harbor freight micrometer

This is a forum to share experiences and ideas about holography.
Thieu

harbor freight micrometer

Post by Thieu » Sat Sep 11, 2010 3:30 pm

I use the mica from heatsink isolators. It's used to electrically isolate a transistor from a heatsink while keeping it in good contact thermally. It's kinda like the opposite of what you're looking for, thin, small and full of fractures. For optical grade mica you can try tedpella.com. They have plates and disks, however not as thick as you mention. I think 1 mm is quite thick for optical grade mica. But since it cleaves atomically flat, it may be possible to stack plates without creating a visible boundary.

Joe Farina

harbor freight micrometer

Post by Joe Farina » Sat Sep 11, 2010 3:35 pm

Regarding the harbor freight micrometer, I noticed that the product manual is available on that page also. Here it gives a resolution of 0.00005 inch, which would be very good I think. For measuring DCG, the edges of the plates should be scraped clear of gelatin anyway (for sealing), so it should be easy to take a measurement, scrape the gelatin away using a razor blade, and then take another reading at that same spot. The sale price on these micrometers should be $30 or less.

Colin Kaminski

harbor freight micrometer

Post by Colin Kaminski » Sat Sep 11, 2010 8:26 pm

Thieu wrote:I use the mica from heatsink isolators. It's used to electrically isolate a transistor from a heatsink while keeping it in good contact thermally. It's kinda like the opposite of what you're looking for, thin, small and full of fractures. For optical grade mica you can try tedpella.com. They have plates and disks, however not as thick as you mention. I think 1 mm is quite thick for optical grade mica. But since it cleaves atomically flat, it may be possible to stack plates without creating a visible boundary.
I am actually looking for cleavable pieces for making etalons and waveplates. Thank you for the link.

Ed Wesly

harbor freight micrometer

Post by Ed Wesly » Mon Sep 13, 2010 3:17 pm

I have seen but not used two devices for measuring thin films. ellipsometers and ultrasound. The ones that I have seen were produced by Gaertner of Chicago, and maybe one can find them in the surplus bins, for if you Google ellipsometers you will find plenty, starting at $10k+. But it looks like one could cobble up the optical path as illustrated in some of the manufacturers' web sites, however I get to a certain point and can't figure out what they're doing with the reflection information to find the thickness. Also one of the sites cautions against using this technique on films thicker than 10's of microns, which is kind of the range we're dealing with.

When I worked at a company called Magnaflux, inventors of the magnafluxing technique of non-destructive testing, they had ultrasonic echo devices to find thicknesses of thin films, like paint thickness. There was an ultrasonic trnsducer on top of the sample, and the operator had to look at an oscilloscope-like device to read the time delay between two reflections to figure out the thickness. This was in the mid-'80's, so not everything had gone digital, plus knowing Magnaflux this was a machine they probably started producing in the '60's and never updated.

So either of these devices might be able to be found in surplus places and revived. I know how everyone just loves those kinds of projects around here!

Also, "Here it gives a resolution of 0.00005 inch" which is five hundred-thousandths of an inch, which equals 1.27 microns, which ether makes me shake my head in disbelief or give kudos to a company that can make a mechanical device that is that accurate! I just showed the "Powers of Ten" video to my Optics classes last week, and one of the landmarks is at "10 microns, the diameter of a ruffly lymphocyte" (white blood cell). Maybe there's one too many zeroes in the resolution, or it's just that good!

From your favorite math teacher.

Joe Farina

harbor freight micrometer

Post by Joe Farina » Thu Sep 16, 2010 6:01 pm

I bought one of these micrometers today, but I was wondering how to verify its accuracy. I seem to recall Dinesh saying that a certain kind of food wrap (saran wrap or something similar) is supposed to have a certain thickness in the same range as DCG layers, which can be used as a guide. But that doesn't sound like a very reliable method for calibration unless the food wrap thickness is definitely well-known. Does anyone know of a standard material (film, tape, etc.) that is supposed to have a certain thickness? My planned coating for dye-sensitized DCG is around 20 microns.

JohnFP

harbor freight micrometer

Post by JohnFP » Thu Sep 16, 2010 6:26 pm

Those 4 mil trash bags are 4 mil. But plastic is going to be hard to measure.

You can buy stanless steel down to 1/2 mil and it's pretty right on.
1 mil = 25.4 microns


I wonder if it mentions the thickness of aluminum foil on the box? Or if you and inquire to the company about it?

Joe Farina

harbor freight micrometer

Post by Joe Farina » Thu Sep 16, 2010 6:55 pm

Thanks a lot John. I didn't realize shims went down that far, but I just checked www.mcmaster.com and they have plastic (polyester) shims at .0005" (12.7u), .00075' (19u) and brass, stainless, and plastic at .001' (25.4u).

This harbor freight micrometer is looking pretty good. The digital readout can be switched to millimeters and the scale reads 0.000 so it has a millimeter resolution of .001mm (1 micron) at least according to the readout.

I measured some saran wrap, and it came out at 0.010mm or 10 microns.

Thieu

harbor freight micrometer

Post by Thieu » Thu Sep 16, 2010 7:01 pm

The copper layer on bare printed circuit board has a pretty precise thickness. Standard thicknesses are 9, 17.5, 35 or 70 um. Most often it's 35. You can pull it off by cutting under it with a scalpel in a corner and then pulling it off further.

Another option that comes to mind is using a thick (phone)book with page numbers and dividing its measured thickness by (half) the number of pages.

Joe Farina

harbor freight micrometer

Post by Joe Farina » Thu Sep 16, 2010 7:13 pm

Thieu wrote:The copper layer on bare printed circuit board has a pretty precise thickness. Standard thicknesses are 9, 17.5, 35 or 70 um. Most often it's 35. You can pull it off by cutting under it with a scalpel in a corner and then pulling it off further.
Thanks, Thieu, that's a good idea. When I buy bare pcbs, they do tend to state the copper thickness in microns.

Joe Farina

harbor freight micrometer

Post by Joe Farina » Thu Sep 16, 2010 7:19 pm

I did a quick search for the thickness of saran wrap, and it was given as 12.7 microns, or 1/2 mil.

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