Please help me understand True Position

That's pretty funny. AL isn't stable enough for splitting tenths, IMO. I'd bet there is 0.010 clearance on the mating part.

Who is going to inspect this bore?
 
Tony Wells said:
That's pretty funny. AL isn't stable enough for splitting tenths, IMO. I'd bet there is 0.010 clearance on the mating part.

Who is going to inspect this bore?
Click to expand...

No one. Especially not the person who will be whining about the cost.
 
I have found that in the "CNC" world we live in now, True Position is less relavent. It's supposed to give you "extra" tolerance but most inspectors really have no idea how to apply it and simply accept the part. Many prints are laid out wrong as the drafters love to reference TP to A-B-C because that's how they've seen it before.

I get where and why its used but in the industries I have worked it has not caught on - much like the metric system.

Jim
 
I had a job one time, when some metric machines were being installed in our plant. I was working night shift, I came in and the foreman showed me this tooling part, said something to the effect that this pocket has to be .078740 deep. No tolerance given. It was an area about 1 1/2 by 2 inches. When I received it it was about .05 deep. It took me about half an hour to find out that 1) the instructions had been passed by two or three individuals, 2) they had originally been "made it about 2 millimeters deep." Again, no tolerances given. The instructions had translated from German to English as "make this pocket exactly 2 mm deep". Turns out it was only for clearance so a part could move without hitting the bottom. Using an end mill I got it within .010 of 2 millimeters and everyone was happy. Sometimes accuracy is relative.

Edit to correct typo.
 
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