My had to head back to his house to get ready for work Monday so I down for a few weeks until my shoulder heals up completely.
:think1:
Thanks
CH

 

[hvontres]

While you are waiting for you shoulder to get back in order, you might want to take a look at a video Tom over at Oxtool made about adjusting bed twist:
[video=youtube;GErhXyUb2Go]https://www.youtube.com/watch?v=GErhXyUb2Go[/video]

Also, one other thing to keep in mind is that you are measuring the straightness at the top of the V-s. The surfaces that control the relationship of the tool to the spindle are actually the sides fo the front V and the rear flat way. So while the top may be fairly straight, there may be some wear on the critical surfaces that might be causing some tapering.

And if you are turning with a center and the tail stock isn't aligned, then you might also get some tapering. In fact, purposely offsetting the trail strock is one way to turn a taper on purpose

Good luck and I hope the shoulder is better soon

 

[Andre]

Before you click the link, I just want to make sure you know I'm not saying your doing something wrong or suggesting you do things in a different way. I'm just posting this as a reference.

[h=1]
Leveling and Setup of the Metalworking lathe Part 1[/h]https://www.youtube.com/watch?v=zIDL77qt1tI

[h=1]Leveling and Setup of the metalworking lathe P2[/h]https://www.youtube.com/watch?v=GErhXyUb2Go

 

[Don B]

Hi Don
Here is my level readings cross wise. Head stock, center and tail stock areas. If there was a twist wouldn't the level show that. I meanthe bubble on that thing move because the work light heats it up slightly. .0005/foot???? I went back to the chuck that came with the lathe and it has .004 run out and .003 tapper. I put the bison 5c collet chuck on with 12" piece 3/4 drill rod and it has .005 run out and .007 run out in it???? I checked the spindle and the nose and thread stop are all square with in a .0005. My had to head back to his house to get ready for work Monday so I down for a few weeks until my shoulder heals up completely.
:think1:
Thanks
CH

Well I'm not saying that shouldn't work but I'd be curious how level it is off the flats, you'd need 123 blocks or something similar and use them in the same position when moving them up and down the bedways, also put a tick/reference mark on the level with a marker or something for positioning, don't rotate the level, use it in the same direction and relative position when moving it up and down the bedways, give that a try and see what results you get.

Edit: my apologies I forgot to add this, those surfaces you're indicating/leveling from are not critical surfaces and may have been treated as such during the machining proses.)

 

[Bradrock]

If it's bed twist or the tailstock, Why is one chuck better than the other?

 

[Don B]

If it's bed twist or the tailstock, Why is one chuck better than the other?

Sorry I only see a reference to 2 jaws not chucks, the chuck will not produce the taper if it's inaccurate it will cause eccentricity between your original diameter of your chucked stock and the new diameter your turning, I see this as 2 separate problems, runout on the chuck is one and a taper issue which is separate, it sounds though as if the chuck back plate mounting procedure was done properly and I'm not familiar with Bison chucks so I'm sure what to say about the chuck part without more info.

Edit: if the jaws are not parallel to the center of the spindle this could also cause original diameter of your chucked stock to be un-parallel (if that's even a word) with the new diameter you're turning, parallelism and any eccentricity can be corrected by regrinding the jaws.

 

[Bradrock]

"I went back to the chuck that came with the lathe and it has .004 run out and .003 tapper."