Converting rectangular tolerance to round tolerance (GD & T)

[ashivu123]

We are implementing GD&T on old drawings. Holes in the drawings are located in XXX +- .010 Tolerance.
Rivets are getting attached in next assembly for holes. Having following questions
1. Shall I convert +- .010 tolerance to round tolerance as Dia .028 as positional tolerance
2. According to assembly considering MMC of rivet dia and MMC of the (floating fastener formula getting .002 tolerance.
Let me know how can I include above tolerance in drawing .

 

[drawoh]

ashivu123,

If ±.010" is working, a true position of Ø.028" should work. Do you believe that someone actually worked out the tolerances? Maybe your fabrication is way more accurate than your specified tolerances.

MMC/MMB allows you use looser tolerances when your holes are bigger. Your tolerances can be significantly looser if your holes are significantly bigger. Are enlarged rivet holes acceptable? Can you switch from rivets to screws?

I am not an expert on rivets. I recommend that you read up on them carefully. Traditional iron and steel rivets are installed red hot. They cool to ambient temperature and they shrink accordingly, resulting in a clamping force. It does not appear that you are using these. Aluminium rivets are installed cold, and they do not shrink. I would assume they are loaded entirely in shear.

Consider using screws, and either nuts, or some sort of thread insert. I really like self-clinching nuts, especially the floating type.

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JHG