MJLorton Solar Power and Electronic Measurement Equipment Forum
General Category => General Discussion => Topic started by: SeanB on March 23, 2014, 07:29:55 AM
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I bought a Celestron USB microscope a while ago, and while it is usable, it is not a stellar performer, and has a very short focus distance. Cheap and with a pretty poor stand made from alloy and some movable joints that always fell over, and never kept position.
First try was to buy a cheap micrometer stand with a magnetic base, and used that as a base. Much improved, and a lot more rigid, but still was able to fall over and needed a ferrous surface to keep it stable.
Last week I went past the stone masons, and they had a skip outside with 30 tons of granite scrap in it. I stopped, and went looking for a small piece of stone to use. Found a nice 2.5kg piece of Rustenberg black granite there, mostly cut square and with about the right dimensions and nice and heavy. Took it back and washed it, then cleaned the one small lip of what would be the bottom and though how to attach the stand. Thought a while and looked at the existing stand, and that it used a plain M8 thread so i decided to make a hole with a matching M8 socket to hold it. Placed the clean block on the drill press and placed a 12mm masonry bit into the chuck, and started drilling, using water as a coolant to keep the drill cool. took about 3 minutes to drill 3cm into the block, and the drill needed a few applications of water to keep it cool, making a pile of grey mud with the excess water. Finished by cleaning it with water an scouring powder, then sanded it lightly all over and left it to dry.
(http://mjlorton.com/forum/index.php?action=dlattach;topic=585.0;attach=2673;image)
To make the mount I took an old broken brass pneumatic fitting, and removed the plastic parts for the press in side. Then tapped it to M8 and machined it down a little to fit, and took a little of the 1/8 NPT thread off as well to clean the dirt and thread sealer off. Mixed up some 5 minute clear epoxy and used it to hold the socket in the granite, using a M8 threaded rod in the drill press as a location and alignment jig.
Finished it off by painting with some polyurethane varnish to make it look good, was not going to polish it with grinding paste and rouge to do it naturally, so did the quick method. The cap screw there was used as a temp placeholder after an hour so I could get it out of the press, keeping the hole clear from the varnish.
Stuck some rubber textured belting on the bottom as well to protect the table. Back edge is unfinished, as I was not going to grind it off smooth with a diamond blade, plus it would have been very messy grinding in water. Chips in the edges are likely the reason it was thrown in the bin.
Cost to make it was nothing, as I had all the parts in stock, and did not have to buy the stone. Very firm mount now.
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Nice job! When drilling into granite blocks like this what are the chances of the block fracturing? Do you have a photo of the microscope mounted on the stand? :)
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Drilling is easy, you just have to use a masonry bit with a carbide insert, and do not use impact setting on the drill, just firm pressure and a lubricant and cooling. Water for both works very well, both cooling and removing the dust from the area as grit. Drilling all the way through means stopping when close to through and then drilling from the back side so the stone does not spall a stress cone when it is close to through. It is easy to break a thin section if it is not supported well directly under where you are drilling, preferably with a soft wooden scrap block so it will not suffer stress. Thick pieces are a lot easier, and if it is a half meter block you can use a hammer SDS drill and go through with a lot of noise and dust. Might be one drill bit per hole but then at that size you probably want to pay somebody to diamond drill it.
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Classic Sean...had to laugh when I read "a nice 2.5kg piece of Rustenberg black granit"!
A perfect stand...brilliant!
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Not a thing I would like to produce in bulk though, pretty heavy to ship, though this would probably survive the SAPO with little damage, though you will get some lost and some arriving broken into pieces. Eish Ungass!
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Nice! 8)