Stiffness of Spindle Extending on PM-935TV

[MensaPE]

You know how it is, the field guys always looking for shortcuts!!

But, quick and perfection is the holy grail, right?

 

[MensaPE]

UPDATE: Finished the copper lap for the quill, ID within 1 tenth. Starting boring, finish was terrible until a little spritz of WD40, then it was wonderful. Used push and pull screws to change size slightly. Very fortunately, cutting the gap did not release any internal stresses, was worried it would grab the slitting saw. Put it on the quill, without lapping compound, and learned something new! In the case of expanding the lap, realized that the expansion is not simple linear....Highest bending moment is directly opposite from the gap, going down to zero bending moment at the gap, so the radius does not change near the gap...my mind image is a hinge directly opposite from gap...If I had a wire EDM, would cut radial slots 1/4 in apart all around the inside (maybe outside using slitting saw?) of the ring, to make it super flexible, then would only need the puller screw.
Also realized that 2 or 4 micron diamond powder is way too fine, would leave a polished surface with hardly any oil storage volume in finish scratches, existing finish is ground, seems like maybe 220 grit finish, 'grooves' aligned around the quill. I'll get some fine auto valve lapping compound, and try that. Since this is taking so long, tried 400 wet or dry with WD40 (like a shoe-shine), but couldn't measure any change after 1/2 hour of sanding.

 

[MensaPE]

Update, tried rotating lap by hand with fine engine valve grinding compound, so slow and without measurable results after a long effort. Then, came up with the bright idea of having the mill drive the lap. WHOOPS! The copper gaulded(?), created a few furrows in the quill, fingernail deep. CRAP! Brighter idea, 220 grit 3M Wet or dri paper, spray glue to hold it to inside of lap (lap ID increased to 3.380 to accommodate 12.5 mil thickness of paper, WD40 lubed. After 20 minutes, stopping, moving lap up, down, run for a minute, move, run again, the furrows are much less noticeable, diameter reduced a tenth. Fluids are black...Q: Is chrome abrasion product black? Paper still feels sorta new, abrasion wise. Paper slipped around 90 deg, so cleaned and put on a new sheet of the 220 grit. I love the 2 screws for contracting/expanding the lap.
Note: Tried uploading a 5.3MB video, but no image showed, only sound.

 

[extropic]

I'm concerned that the wet-or-dry SC 220 will leave sharp peaks in the surface texture and the peaks will wear away (relatively) quickly leaving the quill under your target dimension. If it's not too late, how about getting the OD down to within a tenth, then switch to 1000 grit to smooth some peaks for the last tenth.

As you suggested earlier, it doesn't make sense that the quill was mushroomed by the drop. I'm wondering if you tried the quill full range of extension before the drop. I suspect the taper in the quill OD is most likely a manufacturing defect rather than drop damage.

 

[verbotenwhisky]

I believe, if you haven't already, I would pull the quill and set it on a granite plate and use a DTI to check it to insure it is straight, not bent. it would not take much of a bend to create the stiffness.

 

[MensaPE]

I'm concerned that the wet-or-dry SC 220 will leave sharp peaks in the surface texture and the peaks will wear away (relatively) quickly leaving the quill under your target dimension. If it's not too late, how about getting the OD down to within a tenth, then switch to 1000 grit to smooth some peaks for the last tenth.

As you suggested earlier, it doesn't make sense that the quill was mushroomed by the drop. I'm wondering if you tried the quill full range of extension before the drop. I suspect the taper in the quill OD is most likely a manufacturing defect rather than drop damage.

Yeah, I'm thinking the same that it was a manufacturing thing. There's a sticker on the front of the quill housing, I'll take a picture and post later...maybe it refers to the mfg data. I like your idea of going to the finer grit for the finishing touch. Much higher contact surface area with the finer grit (after minimal 'wear-in'). Just less lubricant holding volume.

 

[MensaPE]

I believe, if you haven't already, I would pull the quill and set it on a granite plate and use a DTI to check it to insure it is straight, not bent. it would not take much of a bend to create the stiffness.

OH! I hadn't thought about a bend! All I can measure 'in situ' is a larger diameter, like a bugle, about 4 tenths larger on the bottom 2" of the quill.

 

[MensaPE]

I'm concerned that the wet-or-dry SC 220 will leave sharp peaks in the surface texture and the peaks will wear away (relatively) quickly leaving the quill under your target dimension. If it's not too late, how about getting the OD down to within a tenth, then switch to 1000 grit to smooth some peaks for the last tenth.

As you suggested earlier, it doesn't make sense that the quill was mushroomed by the drop. I'm wondering if you tried the quill full range of extension before the drop. I suspect the taper in the quill OD is most likely a manufacturing defect rather than drop damage.

Wish I had checked it before the drop. Head was angled way down for lower packing height....Just dropped it :-(, professional righting, raised head up to vertical, then tried up and down.

 

[verbotenwhisky]

OH! I hadn't thought about a bend! All I can measure 'in situ' is a larger diameter, like a bugle, about 4 tenths larger on the bottom 2" of the quill.

to check that I think you'll need to pull it out.

 

[MensaPE]

to check that I think you'll need to pull it out.

Since starting with the 'lapping' process, quill is not as stiff as it initially was, so I'll hold off pulling it.