Centring Microscopes

[Anorak Bob]

Stu and I were fortunate to acquire Swiss Marcel Aubert centring scopes from a Thai Ebay seller for not a lot of money. I previously posted some photos showing the scope mounted at the end of an articulated arm which facilitated viewing work pieces, cutters etc. from a comfortable distance of about 90mm from the objective lens. Then Stuart asked me what was the largest direct fit ISO30 collet I had for the 13. I told him 12 and thought nothing more of it.

Two weeks latter a parcel arrived at the front door. Stu was the sender. The parcel contained a very neat, machined from billet, prototype adapter complete with 12mm:U arbor for the Marcel. The adapter has a mirror, a repurposed hard drive disc, set at 45 degrees and located on the arbor (spindle ) centreline. The body of the adapter is bored and features a split clamp.

Now here's the ingenious bit. The Marcel's generous focus distance can be used to great advantage. By moving the scope along the adapter's bore the focusing distance from the spindle nose can be altered. You might think big deal but it is. The 13 is frugal on Z. Having a scope that has a variable focal distance is a huge bonus when with a fixed length device, access is impossible. More about the latter later.

Here's the inventor's device.

287428

Thank you Stu.

BT

[Michael G]

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

Michael

[Oldneweng]

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

[Ueee]

A very neat holder Stu:2tsup:

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

[Anorak Bob]

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

287508

[Stustoys]

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


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

[Anorak Bob]

Easily rectified Stu.

287578

[Stustoys]

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 :D

[Anorak Bob]

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

[nearnexus]

I don't know anything about these gadgets.

Is this something similar ?

Center Scope (opitcal) | Other Tools & DIY | Gumtree Australia Mitcham Area - Blackwood | 1028773845 (http://www.gumtree.com.au/s-ad/blackwood/other-tools-diy/center-scope-opitcal-/1028773845)

How would it work?

Rob

[Stustoys]

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

[Anorak Bob]

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


287823

[Stustoys]

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

287955


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

[Anorak Bob]

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

[Stustoys]

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.

[Stustoys]

Hey you go BT,
The grey things are grub screws to hold the arbour/mirror holder in place. the depth of the mirror being adjusted by machining the face below.
The red circle is where a grub screw would be on each side. bearing on flats machined onto the arbor/mirror holder. this is for adjusting the rotation of the mirror.

I'm not exactly sure why I think this would be easier to make, though I'm pretty sure it would make lighting easier

Stuart

[Anorak Bob]

Hey you go BT,

The grey things are grub screws to hold the arbour/mirror holder in place. the depth of the mirror being adjusted by machining the face below...

Stuart

The machining to depth has me concerned. The mirror is affixed but could be covered during the turning but ensuring accurate realignment in the lathe of the arbor for turning could be tricky. And what happens if the mirror is too high? How about a finely threaded collar below the arbor flange for mirror height adjustment? Could well be whimsy on my behalf.:rolleyes:

BT

[Stustoys]

Hi BT,
The corner will be under cut so radial runout shouldnt be an issue. The theory is that the tight fit between the arbor and the bore well mean axial runout wont be a problem.( would guess the axil runout would be much less anyway... but I dont recall ever testing that).

To high with the mirror is a good thing, just machine more off the face. To low? bin the arbor and start again or make a shim spacer

I'm thinking you'd need the same sort of thing with the mirror holder from the side but holding it for machine could be a little tricky.

As with most of these thing, the second one will be easy lol

The threaded collar might be doable, but I think you'd have to give up some Z to make it fit.

Going to have to have a think about how big the mirror needs to be.


Stuart

[Stustoys]

Heres what you need BT ;)
Plus Stus cardboard and PVC pipe Marcel to Cannon adaptor.

Stuart

[Anorak Bob]

Those B and L Stereozoom scopes are a touch bulky. Half an hour of trawling through similar bulky looking stereo scopes and I found this restrained Zeiss delight. Sadly the seller wants too much for it. :no: The one eyed Marcel does provide some additional dexterity over the stereos.

Just so happens I have a hand me down, my wife's Canon Ixus, the same as yours. Both Bruce and Michael G sent me some black plastic bar a while back. After a bit of fiddling with some PVC pipe fiitings and some cardboard I'll have a go at an adapter using that bar.

BT

[Stustoys]

Make an offer Bob, you never know your luck. Looks nice, does it mention focal length?

I started with machiable wax but didnt like the result(which as it turns out machines pretty well even if you are running the lathe backwards lol). I have some "engineering plastic" of some sort but the last job I used it on it didnt seem all that stable on size over time. So layers of cardboard and Aquadhere it is. I think you'll be using the camera on 3X all the time so it wont really matter which on the steps on the lense you fit the tube to.

I guess I should take a picture of something with better finish that the kitchen rule.
Just remember not to turn the camera off before removing the adaptor.(though the cannon just errors, which is a good thing)

Stuart

[Anorak Bob]

Make an offer Bob, you never know your luck. Looks nice, does it mention focal length?

I started with machiable wax but didnt like the result(which as it turns out machines pretty well even if you are running the lathe backwards lol). I have some "engineering plastic" of some sort but the last job I used it on it didnt seem all that stable on size over time. So layers of cardboard and Aquadhere it is. I think you'll be using the camera on 3X all the time so it wont really matter which on the steps on the lense you fit the tube to.

I guess I should take a picture of something with better finish that the kitchen rule.
Just remember not to turn the camera off before removing the adaptor.(though the cannon just errors, which is a good thing)

Stuart

More info here Stu - Zeiss Stereo Microscope with Boom Stand | eBay (http://www.ebay.com/itm/Zeiss-Stereo-Microscope-with-Boom-Stand-/390679508326?pt=LH_DefaultDomain_0&hash=item5af6503566)

[Stustoys]

Wow its nice... but its not that nice.
Thanks

Stuart

[Anorak Bob]

Forget Carl, back to Marcel. Stu, I'm thinking now that your arbor ( or vertically ) mounted mirror is a better option than the mirror being mounted Isoma style. The latter squanders too much of the 92mm we have to play with. I've been scribbling on my drawing board trying to come up with a way of having an independent mirror mount that can be adjustable rather than it being integral with the arbor. The arbor could be hollow allowing a centring spigot to be machined on the mirror mount. I'll stop scribbling and draw what I'm trying to describe. BT ( still no functioning enter key on this keyboard, hence no punctuation ).

[azzrock]

hi guys yesterday i saw some deckel fp1 optical peace's
i think they were for edge finding.
is that the sort of thing as a centering microscope.
aaron

[Stustoys]

Hi Aaron,

I think some centring scopes only have one line, so I guess you could call them edge finders?
But I wouldnt really know as I've not layed hands on a real one.

Where's that drawing BT? (I've had yet another idea..... how about bringing the "Isoma mount" in from the opposite side to the scope? One bore straight through, so at least those two have to be in line)

Stuart

[Anorak Bob]

Hi Aaron,

I think some centring scopes only have one line, so I guess you could call them edge finders?
But I wouldnt really know as I've not layed hands on a real one.

Where's that drawing BT? (I've had yet another idea..... how about bringing the "Isoma mount" in from the opposite side to the scope? One bore straight through, so at least those two have to be in line)

Stuart

More scibbling at lunchtime today Stu.

I'm developing an idea for slight rotational adjustment of an Isoma-esque mount on the arbor centreline. Along the lines of notching the mount from both sides to form a rib and use opposing set screws acting against the rib to rotate and lock the mount. The tricky bit is axial adjustment. And an even trickier bit is how do we machine the end of the mirror mount at exactly 45 degrees?

BT

[Stustoys]

I'm not100% sure we arent talking about the same sort of adjustment
Given the small depth of field, I've been rethinking just how close we need to get. Infact i'm beginning to think you can use one error to correct another and it wont matter. Going to have to think a little more about that. The scope is sliding in a tube that is at a fixed angle to the mirror(assuming the nuffnuff machined the tube the right size). The focal length* is fixed. So the total error of the mirror angles is fixed reguardles of where in the tube the scope is........I think lol

Does epoxy stick to platinum?

Stuart

*different users may have different focal lengths so might need to adjust the scope if things were miles out.

[Anorak Bob]

I'm not100% sure we arent talking about the same sort of adjustment
Given the small depth of field, I've been rethinking just how close we need to get. Infact i'm beginning to think you can use one error to correct another and it wont matter. Going to have to think a little more about that. The scope is sliding in a tube that is at a fixed angle to the mirror(assuming the nuffnuff machined the tube the right size). The focal length* is fixed. So the total error of the mirror angles is fixed reguardles of where in the tube the scope is........I think lol

Does epoxy stick to platinum?

Stuart

*different users may have different focal lengths so might need to adjust the scope if things were miles out.

I will try to knock up a legible drawing tomorrow then we will see if we are discussing the same thing.

The epoxy can be used to form a clamp. When I re-adhered the Isoma mirror I avoided placing Araldite on the mirror face. I built it up the mirror sides and just over the back along the edges.

BT

[Michael G]

Rather than machine the angle exactly, how about making up a flap that is held back against a grub screw by a tension spring. To fine tune the angle, adjust the grubscrew. Loctite takes 24 hours to cure so you could assemble, adjust and then 24 hours later it should be fixed.

Michael

[Stustoys]

Well most of my post from late last night it a complete load, so best forget it.

Hi Michael,
Not that easy, at least the first attempt.... I found that out the hard way and it had me scratching my head for a day or so. Moving the mirror from one end like that changes the angle sure, but it also alters the distance of the mirror from the point the spindle and scope centrelines intersect. Which in my case meant that although I was moving the mirror by huge amounts the error stayed pretty much the same lol. Hope the sketch makes sense.
Having sketched that I'm thinking if the mirror was hinged from the other end, that might fix things?(at least for this error)

Such a simple little project :no:

Most of this wouldnt matter as much if the scope didnt slide.

Stuart

[Anorak Bob]

Something quick and rough. I think rotation about the arbor centreline might work via a pair of screws. Height adjustment is another thing. Mirror angle adjustment is something else. TF I have the Isoma.

290563

[Stustoys]

Hi BT,
Yeah, the notches and two grub screws is what I was getting at with this.

http://www.woodworkforums.com/attachments/f65/289700d1381926475-centring-microscopes-marcel-200.jpg

Though granted it helps that I know what I was trying to show ;)

Couple of other things, remember if you're going to go to the trouble of getting the 45deg spot on you have to get the 90deg spot on as well(though thats a little easier)

Have you worked out how you're going to make oval mirror?(though a large enough circle would do)

Having a tube for the Marcel is going to cost you Z.

Can you check the 92mm focal length? I measure mine at 72mm. Which is enough to force changes to the design. Not sure if its differences between the scopes or us.

Stuart

[Anorak Bob]

Stu,

Your mention of an oval mirror highlights another oversight on my behalf. The Isoma utilises a rectangular mirror but the Isoma has a short focal length. Marcel's objective lens is 15mm in diameter, far larger than the Isoma's. I need to check for vignetting, I'll take home a circle template. :)

Whilst perusing Deutsch Ebay early this morning I found this. Maybe an enticement for someone with more Z than I. Zentriermikroskop ISOMA ZP72 Swiss made Top Zustand | eBay (http://www.ebay.de/itm/Zentriermikroskop-ISOMA-ZP72-Swiss-made-Top-Zustand-/281193301381?pt=Messger%C3%A4te&hash=item41786d4585) BT