So, I recently sold my gemolite, and my replacement microscope isn't completed so the darkfield is a bit sketchy. So when I saw a nice GIA diamond grader scope go by on eBay I figured it was a good time to try one out. I got it for just over 100 bucks including shipping. Here's the seller's picture:
I got it in, and overall I'd say it's a surprisingly really nice microscope, with good darkfield illumination. From what I can tell the base is basically an older Gemolite base, very similar to this original Gemolite (featuring an ancient B&L stereo head):
https://www.ebay.com/itm/B-L-GEM-Gemoli ... 3879743321 Instead of a Bausch and Lomb head it features a simple unbranded head with two magnfication settings, 1x and 3x, which you change between by rotating the barrel. This one was a little moldy, and it wasn't possible to easily reach each surface to clean them off, but honestly the image it produces is surprisingly good. It is marked 'Japan' on the bottom of the focus mount which narrows the possibilities. I kind of wonder if Olympus might have made it, since they used to do this kind of white labeling before they were a big name, but of course it could have been Kyowa or something too. You can get modern Chinese-made versions of this head wherever Chinese microscopes are sold, not that I'd recommend it. Anyway, while this head is OK it only goes up to 30x, and the small diameter of the head means that it can't easily be removed and swapped for a better stereo head. So the goal was to replace the old focus mount entirely with one more compatible with better microscope heads. In this case I happened to have an extra Stereozoom 7 and a basic Bausch and Lomb base, but this could be just as easily done with a standard 76mm holder that would take most other microscope heads. So, the first thing to do was see how the focus mount was held to the base. Unlike my gemolite V, where at one point I looked for and couldn't find access to any screws holding the focus mount on, access is very easy on the diamond grader, and the focus mount is just held on with two bolts, seen from below here:
Unscrewing them is easy--interestingly, the holes drilled through the base are 1/4 inch while the bolts are narrower (metric I assume), meaning that if they get at all loose there can be some wiggle, which I did experience on the scope out of the box. The focus arm also has four threaded holes even though only two were used, further evidence that this was a slapped-on replacement, presumably when the older B&L stereos (or maybe AO cycloptics, or whatever) were no longer available. The B&L focus mount has four screw holes, which of course are further apart and a different diameter:
Anyway, I went down to the Metal Supermarket and bought a nice thick 3/4 inch offcut of aluminum to make an adapter with, pictured here resting where the focus mount was:
It needs to accept two 1/4 inch bolts going down to attach to the base, and in this case four bolts going up to hold the B&L focus mount. In their indefinite wisdom B&L decided to use #8 36 bolts, ie the fine threaded ones that nobody uses, because apparently 32 threads for inch wasn't quite enough. I had to order some on eBay. The heads also all have to be recessed. Anyway, after some measuring and drilling the adapter looks like this:
Not completely perfect, but...
Here it is with the b&l bolts fitted:
I did have to shorten the bolts a bit to get them to fit, as the B&L focus arm doesn't have very deep threads, using my highly skilled 'hacksaw'n'file' technique.
aaaand I forgot to take a picture with the two larger bolts in. You have to put those bolts in, screw the b&l focus arm in, then fit the bolts to the base, then tighten a nut and washer onto each.
Here's the fit, and here...
...is the final fit! It works great from my early testing, very tight and the tilt works well.
Anyway, this is a long roundabout way of saying this is a nice base, and it isn't insanely hard or expensive to adapt a better head onto it. For the truly budget conscious and slightly handy drillpress owner it provides a decent alternative to buying an old gemolite V+ which don't too often go for under 500 on eBay.
Thanks! Now that gems are business I guess I needed a new hobby, and microscopes have grown to fill the niche. I always wanted to fiddle with things anyway, and now I can. Speaking of which, I made one other fix--the top and bottom of the microscope are held together by a single bolt which allows for the tilting feature. As it came, there was a little bit of horizontal play and the tilt had no resistance at all, so I unscrewed the bolt (just held on with a single nut) and added a nylon washer in the middle to tighten things. It is now just as I like it--no horizontal play at all and it moves smoothly but with a bit of resistance, and it can hold its angle now. A better fix would be to get two thinner nylon washers and put one on each side--as is there is probably some metal on metal rubbing which could cause problems eventually. I'll have to order some online. That time I'll remember to take pictures so the explanation makes more sense. Honestly, aside from being a bit smaller I'm not sure that there's anything lacking from it that you'd get from a Gemolite V.
I have created another monster. This one is on another diamond grader base, to which I have fitted a Nikon focus mount with an SMZ-1 head, a 3rd party 2x auxiliary lens (works quite well) and an LED ring light. Also added on a Bausch and Lomb overhead fluorescent light. Many of the diamond graders apparently shipped without the overhead lamp, though they still have a slot for it. The Bausch and Lomb table lamp unscrews from its base and screws right into the diamond grader (or gemolite V, VII, X) using the same screw. Anyway, it has a few different makers and paint colors represented, but darn if it isn't a nice scope!
This one was a bit more of a pain to fit because of the geometry of the focus arm, but in the end it came together very tightly and securely. The tilt mechanism has no trouble with the Nikon head--the older heads might have been smaller, but they were also very heavy.
Probably the wackiest yet. Using a Leica focus mount, a Nikon SMZ-1b head with an Olympus ergo spacer, B&L overhead fluorescent lamp and third party eyepieces and ring light. The original Gemolite/GemScope put the fluorescent overhead lamp on the focus mount, so there's no spot for one on the base. You could make one with a drill press but in this case I was able to mount it on the focus mount. One downside is that a lot of modern stereo focus mounts are very long, so the aluminum adapter has to extend backwards off the back of the scope to get the head centered over the illuminator well. Not a mechanical problem but it looks a bit goofy.
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