DIY Calibration

[matthewsx]

In another thread it was mentioned that electronics hobbyists have a system of sending calibration standards around to each other so they can calibrate home shop equipment.

I’m wondering if there’s any interest in doing similar in this community. I could see it being based on our pass around box, but it would require someone who knows how to create the standards and write instructions for using them.

I’m not that person but I thought it would be worth pitching the idea here and seeing if anyone wanted to run with it.

John

 

[benmychree]

Calibration of WHAT?

 

[matthewsx]

Calibration of WHAT?

Measuring tools.

Mics, calipers, indicators, etc.

John

 

[3Dogs]

It’s an interesting idea.
I’m a bit of a metrology freak - I’m always curious about the accuracy of my instruments. In past lives, I worked in the semiconductor industry, and we had all kinds of neat measurement standards. I’ve had my pressure gauges and meters calibrated by NIST-traceable labs, but I’ve always wanted a Primary pressure standard (a deadweight tester).

As I gather tools to support my (soon-to-be purchased) milling machine, I had a decision to make - buy name-brand calipers and dial indicators, or try to save a lot of money and by Chinese tools, which might not be as accurate. I ended up buying a Shahe micrometer and a few test indicators. Then I bought a “B” grade Wen set of gauge blocks. In theory, each block is measured and the error noted, so I could use those to confirm the other instruments. When I measured the 1.0000” block with the caliper, it measured within 1/10,000” - which is plenty good enough for me. My other digital caliper was also right on.

The other two standards that are important is a flat surface and a right-angle. I found a small, used granite surface with inspection data for a reasonable price. I also bought a steel machinist’s square which is supposed to be accurate to 4/10,000ths over 8”, and a small Chinese granite square. I used a comparator and the granite surface to confirm that the granite square and the metal square read the same, to the limit of my test indicator (.0005 divisions). I’d like to get a cylinder square, but I need to stop buying stuff until I get my mill.

I haven’t bought a machinist’s level yet. I saw a great video on how to use them, but have been unable to find it again. The presenter talked about how to find the “level line” on any flat surface.

 

[Bone Head]

Calibration instructions is a great idea. I wrote instructions for an aerospace and a defense contractor when I worked as the calibration tech; I'd be willing to take a crack at such. It could be placed in Downloads, so everyone could have his own copy or print them out.
The one point which might prove tricky is setting tolerances. Not everyone would require what the next guy would use, so it would be an unprotected document so people could change tolerances to suit their needs.
Would Microsoft Word be an acceptable software for such?