Let the Record show that BillT on or about Mon, 14 Dec 2009 12:01:08 -0800 did write/type or cause to appear in alt.machines.cnc the following:
Friend of mine is getting a wee tad cranky over proposals to restrict personal tools on the floor. In part because he has used the company wrenches, and could not get the part seated with less than a .010 gap under it. Considering that the tolerance is .005 ...
And then there is the thermal expansion co-efficient. I've been told that some of the parts have tolerances which mean that once started, the machine cannot be stopped, as the program is set up with expectations of a certain amount of expansion. Let it cool off, and it will be finished wrong. One more reason for machining on second (after sundown) shift, especially in summer. Of course, in the winter,you have the reverse problem B-).
I keep recalling the one place I worked. Special Jobs were (iirc)
+/- 005 on spec, but all of it had to be within +/-.0004 of that dimension. Sometimes over a ten foot long turning. On manual machines which had been there since some war. Funky. And Jim had one part, which was +/- .0001, but right at the maximum allowable. I mean, right at it. Since it was going into a high pressure environment, it had sat for a year, while various outfits argued over whether it was in spec or not.tschus pyotr
- pyotr filipivich We will drink no whiskey before its nine. It's eight fifty eight. Close enough!