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| A quickie alky lamp |
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| Lew_Merrick_PE:
--- Quote from: Bernd on July 22, 2010, 07:47:24 PM ---Great recovery on that goof. I'm sure that was a bit disheartening at first though. --- End quote --- Herr Meister Muller, owner of the shop I apprenticed in gave me the definitions for apprentice, journeyman, and master that are appropo. "An apprentice, he makes a mistake and knows not what to do. A journeyman, he makes a mistake and fix it he can. A master, he sees the mistake before he makes it and avoids it." Four decades in the "trade" and I am still only a journeyman. |
| Bernd:
Well Lew, sounds like you need a bit more practice,right? :D Bernd |
| Lew_Merrick_PE:
--- Quote from: Bernd on July 29, 2010, 09:22:06 AM ---Well Lew, sounds like you need a bit more practice,right? --- End quote --- Hey, I've never screwed up a job so badly that I could not get new material and make it right! Back in 1972 they changed the reference temperature from 70°F to 20°C (68°F). I was working a NASA job making rollers that were ø1.750 +0/-.000050 tolerance. I have no idea why such a tolerance was applied, but that was the job. I lapped all 24 of them to size -- and then discovered that the inspection chamber was set to 70°F. When I cooled it down to 68°F almost all the rollers were small! Peder Muller (no relation to Herr Meister Muller), a Dane with whom I worked on numerous contracts, took them and froze them in liquid nitrogen -- and then struck them all using a brass bar dropped (using a guide) from 18 inches. They all came "to size" within a couple of "hits." (The liquid nitrogen freeze transmitted the force such that the rollers expanded consistently along their length -- a truly slick trick I have been able to use a couple of times since then.) |
| Tinkering_Guy:
Never heard of that trick before. :bugeye: I assume you mean the rollers were struck along the axis? So they gained diameter but lost length? |
| Lew_Merrick_PE:
--- Quote from: Tinkering_Guy on July 29, 2010, 01:25:51 PM ---Never heard of that trick before. :bugeye: I assume you mean the rollers were struck along the axis? So they gained diameter but lost length? --- End quote --- Yup. The lengths were +0/-.010. It was the diameters that were (stupidly) critical. As I said, I have no idea why such tolerances were applied. I have used functional tolerances in that range a couple of times when dealing with optics, but I designed adjustments in such that they could be "set" at the last minute using nulling techniques. |
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