[CRUSH-build] making precision parts

[Bill Bennett]

Hi builders

The Tool group has been working steadily at learning how to use our shop to produce the parts we need. And I think it's starting to sink in that precision work takes much more attention and forethought than the rough cut part making we're accustomed to. This is all good news - learning how is why we operate in the fall. 

For example (and not picking on Joe - he's doing a great job): Joe has been working on making the shifter shaft that goes in the team 229 transmission. He's made three of them now, each one closer to "right". On the last, he had the length and outside diameter dimensions perfect, and started on the next step of drilling a hole in the center of one end. This is a 1/4" hole in a 3/8" shaft. The hole came out slightly off center. I have not measured it, but I'm guessing it's maybe 0.015 (15 thousandths) of an inch off center. This sound like a tiny amount until you realize that the amount of steel left between the inside diameter and the outside diameter is only 1/16", or 0.062, so off by 0.015 is quite a big fraction of the steel missing on the thin side, and the rigidity of the part is compromised.

That particular hole is a loose fit in the design, so it's probably OK. Nevertheless, the learning is to think about how to avoid the problem next time, when the precision might be important. I thought about this some last night, and I have some suggestions. Some of you are yawning at this point, some have already deleted the email, but hopefully the tool guys are still interested. I've put the text of this email, and the additional suggestions, in our team forums. Here's the link: http://wizardofaz.net/phpBB2/viewtopic.php?t=16

Bill
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