z Axis Woes

[Mosey]

I am having trouble getting accurate z axis depth on my Clausing 8525 Mill. The quill comes down to the top of a nut to set the depth of the cut. That nut locks, but no matter how careful I am, the mill doesn't stop accurately, and the depth of cut varies by 0"-2/3 thousands. If I am very careful and bring the quill down with the same force every time, the depth varies by a few tens up to a few thou, each time a little different. I am sure to lock the adjuster nut. What to do?

 

[ShedBoy]

I have the same issue with my Bigport, never seen a Clausing in oz. I will be interested to see what people recommend. Love the light around the quill.
Brock

 

[Mosey]

That light is a Staples $15.00 circular fluorescent with magnifier. Pop out the mag glass with 3 screws, and you've got it. Have to make a better mount for it to attach to the side of the mill.
I can't believe the BP has similar problems.

 

[my65pan]

I'm not sure about a Clausing, but to solve this problem on a Bridgeport I put a spacer under the quill nut and lock nut and then tighten them both down on top of this spacer. This way the quill nut is supported by the head casting rather than the little c-clip at the bottom of the quill stop. What happens is the c-clip that keeps the threaded rod part of the quill stop from dropping out the bottom of the casting flexes when you pull the quill handle down against the stop.

 

[ShedBoy]

I can't believe the BP has similar problems.

Bridgeport clone marketed by Hercus in Oz early 80's. Most people don't spot the spelling difference. It done 25 years at an engineering shop before I got it. It has more issues than just a dodgy z axis :big: :big:

Brock

 

[Mosey]

I wish it were that way, but I think I have isolated the problem.
There are only 5 or 6 parts involved. There is a micrometer Depth Dial at the top.
It is attached to the top of a long vertical threaded shaft, which you turn to run the bottom of 2 half-horseshoe nuts up or down the shaft. The top nut turns with the Dial above and stops against the bottom nut to stop your depth.
There is a little brass lockscrew to keep the shaft from turning.
The top half horseshoe nut is bolted behind into the quill.
That is the problem, as there is the entire weight of the quill torquing that little nut. It's bolt into the quill isn't enough to resist the weight of the quill. It wiggles.
I may have to pull it all apart and really tighten that bolt into the quill, and locktite it.
I have drilled the top nut for a DRO attachment, but if the nut isn't tight, DRO won't be either.
Check the pictures and watch me weep.

 

[ShedBoy]

I'm not sure about a Clausing, but to solve this problem on a Bridgeport I put a spacer under the quill nut and lock nut and then tighten them both down on top of this spacer. This way the quill nut is supported by the head casting rather than the little c-clip at the bottom of the quill stop. What happens is the c-clip that keeps the threaded rod part of the quill stop from dropping out the bottom of the casting flexes when you pull the quill handle down against the stop.

my65span
Any chance you could post a pic of that? Having trouble visualising it.

Brock

 

[jonesie]

what i have done for 40+ years is put something under the quill stop and then run stop down to it and lock then i bring the mill up to part and get a touch then raise quill and move table up required depth, then lower quill back down to depth. you will repeat better as the quill is now coming down to a good solid stop.you will always get some spring but should repeat within .001. good luck jonesie

 

[Mosey]

I believe that the problem is that the quill stop is loose in the quill, therefore, problem will not go away until stop is tightened in the quill. I intend to tighten the stop and will let you know how this affects the accuracy.

 

[Ken I]

Mosey, I agree with Jonsie as the only way to get really close.

Your are right about the quill stop - the stop ring on my Standard (BP knockoff) was loose and completely screwed up the stop's accuracy - quite a bit of work to strip and put right.

With this fixed the quill auto stop now seems really accurate - but I would never rely on it - go to dead-length after setting a'la Jonsie.

Ken

 

[Mosey]

Yes, you are right. I always peck away at the final depth. As it is now, though, if you are at 1.005" and you want 1.000", you can't dial down another .005 because you might get .007" or .003. (It never takes less than you want, does it).
Fixing it is a pita, but there is no alternative.

 

[Mosey]

Tightened up the quill bearings with my home-made tightening tool, just a tiny snug up, and the vertical play is down to a few tens. That depends on my setting the quill down against the stop gently, and Consistently with the same feel! Maybe I leave well enough alone until I feel like tearing the pulleys off the top of the spindle.
Tightening tool looks like a 2" x 1/4' x 12" steel plate, with 2 dowel-pins and a big hole to fit over the spindle nose.