Location tolerance of a hole at MMC with varying size dia's

[dtmbiz]

I have a simple 13mm plate with a thru hole of 25mm +/- 0.5 and a location tolerance of 1 mm at MMC.

On one side of the plate the actual hole measures 24.5 allowing a 1 mm tol zone. The other side measures 25.5 allowing for a 2 mm tol zone.

What determines the bonus tolerance size considering varying measured hole sizes (within size limits) thru the part?

Does the smallest diameter measured dictate the bonus tolerance?

 

[Belanger]

Yes, it's based on the "actual mating envelope" -- think of a perfect cylinder (not constrained to any datums) that expands until it locks onto the actual hole's surface. That determines the amount of bonus tolerance.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[SteveMartin]

(assuming ASME Y14.5M-1994)

The bonus tolerance available due to the MMC modifier is based on the actual mating size (ref. para 1.3.26 & 1.3.11), which for an internal hole is the largest perfect form cylinder which would just fit into the hole contacting at the highest points.

In short: yes, the smallest diameter dictates your available bonus tolerance in this case.