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Old September 13, 2012, 05:35 PM   #2
Senior Member
Join Date: June 19, 2012
Location: East Texas
Posts: 407
It's been a long time since I worked in a machine shop. And I wasn't a machinist. I was a student who had taken a course, passed a hands on test building something and was given the keys to the shop. I made one of a kind stuff.

If you had asked me to make a 1" diameter rod and a 1" hole, I would have asked if you expected the rod to fit in the hole. If you said yes, I would have asked which diameter was more important to you and how tight you wanted it to fit. I could do a better job at making the rod accurate to within a thousandth of an inch or so than drilling the hole - with the equipment at hand. If you wanted a weird size hole, I'd have had to grind a drill bit to the right diameter.

I wouldn't have known what to do with your pin problem without looking at a reference book. As I recall, unless you make the pin, the manufactured pin defines the specifications of the hole. If you also wanted the pin made, I'd have still had to use the book. If you didn't pick a standard diameter, I'd interpolate between two pin - hole combinations that were in the book.

Bottom line is you need to let the guy know what you want to do with this or how you expect it to fit together. And since there are two variables, you need to let him know which one is "fixed". If he's decent - and most are - he'll figure it out.

I'll never forget the instrument maker who ran the shop and his reaction to a student who brought him a uniquely shaped template to make a mask for an experiment. When asked why he needed this oddly curved mask, the student replied, "It will make the Bessel functions work out right and the data easier to analyze."

He's lucky he's still alive.
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