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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
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Anyone know where to buy semi-silvered glass?
Hi folks,
I just bought a metallurgical microscope. Unfortunately it has a problem: the semi-silvered mirror is missing. From the mirror's frame it looks to have been made from an oval piece of semi-silvered glass about 1/32" thick. I'm thinking I'm probably going to send the microscope back, but I just thought I'd ask here in case anyone can think of a source for a small piece of semi-silvered glass or plastic. Do I stand any chance of finding some? Best wishes, Chris |
#2
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Anyone know where to buy semi-silvered glass?
Christopher Tidy writes:
but I just thought I'd ask here in case anyone can think of a source for a small piece of semi-silvered glass or plastic. Inexpensive if you can find what you need: http://www.surplusshed.com http://www.anchoroptics.com/ Has what you need and charges accordingly: http://www.edmundoptics.com/ http://www.mellesgriot.com/ http://www.thorlabs.com/ http://www.newport.com/ |
#3
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Anyone know where to buy semi-silvered glass?
On Feb 21, 10:11 am, Christopher Tidy
wrote: Hi folks, I just bought a metallurgical microscope. Unfortunately it has a problem: the semi-silvered mirror is missing. From the mirror's frame it looks to have been made from an oval piece of semi-silvered glass about 1/32" thick. I'm thinking I'm probably going to send the microscope back, but I just thought I'd ask here in case anyone can think of a source for a small piece of semi-silvered glass or plastic. Do I stand any chance of finding some? Best wishes, Chris I have several long, narrow pieces from junk xerographic copy machines. I don't know what function they played. They probably would not help your situation. I think they are about 1/4 inch thick, 1/2 inch wide, on the silvered side, and probably 12 inches long. Paul |
#4
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Anyone know where to buy semi-silvered glass?
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#5
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Anyone know where to buy semi-silvered glass?
Richard J Kinch wrote:
Christopher Tidy writes: but I just thought I'd ask here in case anyone can think of a source for a small piece of semi-silvered glass or plastic. Inexpensive if you can find what you need: http://www.surplusshed.com http://www.anchoroptics.com/ Has what you need and charges accordingly: http://www.edmundoptics.com/ http://www.mellesgriot.com/ http://www.thorlabs.com/ http://www.newport.com/ Thanks for those links. I took the reflector frame out of the microscope today and measured it. Looks like the piece of glass needs to be 1" in diameter and 1/64" thick, though a thinner piece could possibly be used. According to some articles I've found online, certain metallurgical microscopes use a plain glass sheet which works by total internal reflection rather than a semi-silvered mirror. If that's the case with my microscope, it would make the glass much easier to find. I might even be able to use a circular glass cover slip. Then there's the problem of fitting the spring clip over such a thin piece of glass without breaking it. I figure I should order several pieces of glass! Best wishes, Chris |
#6
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Anyone know where to buy semi-silvered glass?
On 2008-02-23, Christopher Tidy wrote:
[ ... ] Thanks for those links. I took the reflector frame out of the microscope today and measured it. Looks like the piece of glass needs to be 1" in diameter and 1/64" thick, though a thinner piece could possibly be used. According to some articles I've found online, certain metallurgical microscopes use a plain glass sheet which works by total internal reflection rather than a semi-silvered mirror. If that's the case with my microscope, it would make the glass much easier to find. I might even be able to use a circular glass cover slip. The modern way of making semi-silvered mirrors is by vacuum evaporation. You need a really good vacuum pump, some large diameter stainless steel plumbing with flange couplings and knife-edges which bite into copper washers -- replace the washer after every use. Once you pump down to a low enough vacuum (the roughing pump gets you most of the way, then you go to something like a "sorbtion" pump or a turbo pump, or oil diffusion pump), then you put high current through a filament around which is wrapped the metal which you wish to deposit -- like perhaps aluminum wire. This boils off the metal, and deposits it on the glass. You can control the thickness (and thus the opaqueness) by timing, or the better way is with a crystal oscillator, with one side of the crystal exposed adjacent to the glass being coated. You can determine how thick the coating is by the change in frequency of the oscillator from zeroing it before you start the plating. Obviously -- this is a lot of stuff to do at home -- but you may be able to find someone who retired from doing such work and is continuing to play with it at home. I don't know where you live, but it could be a possible choice. Hmm ... if you are near someplace with a college which does Scientific work, you might be able to find someone there to help you. Obviously -- cut the glass to shape *first*, and then coat it. The real trick is coming up with a way to hold it down during plating without blocking more than a bare minimum of the area -- say three tiny fingers just barely sticking over the edge. And the whole fixture should be metal, no plastics in the high vacuum. Good Luck, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#7
Posted to rec.crafts.metalworking
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Anyone know where to buy semi-silvered glass?
Christopher Tidy writes:
According to some articles I've found online, certain metallurgical microscopes use a plain glass sheet which works by total internal reflection rather than a semi-silvered mirror. If that's the case with my microscope, it would make the glass much easier to find. I might even be able to use a circular glass cover slip. Or even try cutting some 0.015 Mylar sheet (overhead transparencies) with scissors. Not really optically flat, but maybe worth experimenting with. |
#8
Posted to rec.crafts.metalworking
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Anyone know where to buy semi-silvered glass?
Richard J Kinch wrote:
Christopher Tidy writes: According to some articles I've found online, certain metallurgical microscopes use a plain glass sheet which works by total internal reflection rather than a semi-silvered mirror. If that's the case with my microscope, it would make the glass much easier to find. I might even be able to use a circular glass cover slip. Or even try cutting some 0.015 Mylar sheet (overhead transparencies) with scissors. Not really optically flat, but maybe worth experimenting with. Might not be what your looking for but take a look at some of the replacement side mirror items at your local parts store. The Help mirror I just bought is a strange item. You can hold it to a light source and see through it, Put it against a backer material and it becomes a good mirror. It was a simple rectangular mirror for replacing the older style GM truck mirrors. Thickness wise it is maybe an 1/8" -- Steve W. Near Cooperstown, New York |
#9
Posted to rec.crafts.metalworking
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Anyone know where to buy semi-silvered glass?
Christopher Tidy wrote:
... I'm probably going to send the microscope back, ... Maybe they can send you the replacement mirror. Bob |
#10
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Anyone know where to buy semi-silvered glass?
Bob Engelhardt wrote:
Christopher Tidy wrote: ... I'm probably going to send the microscope back, ... Maybe they can send you the replacement mirror. Bob I don't know. They're a used tools dealership, so I have my doubts. I think I'll either get a return or a discount, but I doubt I'll get a new mirror. Best wishes, Chris |
#11
Posted to rec.crafts.metalworking
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Anyone know where to buy semi-silvered glass?
DoN. Nichols wrote:
On 2008-02-23, Christopher Tidy wrote: [ ... ] Thanks for those links. I took the reflector frame out of the microscope today and measured it. Looks like the piece of glass needs to be 1" in diameter and 1/64" thick, though a thinner piece could possibly be used. According to some articles I've found online, certain metallurgical microscopes use a plain glass sheet which works by total internal reflection rather than a semi-silvered mirror. If that's the case with my microscope, it would make the glass much easier to find. I might even be able to use a circular glass cover slip. The modern way of making semi-silvered mirrors is by vacuum evaporation. You need a really good vacuum pump, some large diameter stainless steel plumbing with flange couplings and knife-edges which bite into copper washers -- replace the washer after every use. Once you pump down to a low enough vacuum (the roughing pump gets you most of the way, then you go to something like a "sorbtion" pump or a turbo pump, or oil diffusion pump), then you put high current through a filament around which is wrapped the metal which you wish to deposit -- like perhaps aluminum wire. This boils off the metal, and deposits it on the glass. You can control the thickness (and thus the opaqueness) by timing, or the better way is with a crystal oscillator, with one side of the crystal exposed adjacent to the glass being coated. You can determine how thick the coating is by the change in frequency of the oscillator from zeroing it before you start the plating. Obviously -- this is a lot of stuff to do at home -- but you may be able to find someone who retired from doing such work and is continuing to play with it at home. I don't know where you live, but it could be a possible choice. Hmm ... if you are near someplace with a college which does Scientific work, you might be able to find someone there to help you. Obviously -- cut the glass to shape *first*, and then coat it. The real trick is coming up with a way to hold it down during plating without blocking more than a bare minimum of the area -- say three tiny fingers just barely sticking over the edge. And the whole fixture should be metal, no plastics in the high vacuum. Thanks. That was a fascinating read. I have a small two-stage mechanical vacuum pump. I was also offered an oil diffusion pump a while back, and I suspect the offer is still open. But it does seem a great deal of work when I hadn't intended the microscope to be a project in itself! Best wishes, Chris |
#12
Posted to rec.crafts.metalworking
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Anyone know where to buy semi-silvered glass?
Richard J Kinch wrote:
Christopher Tidy writes: According to some articles I've found online, certain metallurgical microscopes use a plain glass sheet which works by total internal reflection rather than a semi-silvered mirror. If that's the case with my microscope, it would make the glass much easier to find. I might even be able to use a circular glass cover slip. Or even try cutting some 0.015 Mylar sheet (overhead transparencies) with scissors. Not really optically flat, but maybe worth experimenting with. I had wondered about this, but like you I was concerned about the flexibility of the sheet. It might not matter, as the sheet only reflects the illuminating light, not the image, but I'd prefer to do a good job. Best wishes, Chris |
#13
Posted to rec.crafts.metalworking
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Anyone know where to buy semi-silvered glass?
Steve W. wrote:
Richard J Kinch wrote: Christopher Tidy writes: According to some articles I've found online, certain metallurgical microscopes use a plain glass sheet which works by total internal reflection rather than a semi-silvered mirror. If that's the case with my microscope, it would make the glass much easier to find. I might even be able to use a circular glass cover slip. Or even try cutting some 0.015 Mylar sheet (overhead transparencies) with scissors. Not really optically flat, but maybe worth experimenting with. Might not be what your looking for but take a look at some of the replacement side mirror items at your local parts store. The Help mirror I just bought is a strange item. You can hold it to a light source and see through it, Put it against a backer material and it becomes a good mirror. It was a simple rectangular mirror for replacing the older style GM truck mirrors. Thickness wise it is maybe an 1/8" That reminds me. CD-Rs look semi-silvered in bright light, don't they? But I suspect they're a bit too opaque. Best wishes, Chris |
#14
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Anyone know where to buy semi-silvered glass?
How about a reflective ND filter?
Edmond Scientific has them. I think I might have some laying around. Send me an email at t miller @ u maryland . edu. (remove the spaces) Tom "Christopher Tidy" wrote in message ... Hi folks, I just bought a metallurgical microscope. Unfortunately it has a problem: the semi-silvered mirror is missing. From the mirror's frame it looks to have been made from an oval piece of semi-silvered glass about 1/32" thick. I'm thinking I'm probably going to send the microscope back, but I just thought I'd ask here in case anyone can think of a source for a small piece of semi-silvered glass or plastic. Do I stand any chance of finding some? Best wishes, Chris |
#15
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Anyone know where to buy semi-silvered glass?
Tom M wrote:
How about a reflective ND filter? Edmond Scientific has them. I think I might have some laying around. Send me an email at t miller @ u maryland . edu. (remove the spaces) I don't think an ND filter will work. The reflector needs to reflect the light in a consistent direction, whereas the ND filter will disperse the light randomly, I believe. Thanks for the suggestion though! Best wishes, Chris |
#16
Posted to rec.crafts.metalworking
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Anyone know where to buy semi-silvered glass?
On Sat, 23 Feb 2008 22:56:28 +0000, Christopher Tidy
wrote: Thanks for those links. I took the reflector frame out of the microscope today and measured it. Looks like the piece of glass needs to be 1" in diameter and 1/64" thick, though a thinner piece could possibly be used. According to some articles I've found online, certain metallurgical microscopes use a plain glass sheet which works by total internal reflection rather than a semi-silvered mirror. If that's the case with my microscope, it would make the glass much easier to find. I might even be able to use a circular glass cover slip. Then there's the problem of fitting the spring clip over such a thin piece of glass without breaking it. I figure I should order several pieces of glass! Best wishes, Chris Make up some Tollens reagent (ammoniacal silver nitrate) and use a bit of glucose solution to set it off. £50 minimum order worth of chemicals from www.lpchemicals.com Mark Rand RTFM |
#17
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Anyone know where to buy semi-silvered glass?
Mark Rand wrote:
On Sat, 23 Feb 2008 22:56:28 +0000, Christopher Tidy wrote: Thanks for those links. I took the reflector frame out of the microscope today and measured it. Looks like the piece of glass needs to be 1" in diameter and 1/64" thick, though a thinner piece could possibly be used. According to some articles I've found online, certain metallurgical microscopes use a plain glass sheet which works by total internal reflection rather than a semi-silvered mirror. If that's the case with my microscope, it would make the glass much easier to find. I might even be able to use a circular glass cover slip. Then there's the problem of fitting the spring clip over such a thin piece of glass without breaking it. I figure I should order several pieces of glass! Best wishes, Chris Make up some Tollens reagent (ammoniacal silver nitrate) and use a bit of glucose solution to set it off. £50 minimum order worth of chemicals from www.lpchemicals.com I'm not too keen on this idea. I'm wanting a working microscope rather than a time-consuming project. Best wishes, Chris |
#18
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Anyone know where to buy semi-silvered glass?
On 2008-02-24, Christopher Tidy wrote:
DoN. Nichols wrote: [ ... ] Thanks. That was a fascinating read. I have a small two-stage mechanical vacuum pump. I was also offered an oil diffusion pump a while back, and I suspect the offer is still open. But it does seem a great deal of work when I hadn't intended the microscope to be a project in itself! I can understand that -- but I figured that you should know what is actually involved so you could decide for yourself. Since there was a lot of this being done in an Army R&D lab where I used to work, I got to learn how it was done, although I never did it myself. But I always like to learn how anything is done, so I kept my eyes open. For that matter -- the older copies of The CRC _Handbook of Chemistry and Physics_ used to have a lab tricks section which included two or three ways to silver mirrors. Those were mostly chemical approaches, not high vacuum deposition. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#19
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Anyone know where to buy semi-silvered glass?
Christopher Tidy wrote:
Mark Rand wrote: On Sat, 23 Feb 2008 22:56:28 +0000, Christopher Tidy wrote: Thanks for those links. I took the reflector frame out of the microscope today and measured it. Looks like the piece of glass needs to be 1" in diameter and 1/64" thick, though a thinner piece could possibly be used. Just ask yer dentist for one of those disposable inspection mirrors. Remove the mirror from the plastic housing/handle. Insert in microscope holder. Done. technomaNge -- Please visit http://www.anysoldier.com and make a donation. |
#20
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Anyone know where to buy semi-silvered glass?
technomaNge wrote:
Christopher Tidy wrote: Mark Rand wrote: On Sat, 23 Feb 2008 22:56:28 +0000, Christopher Tidy wrote: Thanks for those links. I took the reflector frame out of the microscope today and measured it. Looks like the piece of glass needs to be 1" in diameter and 1/64" thick, though a thinner piece could possibly be used. Just ask yer dentist for one of those disposable inspection mirrors. Remove the mirror from the plastic housing/handle. Insert in microscope holder. Done. Are they semi-silvered? Many thanks, Chris |
#21
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Anyone know where to buy semi-silvered glass?
Charlie+ wrote:
On Thu, 21 Feb 2008 10:11:57 -0800 (PST), Christopher Tidy wrote as underneath my scribble : I had a microscope with a ~45 deg semisilvered mirror that needed replacement, tried a standard mirror but turned out it was a "cold mirror" and removed IR from the lightpath to save IR from the users eyes (multicoated so IR passes straight through). Be good idea to find out the original specification....!? C+ The best that will be possible is to look at an original reflector. To the best of my knowledge, W. Watson & Sons are no longer in business. Best wishes, Chris |
#22
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Anyone know where to buy semi-silvered glass?
DoN. Nichols wrote:
On 2008-02-24, Christopher Tidy wrote: DoN. Nichols wrote: [ ... ] Thanks. That was a fascinating read. I have a small two-stage mechanical vacuum pump. I was also offered an oil diffusion pump a while back, and I suspect the offer is still open. But it does seem a great deal of work when I hadn't intended the microscope to be a project in itself! I can understand that -- but I figured that you should know what is actually involved so you could decide for yourself. Since there was a lot of this being done in an Army R&D lab where I used to work, I got to learn how it was done, although I never did it myself. But I always like to learn how anything is done, so I kept my eyes open. For that matter -- the older copies of The CRC _Handbook of Chemistry and Physics_ used to have a lab tricks section which included two or three ways to silver mirrors. Those were mostly chemical approaches, not high vacuum deposition. Thanks very much for explaining it to me. I too like to learn how things are made. But sometime I feel the need to limit the number of projects I'm working on! Best wishes, Chris |
#23
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Anyone know where to buy semi-silvered glass?
On 2008-02-25, technomaNge wrote:
Christopher Tidy wrote: Mark Rand wrote: On Sat, 23 Feb 2008 22:56:28 +0000, Christopher Tidy wrote: Thanks for those links. I took the reflector frame out of the microscope today and measured it. Looks like the piece of glass needs to be 1" in diameter and 1/64" thick, though a thinner piece could possibly be used. Just ask yer dentist for one of those disposable inspection mirrors. Remove the mirror from the plastic housing/handle. Insert in microscope holder. Done. I suspect that it won't work for him. What he needs is a semi-silvered mirror -- something like 50-75% of the light passes through, and the rest bounces. It goes between the eyepiece and the objective lens set up so light from a lamp to the side bounces down and passes through the objective lens to illuminate the object under study, and the image which comes back has most of the light going on up to the eyepiece, with the smaller percentage bounced back to the light, where it does nothing useful. What would be even better would be an arrangement where all of the light from the lamp goes through the lens, and all which bounces back from the object under study goes up to the eyepiece, but physics is not quite so cooperative. Enjoy, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#24
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Anyone know where to buy semi-silvered glass?
DoN. Nichols wrote:
On 2008-02-25, technomaNge wrote: Christopher Tidy wrote: Mark Rand wrote: On Sat, 23 Feb 2008 22:56:28 +0000, Christopher Tidy wrote: Thanks for those links. I took the reflector frame out of the microscope today and measured it. Looks like the piece of glass needs to be 1" in diameter and 1/64" thick, though a thinner piece could possibly be used. Just ask yer dentist for one of those disposable inspection mirrors. Remove the mirror from the plastic housing/handle. Insert in microscope holder. Done. I suspect that it won't work for him. What he needs is a semi-silvered mirror -- something like 50-75% of the light passes through, and the rest bounces. It goes between the eyepiece and the objective lens set up so light from a lamp to the side bounces down and passes through the objective lens to illuminate the object under study, and the image which comes back has most of the light going on up to the eyepiece, with the smaller percentage bounced back to the light, where it does nothing useful. What would be even better would be an arrangement where all of the light from the lamp goes through the lens, and all which bounces back from the object under study goes up to the eyepiece, but physics is not quite so cooperative. Thinking about it quickly, I think the efficiency might be better using a plain sheet of glass and making use of the total internal reflection effect. What do you think? Best wishes, Chris |
#25
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Anyone know where to buy semi-silvered glass?
On 2008-02-26, Christopher Tidy wrote:
DoN. Nichols wrote: On 2008-02-25, technomaNge wrote: [ ... ] Just ask yer dentist for one of those disposable inspection mirrors. Remove the mirror from the plastic housing/handle. Insert in microscope holder. Done. I suspect that it won't work for him. What he needs is a semi-silvered mirror -- something like 50-75% of the light passes [ ... ] Thinking about it quickly, I think the efficiency might be better using a plain sheet of glass and making use of the total internal reflection effect. What do you think? Hmm ... at what angle do you get total internal reflection? IIRC it is a function of the index of refraction. And while binocular prisms get TIR at 45 degrees, the light enters and exits at close to 90 degrees, thanks to the design of the prism. If you have the light entering at 45 degrees on one face, it will be bent towards the other face so the angle will be steeper than 45 degrees. And -- *if* you got TIR with the glass (say you made a full 45-45-90 prism to get the entrance angles right) you would get nothing through to your eyepiece. So I think that the semi-silvered is the better choice. Hmm ... the light is not focused where it passes through the mirror, so you might be able to take a first-surface mirror and scribe through the silvering in a pattern to get something like 30-45% reflection, and then you might be able to use it. I've seen scribed patterns in mirrors in SLR cameras, with the CDS cell for metering behind the scribed section. Enjoy, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#26
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Anyone know where to buy semi-silvered glass?
"Christopher Tidy" wrote in message ... Tom M wrote: How about a reflective ND filter? Edmond Scientific has them. I think I might have some laying around. Send me an email at t miller @ u maryland . edu. (remove the spaces) I don't think an ND filter will work. The reflector needs to reflect the light in a consistent direction, whereas the ND filter will disperse the light randomly, I believe. Thanks for the suggestion though! Best wishes, Chris No, these are semi-reflective. They are not absorptive. If you contact me via email, I will send you a picture. I'll send you one for nothing if it will work. They are 0.060 thick and 50 x 50 mm square. Tom |
#27
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Anyone know where to buy semi-silvered glass?
"Tom M" wrote in message . .. "Christopher Tidy" wrote in message ... Tom M wrote: How about a reflective ND filter? Edmond Scientific has them. I think I might have some laying around. Send me an email at t miller @ u maryland . edu. (remove the spaces) I don't think an ND filter will work. The reflector needs to reflect the light in a consistent direction, whereas the ND filter will disperse the light randomly, I believe. Thanks for the suggestion though! Best wishes, Chris No, these are semi-reflective. They are not absorptive. If you contact me via email, I will send you a picture. I'll send you one for nothing if it will work. They are 0.060 thick and 50 x 50 mm square. Tom how about silver coated dichroic glass? i'd bet http://www.cbs-dichroic.com/main.asp could make you a bunch. i have a contact who does a lot of glass grinding for precision optics companies who also might be able to provide this. contact me at chaniarts at yahoo dot com if you want a reference. regards, charlie http://glassartists.com/chaniarts |
#28
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Anyone know where to buy semi-silvered glass?
DoN. Nichols wrote:
snip Hmm ... at what angle do you get total internal reflection? IIRC it is a function of the index of refraction. And while binocular prisms get TIR at 45 degrees, the light enters and exits at close to 90 degrees, thanks to the design of the prism. If you have the light entering at 45 degrees on one face, it will be bent towards the other face so the angle will be steeper than 45 degrees. And -- *if* you got TIR with the glass (say you made a full 45-45-90 prism to get the entrance angles right) you would get nothing through to your eyepiece. So I think that the semi-silvered is the better choice. Hmm ... the light is not focused where it passes through the mirror, so you might be able to take a first-surface mirror and scribe through the silvering in a pattern to get something like 30-45% reflection, and then you might be able to use it. I've seen scribed patterns in mirrors in SLR cameras, with the CDS cell for metering behind the scribed section. 41.8 degrees for light travelling from glass into air. This would mean that the mirror would need to be at an angle of less than 41.8 degrees to the horizontal. The only disadvantage as far as I can see is that if the light emerging from the lamphouse is horizontal, it won't be travelling quite vertically downwards after being reflected. But you could correct this by tilting the lamphouse and its lenses down slightly. Best wishes, Chris |
#29
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Anyone know where to buy semi-silvered glass?
Tom M wrote:
snip No, these are semi-reflective. They are not absorptive. If you contact me via email, I will send you a picture. I'll send you one for nothing if it will work. They are 0.060 thick and 50 x 50 mm square. Thanks for the offer, but I discovered that the design is intended to use plain glass. I called a few glass suppliers and couldn't find a piece the right size. In the end I found another identical microscope on eBay cheap. It has a few issues but with the pair I'm sure I can build a working microscope. Nevertheless, thanks very much for the offer. Best wishes, Chris |
#30
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Anyone know where to buy semi-silvered glass?
charlie wrote:
"Tom M" wrote in message . .. "Christopher Tidy" wrote in message ... Tom M wrote: How about a reflective ND filter? Edmond Scientific has them. I think I might have some laying around. Send me an email at t miller @ u maryland . edu. (remove the spaces) I don't think an ND filter will work. The reflector needs to reflect the light in a consistent direction, whereas the ND filter will disperse the light randomly, I believe. Thanks for the suggestion though! Best wishes, Chris No, these are semi-reflective. They are not absorptive. If you contact me via email, I will send you a picture. I'll send you one for nothing if it will work. They are 0.060 thick and 50 x 50 mm square. Tom how about silver coated dichroic glass? i'd bet http://www.cbs-dichroic.com/main.asp could make you a bunch. i have a contact who does a lot of glass grinding for precision optics companies who also might be able to provide this. contact me at chaniarts at yahoo dot com if you want a reference. Surely that wouldn't work, because you need to reflect and transmit the same wavelengths of light in the microscope? Best wishes, Chris |
#31
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Anyone know where to buy semi-silvered glass?
In the end I tracked down another Watson "Standard Metallurgical"
microscope on eBay. It's in better condition, but still has a few issues. With spare parts from the first I should now be able to build a microscope in good working order. For the benefit of anyone who comes across this thread in the future, the reflector in the Watson "Standard Metallurgical" is plain glass, not a semi-silvered mirror. Many thanks, Chris |
#32
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Anyone know where to buy semi-silvered glass?
DoN. Nichols wrote:
snip Hmm ... at what angle do you get total internal reflection? IIRC it is a function of the index of refraction. And while binocular prisms get TIR at 45 degrees, the light enters and exits at close to 90 degrees, thanks to the design of the prism. If you have the light entering at 45 degrees on one face, it will be bent towards the other face so the angle will be steeper than 45 degrees. And -- *if* you got TIR with the glass (say you made a full 45-45-90 prism to get the entrance angles right) you would get nothing through to your eyepiece. So I think that the semi-silvered is the better choice. Hmm ... the light is not focused where it passes through the mirror, so you might be able to take a first-surface mirror and scribe through the silvering in a pattern to get something like 30-45% reflection, and then you might be able to use it. I've seen scribed patterns in mirrors in SLR cameras, with the CDS cell for metering behind the scribed section. A scribed mirror is a fascinating idea! But it seems like it is done by total internal reflection in this microscope. I've yet to completely absorb the intricacies of the optical system, but it's interesting to note that the reflector pivot is not directly above the centre of the objective lens. It's slightly in front on the lens, i.e., closer to the light source. I also need some lens-removing tools. Not sure what they're called. I'll probably post a message about those at r.c.m in the next few days. Thanks for the help. Best wishes, Chris |
#33
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Anyone know where to buy semi-silvered glass?
On 2008-03-05, Christopher Tidy wrote:
DoN. Nichols wrote: [ ... ] Hmm ... the light is not focused where it passes through the mirror, so you might be able to take a first-surface mirror and scribe through the silvering in a pattern to get something like 30-45% reflection, and then you might be able to use it. I've seen scribed patterns in mirrors in SLR cameras, with the CDS cell for metering behind the scribed section. A scribed mirror is a fascinating idea! But it seems like it is done by total internal reflection in this microscope. I've yet to completely absorb the intricacies of the optical system, but it's interesting to note that the reflector pivot is not directly above the centre of the objective lens. It's slightly in front on the lens, i.e., closer to the light source. O.K. I also need some lens-removing tools. Not sure what they're called. I'll probably post a message about those at r.c.m in the next few days. Which format? The ones to access two slots on opposite sides of a retaining ring? Those are what would be called a spanner wrench here (actually -- "ring spanner") in the US -- unlike the UK where I believe the term to match what I would call an "open end wrench". The ones which I have are sets of arms which slide along a bar and are locked to the bar at the proper distance, and which mount either pins or slot drivers of appropriate size to match the slots or pin holes. If you need it, I can photograph my set for an example of a pretty good set. I also used to have a set from Edmund Scientific which used some hex steel shaft to hold the arms, with slots milled in them to allow the arms to cross at a slight angle to the expected right angle. In the ends of the arms is a hex socket with a setscrew (grub screw?) to hold them in, and then a pin or slot driver machined on the end. These were not nearly as rigid, but were quite affordable at the time. I used them both for camera lenses and for wris****ch back removal/replacement. O.K. Edmund no longer carries anything of the sort, but I have found an example made in India to the same design. Just better packaging as it is in a hinged wooden case instead of a cardboard box. I have not found a price, but perhaps you can with more searching. Sorry about the extra-long URL http://anuuj.trustpass.alibaba.com/product/12241451/Spanner_Wrench_Lens_Opening_Tool_Tools_Adjustable. html Let me break the URL into sections for individual cut-and-paste if your system does not honor the '' and '' to keep it together: http://anuuj.trustpass.alibaba.com/product/12241451/ Spanner_Wrench_Lens_Opening_Tool_Tools_Adjustable. html Or do you mean those to grip the knurled ring on the typical microscope objective lens? Those *should* be loose enough so finger grip should be sufficient to unscrew them. There are hinged versions of the spanners which are sold to remove the screw-on backs of "waterproof" watches. There is typically a knurled wheel in the middle of a double-threaded screw (LH on one side, RH on the other) between the arms to adjust the spacing with sufficient precision. Enjoy, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#34
Posted to rec.crafts.metalworking
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Anyone know where to buy semi-silvered glass?
Christopher Tidy writes:
I also need some lens-removing tools. Not sure what they're called. You must mean spanners. Edmund Optics, Thorlabs for some pricey ones. Ebay for a budget type. Often the rings are hardly tight, and can be turned out with the tip of a tiny screwdriver on one side, or the filed-down tips of needlenose pliers on both sides. Give it a try. |
#35
Posted to rec.crafts.metalworking
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Anyone know where to buy semi-silvered glass?
snip Which format? The ones to access two slots on opposite sides of a retaining ring? Those are what would be called a spanner wrench here (actually -- "ring spanner") in the US -- unlike the UK where I believe the term to match what I would call an "open end wrench". The ones which I have are sets of arms which slide along a bar and are locked to the bar at the proper distance, and which mount either pins or slot drivers of appropriate size to match the slots or pin holes. I actually need both. Most urgently I need the kind which fits into two slots diametrically opposite each other in the threaded ring. The slots appear to be square in cross section. I could also do with having one which fits into a pair of round holes, too. Like the kind used for "spanner head" screws. But this tool must be like a screwdriver, as it has to go down the tube of the microscope for removing the nosepiece. If you need it, I can photograph my set for an example of a pretty good set. If they're no longer available, don't worry. The maker's name might be useful so I can search on eBay, though. I also used to have a set from Edmund Scientific which used some hex steel shaft to hold the arms, with slots milled in them to allow the arms to cross at a slight angle to the expected right angle. In the ends of the arms is a hex socket with a setscrew (grub screw?) to hold them in, and then a pin or slot driver machined on the end. These were not nearly as rigid, but were quite affordable at the time. I used them both for camera lenses and for wris****ch back removal/replacement. Do you know what the official name for the set is? O.K. Edmund no longer carries anything of the sort, but I have found an example made in India to the same design. Just better packaging as it is in a hinged wooden case instead of a cardboard box. I have not found a price, but perhaps you can with more searching. Sorry about the extra-long URL http://anuuj.trustpass.alibaba.com/product/12241451/Spanner_Wrench_Lens_Opening_Tool_Tools_Adjustable. html Let me break the URL into sections for individual cut-and-paste if your system does not honor the '' and '' to keep it together: http://anuuj.trustpass.alibaba.com/product/12241451/ Spanner_Wrench_Lens_Opening_Tool_Tools_Adjustable. html Unfortunately I can't tell from that picture which tips are included. It's also too big for my second application. By the way, this is a ring spanner in the UK: http://www.britishfasteners.com/mm5/...00003/er14.jpg Many thanks, Chris |
#36
Posted to rec.crafts.metalworking
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Anyone know where to buy semi-silvered glass?
Richard J Kinch wrote:
Christopher Tidy writes: I also need some lens-removing tools. Not sure what they're called. You must mean spanners. Edmund Optics, Thorlabs for some pricey ones. Ebay for a budget type. What's the official name for these spanners? Often the rings are hardly tight, and can be turned out with the tip of a tiny screwdriver on one side, or the filed-down tips of needlenose pliers on both sides. Give it a try. I'm reluctant to try it. I don't want to cause any damage. Many thanks, Chris |
#37
Posted to rec.crafts.metalworking
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Anyone know where to buy semi-silvered glass?
Christopher Tidy writes:
What's the official name for these spanners? Spanner wrench or adjustable spanner wrench. The first fixed type is a thin hollow tube with tiny projections on the end to fit the holes or slots in the retaining ring. This is better at deeply recessed locations. The second is the adjustable gadget with interchangeable tips. See: http://www.thorlabs.com/advSearch.cfm and search for "spanner". See: http://www.edmundoptics.com/ and search likewise. I'm reluctant to try it. I don't want to cause any damage. Really, just nudge it with a jeweler's screwdriver or dental pick and see if it doesn't back right out. |
#38
Posted to rec.crafts.metalworking
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Anyone know where to buy semi-silvered glass?
On 2008-03-07, Christopher Tidy wrote:
snip Which format? The ones to access two slots on opposite sides of a retaining ring? Those are what would be called a spanner wrench here (actually -- "ring spanner") in the US -- unlike the UK where I believe the term to match what I would call an "open end wrench". The ones which I have are sets of arms which slide along a bar and are locked to the bar at the proper distance, and which mount either pins or slot drivers of appropriate size to match the slots or pin holes. I actually need both. Most urgently I need the kind which fits into two slots diametrically opposite each other in the threaded ring. The slots appear to be square in cross section. Typically -- most sets can handle both depending on the tips installed. I could also do with having one which fits into a pair of round holes, too. Like the kind used for "spanner head" screws. But this tool must be like a screwdriver, as it has to go down the tube of the microscope for removing the nosepiece. If you need it, I can photograph my set for an example of a pretty good set. If they're no longer available, don't worry. The maker's name might be useful so I can search on eBay, though. I have no idea who made them, as I never saw the original box. All parts have the numbers stamped on them. 49A17795-1 is the shortest bar 49A17795-2 is the middle length bar 49A17795-3 is the longest bar 49B17788-R is the right-hand joining bracket 49B17788-L is the left-hand joining bracket 49B17790-R is the right-hand upright tip holder 49B17790-L is the left-hand upright tip holder Into one end of each of the above is a double-ended pin with the tip turned to 0.061" diameter on one end, and to 0.031" on the other. Others probably existed, but these are all that I have until I need to make more of my own. (As a matter of fact, this is the first time that I knew that it was double-ended, since I have never needed to change it. The OD of the pin body is 0.125" (1/8") The other end of the holder accepts the following tips. 49A17791-1-R is the right-hand tip for thin screwdriver slots (0.043") 49A17791-1-L is the left-hand tip for thin screwdriver slots 49A17791-2-R is the right-hand tip for medium screwdriver slots (0.062") 49A17791-2-L is the left-hand tip for medium screwdriver slots 49A17791-3-R is the right-hand tip for wide screwdriver slots (0.091") 49A17791-3-L is the left-hand tip for wide screwdriver slots All of the screwdriver tips look like somewhat this: +-+ | | | | \ / V with the 'V' point towards the outside. The arms for this are at right angles to the beam, but have an offset so they can be set up for something with a small ID or a large ID. I also used to have a set from Edmund Scientific which used some hex steel shaft to hold the arms, with slots milled in them to allow the arms to cross at a slight angle to the expected right angle. In the ends of the arms is a hex socket with a setscrew (grub screw?) to hold them in, and then a pin or slot driver machined on the end. These were not nearly as rigid, but were quite affordable at the time. I used them both for camera lenses and for wris****ch back removal/replacement. Do you know what the official name for the set is? Since Edumund no longer carries the set, the name does not matter at all. And anyway -- I found a duplicate of it made in India posted later in the previous article, aand still quoted below. O.K. Edmund no longer carries anything of the sort, but I have found an example made in India to the same design. Just better packaging as it is in a hinged wooden case instead of a cardboard box. I have not found a price, but perhaps you can with more searching. Sorry about the extra-long URL http://anuuj.trustpass.alibaba.com/product/12241451/Spanner_Wrench_Lens_Opening_Tool_Tools_Adjustable. html Let me break the URL into sections for individual cut-and-paste if your system does not honor the '' and '' to keep it together: http://anuuj.trustpass.alibaba.com/product/12241451/ Spanner_Wrench_Lens_Opening_Tool_Tools_Adjustable. html Unfortunately I can't tell from that picture which tips are included. It looks to me as though there are one slot pair and two pin pair. Almost certainly both pin and slot tips, just as mine was. And -- since the tips are made from standard hex stock, you can easily make some for smaller or larger slots at need. Mine had 1/4" hex stock for the tips, but one from India is more likely to be 6mm hex stock for the tips. I forget whether the cross-bar was 3/8" hex stock or 1/2". It's also too big for my second application. Maybe, maybe not. The tips can be pointed towards each other or away on the smallest hex cross-bar. Note that there are three notches in the bars which are slightly angled. You can get a minimum spacing while tapering to the outside by interchanging the sides and moving to the notches closest to the tips. And normally you would select the shorter fat bar for the crossbar for that application. So -- the question is "what ID does it need to fit through, and just how deep? Or -- you can turn a cylinder to fit inside, with a knurl at the outside end, and either mill it to form screwdriver bits, or drill it and insert bits made from drill rod (silver steel). Note that I have made a deep reach spanner (to get to a nut in a 50 cc Honda many years ago) by taking a spare socket-wrench socket of appropriate diameter, and filing away everything except enough to form the screwdriver tips. This is an option for you too, with the additional benefit that you probably have a milling machine available, which I did not at that time. I've also been known to take needle nose pliers and file the tips down to the right thickness and angle to form a wrench for optical rings. There are *tons* of ways to do this -- depending on what tools you already have to hand. By the way, this is a ring spanner in the UK: http://www.britishfasteners.com/mm5/...00003/er14.jpg O.K. Not an open-end but a "box wrench" in our (US) terms. Enjoy, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#39
Posted to rec.crafts.metalworking
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Anyone know where to buy semi-silvered glass?
On 2008-03-06, Richard J Kinch wrote:
Christopher Tidy writes: I also need some lens-removing tools. Not sure what they're called. You must mean spanners. Edmund Optics, Thorlabs for some pricey ones. Ebay for a budget type. O.K. Looking under Edmund Scientific, I did not find them last night, but looking under Edmund Optics tonight, I find them. Try: http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=1457&search=1 complete with a link to download the (one-page) manual in PDF format. Often the rings are hardly tight, and can be turned out with the tip of a tiny screwdriver on one side, or the filed-down tips of needlenose pliers on both sides. Give it a try. Indeed so. Or make a special spanner as I described in the article which I just posted. Enjoy, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#40
Posted to rec.crafts.metalworking
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Anyone know where to buy semi-silvered glass?
"DoN. Nichols" wrote in message ... On 2008-03-06, Richard J Kinch wrote: Christopher Tidy writes: I also need some lens-removing tools. Not sure what they're called. You must mean spanners. Edmund Optics, Thorlabs for some pricey ones. Ebay for a budget type. O.K. Looking under Edmund Scientific, I did not find them last night, but looking under Edmund Optics tonight, I find them. Try: http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=1457&search=1 complete with a link to download the (one-page) manual in PDF format. Often the rings are hardly tight, and can be turned out with the tip of a tiny screwdriver on one side, or the filed-down tips of needlenose pliers on both sides. Give it a try. Indeed so. Or make a special spanner as I described in the article which I just posted. Enjoy, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- Try searching for 1/2 aluminised glass. Might yield better results. Steve R. -- Reply address munged to bugger up spammers |
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