[DaninVan]

Well if the hole (collett) is .250 than the shank has to be smaller (.249) otherwise it ain't gonna fit.

 

[DaninVan]

Things they never told us in 'shop'...
https://www.engineersedge.com/manufacturing/drill-mechanical-tolerances.htm
I did not know that.
That would bring up the obvious question, what if you actually want a hole .250"
Everything manufactured has upper and lower acceptable tolerances (ie .2493 to .2489 for example...no idea what the actual parameters are).

I'm guessing you need to place a custom order. I know that my machinist neighbour worked to incredibly exacting specs in the aero-space sector.

 

[DaninVan]

From that last link...
https://www.engineersedge.com/general_tolerances.htm

Not woodworking then?

 

[DaninVan]

Very interesting Dan, it reinforces what I have said on this forum many times when members talk about attempting to get to 0.001" in wood!! Such members seem to forget that, unlike metal, it moves with the weather, even if 0.0005" is achieved on the day, tomorrow the sun may not be shining and it's raining, how accurate is it then?

That reminded me of the conversation I had with the owner of an Italian coffee shop/restaurant. He was explaining to me that they grind their beans for the day based on the weather! Apparently it makes a big difference in the quality of the finished product, the cup of coffee.
(He also said that the roasters of Starbuck's beans should be in jail... )

 

[DaninVan]

"Getting back on track, Pat Warner once said what he thought was the maximum allowance in shaft size. Does anyone remember what it was? I'm sure it was less that 2 thou but it seems to me that it wasn't much under that."
-Charles

https://www.engineersedge.com/general_tolerances.htm

 

[DaninVan]

I'll do a screen shot...it's a generalized reference, not specific to collets. I think you'd need to extrapolate from it.