Thread: Centring Microscopes

Clever - I would not have thought of using a HDD as a mirror.

Michael

Great idea, well executed.

I agree with Michael re not thinking of the mirror idea. I have a couple of disks put aside just in case I think of a use for them.

Dean

A very neat holder Stu

I'm guessing that since the mirror would be incredibly hard to be at exactly 45deg, you can only use it to center on one axis at a time, the one perpendicular to the scope? If you have got the mirror close enough to use on both axis at once that some real neat work!

Cheers,
Ew

Stuart and I were discussing scopes and Stu wondered how a dedicated scope would compare with our Marcels. I was to soon find out. Gregory offered me his Isoma, he being recently mill-less, and I jumped at the opportunity to acquire what was to me, a near mythical accessory for the 13.

Schaublin supplied and still supply Isoma scopes to accompany their mills and lathes. Greg's was an accessory for a Swedish 3R EDM machine. The arbor was 20mm in diameter and featured a cross dowel, something used for alignment I imagine. I had the hollowed out 30 taper arbor I'd made for the Haimer Taster so I had the means to mount the scope in the 13. The dowel required amputation and the arbor, shortening. 8 Dremel cut off discs and 3/4 of an hour latter the arbor was 11mm shorter. Then disaster struck. In my unsuccessful efforts to remove the dowel with a drift and hammer, I dislodged the scope's mirror. I only realised this when I had completed the arbor modifications and had the scope in the mill's spindle. There was no image. Dismantling the scope presented a problem. There was a steel cup or cap shaped thingo inside the barrel that initially defied my efforts to remove it. Beyond it was the mirror/objective lens assembly. My largest small bore gauge provided the solution. The mirror was surprisingly fixed with glue. The glue may have become embrittled, belting things with a hammer must have been the glue's last straw. I refixed the mirror with 5 minute Araldite, a product I have always avoided given its Gumby nature. Its Gumbiness allows it to be cut away should mirror ailments trouble me down the track.

Alignment of the mirror was something else entirely. The Swiss probably used a jig to provide alignment and the assembly is secured with a single 2mm socket set screw. All I had was a mark on the black anodised objective lens barrel for alignment. Viewing that mark through a two millimeter diameter hole was, if anything, imprecise. A whisker's non alignment meant the centreline of the optics in relation to the spindle centreline were out of whack. A lot of painstaking trial and error has fortunately resulted in realignment.

The illumination is clever although finding E5 3.5 volt bulbs may prove a challenge. That's an E10 bulb alongside the E5. The scope has a focusing distance of about 25mm from the face of the ringlight.

Thank you Greg.

BT

Isoma 019 (Large).JPG

Hi BT,
My pleasure.
So it doesnt clear the dogs?

Originally Posted by Ueee

I'm guessing that since the mirror would be incredibly hard to be at exactly 45deg, you can only use it to center on one axis at a time, the one perpendicular to the scope? If you have got the mirror close enough to use on both axis at once that some real neat work!

The jury is still out on that. The 45 needs to be close but there are a surprising number of things that need to either parrallel, square or intersect for this to work as the amount of adjustment in the reticule means you need to get pretty close with the machining. The first time I put it together I couldnt get it aligned, left the shed in a huff. Next day I cleaned everthing down put it back together to get to the bottom of the problem, found the problem had gone. It was working just fine when it left here, only to reappear when it got to the west. I'm pretty sure I know what the issue is, a machining error on the tube for the scope(but shhhh dont tell anyone). Though I've just thought of something else it could be.

MkII will have lights and may have an angled scope.. we'll see(I'm beginning to think its not really needed unless you were doing some really strange like centering a bore with the scope in a boring head with the mills head on such an angle that your head hits the table)

Stuart

Easily rectified Stu.

Centring Scope 002 (Large).JPG

Hi BT,
If I recall correctly the circle is about 30mm? That should fit between your dogs. the area in the green rectangle can(I think) be machine as much as needed to clear the dog, though as I don't have a drawing, I could be wrong lol

Talking about drawings. I don't recall making an allowance* in the machining for the mirror thickness. Now this would mean the point the scope was centered on will be 1.41mm to close to the operator. It was to close in my first test though I didn't measure the error.
This could mean a few things. Either I was very lucky that it lined up in my second test or there is more adjustment in the reticule than I thought.
So if you center the reticule in the scope. then check it against your known center point. if it is to close to the operator you can measure the error by moving your known centre, then machine that much off the 45 degree surface.
Or bin it and wait for MKII.

Stuart


*Though that's not to say I didn't. If the corner arrowed lines up with the back face of the mirror then I didn't, if it lines up with the front face then I did. I think lol....... working prototype remember

In the 3R box there was a orphan little angle marked Hensoldt Wetzlar. Turns out to be an edge locator. The angle has a fine line etched into a mirror backed disc of glass. The angle is placed over an edge and the scope's cross hairs are brought into alignment with the line indicating that the spindle centreline is on the edge. I'm pretty sure Hensoldt made the centring microscopes supplied as accessories by Deckel.

BT

I don't know anything about these gadgets.

Is this something similar ?

Center Scope (opitcal) | Other Tools & DIY | Gumtree Australia Mitcham Area - Blackwood | 1028773845

How would it work?

Rob

Hi BT,

Now that looks like a handy jigger.

Hi Rob,

I've never seen one with a chuck on it, but I guess it would save some swapping.
I can only assume it works pretty much the same way, though maybe aimed more at drills than mills. Getting your head close enough to a mill spindle could be a little painful. Also tang instead of draw bar. The optics would need to be more robust.

Certainly cheap enough, but how close it could get you I dont know. The Marcels are 20X and should be able to get within 0.0002". Now someone buy it before I do just to entertain myself lol

Stuart

Stu,

I had a bit of a fiddle on some paper seeing how an angled mount would go. Ignore the top scribble. The Marcel's barrel is 60mm in length. Practically, 60-ish mm from the mirror to the focusing point might be the attainable. Some increase would result from a decrease in the scope tube angle. I've drawn it at 30 degrees. I've drawn the mirror mounted in an Isoma fashion. I've conveniently glossed over the method of mounting the tube for the barrel. It would be screwed. Boring to ensure concentricity might be a challenge. I have worked out a way of mounting the barrel.
Another sketch.

BT


marcel 0.jpg

Hi BT,
Thats not a sketch, thats a work of art.

css.jpg


Now thats a sketch.

I think I may have a better idea(at least for those of us with Isomas).
ASSUMING the bore of the Isoma that holds the ocular/reticle assembly is parallel along its length and that funny cup thing is down towards the other end of the bore. Bin that thing I made. And make a adaptor like this. Job done.
If the Isoma bore isnt parallel you could make a few different lengths to cover the range of focal lengths you're after.
Then if you felt the need you could still make one "super short" scope with the Marcel, forget the silding scope and just go for the minium spindle to work piece distant you think you'll ever need. I'd think you might be able to squeeze 20mm. Surely even with your smallest direct mount collet and milling cutter it wouldnt need to be any less than that?

Now the adaptor may need to be modified if the bore diameter is to close to the diameter of the last lens in the ocular, but I'm guessing not.

Stuart

Stu, I've had enough nervous fiddling with the Isoma. I have no plan to delve inside the thing again. My focus is now on the Marcel. I do like the Isoma's simple mirror arrangement and I still have most of the 5 minute Araldite left. Keeping the mirror mount simple has merit. As we discussed previously, my plans to mount the mirror on a screw adjustable plate were excessive. The accidental dislodging of the Isoma's mirror has had an up side. When I fooled around with the Marcel in your prototype mount I was able to achieve focus 5mm from the mirror's lower edge. With the suggested sketched mounting a similar minimum distance could probably be achieved. Maximum would be around 50mm. The nosepiece needs protection. I was looking on Ebay last night for small screw on filters. My 50's Bolex 8mm movie camera has some bitty filters. If I can replicate the thread with my transposing gears, I reckon a haze or UV filter would do the trick. This is to me an interesting little project that if successful will greatly enhance the scope's useability. ( Sadly this post still lacks punctuation as a result of some computer glitch). BT

Wouldn't be any harder than the fist step of pulling the Marcel apart... but fair enough.

I think you'll find the Isomas mirror mount isn't as simple as it appears..... but it does have the up side of being easily replaced without having to bin the whole mount. Two grub screws to control the roll would be a good start. Now if you could come up with an easy way to control its "length" so the center line of the scope and spindle intersect on the surface off the mirror you're done. Other than that I think you'll just have to adjust length by trial and error machining.

Yes to the 5mm but your suggested sketch is 50mm high(plus as I'm pretty sure it will go fully up to the spindle as is). So that's 55mm+ minimum from the spindle to the work piece(not counting the dogs). The prototype is about 35mm minimum.

It really depends on just what you want the smallest spindle to work piece distance to be.


Stuart

Also as drawn the "mirror mount tube" maybe a little small in diameter.