Fixed my sticky Shars QCTP.

ChrisAttebery

ChrisAttebery

Rocket Nerd
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Jan 11, 2018
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I've had my Shars BXA/250 sized tool post for a couple years. It's had a persistent issue where if I tighten the top nut to lock the tool post in place the release lever would get stiff. I usually just backed off the top nut a bit and it was fine. Occasionally the toolpost would move though. Today I took a look at it and decided to unscrew the barrel nut that goes through the center of the tool post. I measured the depth of the nut and the depth to the shoulder that the nut is supposed to seat against. They were almost exactly the same. I measured the OD of the threads and barrel and put it all back together. I turned a piece of brass and parted off a few shims of different thicknesses. After a few attempts I found that a .007" allowed the barrel nut and top nut to be cranked down and still left the quick release handle free to move.
 
Thankyou. My BXA does the same thing, and I have been dealing with it the same way..... trying to remember to jam down the nut before a heavy cut. I did take mine apart once hoping it was just a touch of grit, but no luck. I had vowed them to shim it.... that was two years ago.
 
I fixed my Shars BXA this past weekend. No pics, sorry.

Rather than trying to make shims to go under the barrel nut, I decided to dress underside of the top flange. So I found the proper collet and set the nut up in the lathe. I then proceeded to.... ummm... errrrrr, remove it from the lathe and set it up in the mill. Spun it up to umpteen zillion RPM, and dressed the flange with a file. I removed about 0.004" total. It now works very smoothly no matter how tight the center nut is.
 
LOL! That sounds like something I would do. I'm glad you got yours sorted out.

RandyWilson said:
I fixed my Shars BXA this past weekend. No pics, sorry.

Rather than trying to make shims to go under the barrel nut, I decided to dress underside of the top flange. So I found the proper collet and set the nut up in the lathe. I then proceeded to.... ummm... errrrrr, remove it from the lathe and set it up in the mill. Spun it up to umpteen zillion RPM, and dressed the flange with a file. I removed about 0.004" total. It now works very smoothly no matter how tight the center nut is.
Click to expand...
 
I understand that we are talking about the piston style QCTP. My Phase II tool post started to bind too if the nut was too tight. It looked like the shoulder at the bottom of the bore in the body is worn unevenly. This causes the bolt sleeve to put pressure sideways against the cam barrel.
Not sure how to go about taking a cut down in the bottom of the bore to set the shoulder square again.
 
Mine is a wedge style. But the basis is the same. The barrel nut holds in the cam/worm barrel that drives the retainers.
 
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