Maximum Material Modifier for Press fit holes

[Madhu454]

Hi All,
Need help with choosing the correct material modifier for press fit holes (H7), while using a positional tolerance.
Need to position TWO HOLE PATTERN (Diagonally placed on a rectangular plate) with a position tolerance, Dowel pins to be fitted to these holes, these dowel pins(m6) will be used to locate the top plate which fits on this.

> for positioning these holes, can I use Maximum material modifier for the pos.tolerance? or is this be with RFS ?
> if we use RFS how to distribute the tolerance for position, and still achieve the desired fit.

Please do the needful.

Thank you

 

[greenimi]

I would use planar surface primary and one hole secondary (with perpendicularity RFS to primary). The third hole positioned at MMC to primary and secondary RMB (no datum feature shift available from the press fit hole).
Highly unlikely that the two holes will act as pattern (again as pattern) as RFS holes.

 

[drawoh]

Madhu454,

The general assumption behind MMC/MMB is that if you are somewhere near LMC/LMB, you can make your positional tolerance looser.

There is a practical problem here. A hole that allows press-fits, is very accurate. Specify a reasonable positional tolerance. Add to this the bonus tolerance for your LMC. What have you accomplished?

I have never applied MMC/MMB to a press-fit hole, or a tapped hole for that matter.

--
JHG