Finally got my new adjustable chuck mounted

[tmc_31]

Hey guys,

I finally got my new Fuerda (gator) 8" 3 jaw adjustable chuck mounted today. The back plate was about .010 out at the face and .007 out of round. I trued those up and got a nice fit up with the chuck. It took a while to dial it in and I am not sure I am doing it right. I chucked up a 1.25" TGP test bar and with the 6 mounting screws around the face of the chuck just snug, dialed it in to within .0005. When I tightened up the mounting screws the run out went to .003. Not too bad but I was hoping for better. I tried it again and after going though the process again, I got it down to .0015. Ok I can live with this but when I re-chucked the test bar, the runout was .0025. I really thought the repeatability would have been better than that.

What has your experience been with these adjustable chucks? It there a certain order that these things should be tightened up? The chuck will do what I wanted it to but I would like to be able to get the most out of it that it has to offer. Any insights or suggestions will be appreciated.


Tim

[Willy]

Did you tighten the bolts in a pattern such as this?

http://www.goodhousekeeping.com/cm/goodhousekeeping/images/WheelPatterns.JPG

Sounds as if the face is true, but the distortion created while tightening the bolts is causing the problem. I would not think the chuck would be an issue but at this point everything is suspect.

[macona]

I never tighten the 6 bolts all the way. Just tight enough to allow it to slide. All they need to do is keep the chuck on the plate. The four adjustment screws will keep it concentric.

Also lathes cut a face concave by design. So that might be an issue here, especially if the cross slide is worn.

[tmc_31]

Willy, on the first attempt I just tightened the screws around the face. On the second attempt (with the better result) I tightened them like the six hole pattern shown.

I wonder if using a torque wrench would help?

Tim

[Willy]

Yes by all means use a torque wrench to ensure consistency.
I have never really used very much torque for them, usually about 100-120 inch pounds at the most.

[tdmidget]

Macona has it right. Just like a boring head, you want them tight enough to hold but still adjustable.

[tmc_31]

Sooo... Macona and tdmiget, what I understand you to be saying is that the mounting screws should be snug, but just loose enough to allow the adjustment screws to do their thing? Then once the least run out is achieved no further tightening of the mounting screws is required? Have I got it right?

thanks

Tim

[photomankc]

Yep, that's how I do my Bison 3 jaw adjustable. I can get it down to just a wiggle on a single setup and usually it will hold under .001 for most anything else I chuck up. It's not for hogging or heavy cutting but it does fantastic for light to medium work with the set screws doing the work of holding the position.

[becksmachine]

When you re-chucked the test bar, did you use the same hole/pinion to tighten the chuck?

Dave

[tmc_31]

Dave, this chuck only has one pinion.

Tim

[becksmachine]

Ok, that certainly eliminates that possibility.

Dave

[macona]

Yep, you have it. Just snug enough so it will move with the adjusting screws.

Even with this I had to grind the jaws on my chuck to be where the should be. And this was a NOS Buck. Heck, when I got it only 5 of the 6 jaws would come in contact.

[tmc_31]

Macona, I have heard it said that in a 6 jaw chuck the work piece has to be pretty close to round. I originally wanted a 6 jaw, but for this reason and the fact that most of what I got it for was working with solid stock.

Thanks for your advice on this.

Happy new year,

Tim

[macona]

Technically it should be more round than a 3 jaw. Like a 3 legged stool, it will never rock.

6 Jaws are good for softer things like tubing and plastics where you have to worry about deformation. It is the #1 used chuck on my lathe. Some say not to use them as a general chuck but if I crash the machine hard enough to mess the chuck up that badly then its going to be a lot more I have to worry about than the chuck.