Advise please on modifying a centre finding microscope

should be advice not advise,

I've a Hauser M1 jig borer than came to me without a centring scope. Perhaps unlike its larger brethren, this machine is often used in such a way that this is a problem.,...so I recently purchase scope for it. The Hauser Z is lapped and each accessory including the spindle is lapped to fit, so a piece from one is very unlikely to work properly in another. The seller of the one I bought was unable to give an exact measurement but we agreed to do the deal and I'd return it if it doesn't fit.

Well, it doesn't fit. The good new is its too large, by about 1.2 thou.

In favour of keeping it is that I'm unlikely to ever find one that is perfect, and I need (well ok, want) one.

Questions

1) If I carefully built an adjustable external lap, can I count on it following the original cylinder shape to a very high degree of accuracy...or is that wishful thinking? I can cylindrically grind (albeit on a motorized workhead equipped T&CG so its not the best set up) but feel that I should have a lapped finish and am thinking 1.2 thou to grind then lap is a really tight allowance. I'm not super experienced grinding; I've been able to get results by creeping up on things with a bit more allowance can get alignment prefect. only 1.2 has me a bit concerned. What would you do?

2) Are there any big risks in taking this apart, i.e. will I destroy some special factory set alignment? I don't know what I don't here so sorry for the dumb question, better to ask than F it all up - anyone taken one of these apart, easy, hard, any tips?

Thanks!

Forget the T&C grinder....most (if not all) lac the rigidity and the precision on the spindle to do what you need.
An experienced grinder hand on a good cylindrical grinder tuned to be grinding true and straight could do this work.

Think a lap properly made and applied could hold truth on the OD..But it would require careful monitoring and working selective spots to maintain straight and parallel.

Not an expert on these scopes, but think if you can avoid disassembly you would be the better for it...Also think that small errors in the scopes alignment can be corrected by adjustments.

Cheers Ross

Ross makes good points.

Before going any further, I suggest you figure out how the scope is adjusted. For example the mechanism on my Hensold-Wetzler scope has four grub screws that work like on a four-jaw independent chuck. Don't worry about putting it out of alignment, because the procedure for alignment in the machine is to make a small mark on a test piece with the tip of a spotting drill, then without moving the axes, insert the scope and shift the cross hairs to the mark left by the spotting drill. You then test this adjustment by rotating the spindle 180 degrees. So once you know how to adjust it, there's no problem in getting it back "on the mark".

Once you have figured out how to adjust, remove the power wiring, and as much else as you can (lights, ocular, ...) without disturbing the core optics. Then build "caps" that go over both ends, with true center mark drillings on them. Block off all entrances with putty and tape, and bring it to someone with a good cylindrical grinder. They will need to grind it wet, so make sure you have really waterproofed it first. You'll need to bring another piece of tooling that's a perfect fit in the spindle so that they can set a snap gauge from it. Removing 1.2 thou with a good finish will take just a few minutes. The hard work is in prepping it, particularly the caps with centers, so that they can just pop it into their grinder and go.

Well, what about centers? How would you arrange that?
Ole

ole.steen said:

Well, what about centers? How would you arrange that?

Click to expand...

I can not say, because I have never seen or held one of these or taken it apart. But the idea is that after taking off the easily removable parts (for example the occular) there will be internal or external threads or machined surfaces which can function as attachment points. So turn and if needed thread a couple of aluminium or steel caps or plugs, one for each end. Get them attached firmly, then put the microscope body with the plugs attached into a lathe (gentle!!) get it centered precisely, face off the plugs or caps, then center drill them. Double check between centers that you have it centered precisely enough (better than the 0.0012" which needs to be removed!). Double check that you have waterproofed everywhere, and then take it to the grinder.

From looking at the photos, it appears that the power cord unplugs and that the upper part does not need to be ground. So the cap for the top part could be a large piece of aluminum which is internally turned to be a snug fit over the large OD part next to the power socket and encloses the entire occular area. Three setscrews with brass or plastic bumpers can hold that secure, or split it 3 or 4 times and use a hose clamp on the OD. At the bottom end, remove the lighting assembly and lower shield, then make an aluminum part which threads in to replace that and can hold a center.

Thanks all. I guess next step is finding someone who's had one apart and can comment on the alignment. I didn't see any way to adjust alignment which made me think maybe it was factory set and not easily reset. I agree if that can identified it makes it a lot easier to get ahead with confidence

If it was easy to take apart, I also thought making a new tube might be a good approach. If the alignment is settable, that might be the easiest way to get the right OD with the internal work at each end aligned and parallel