[Calvin25]

Dimple/countersink questions?

The debured #30 holes that im dimpling seem to be opening up a little bit.

Is this normal? It is enough to cause a nominal amount of lateral play when dry fitting a rivet.

I may have over debured causing a weakness allowing the stretch???

-Or bad dimple die (Avery spring back #30)





For the inside mating surface of a part to be countersunk for a dimpled sheet, is it recommended to go .005? deeper then flush.

I recall reading that some where and want to make sure before I go too deep.

Thank you, -Bill

 

[Mel]

It's perfectly normal.

The debured #30 holes that I'm dimpling seem to be opening up a little bit.
Is this normal? It is enough to cause a nominal amount of lateral play when dry fitting a rivet.

Yep, dimpling will open up the hole slightly. this is perfectly normal. Build on.

 

[danielhv]

Exactly what Mel said. I think I've asked the same question. It will be even more noticable when you are dimpling holes larger than the #30.

 

[flion]

Mel, it was never an issue for me but I seem to recall that some folk (from the RV-list, which I haven't frequented in some time) advocated drilling to 1/8" and letting the dimple die open the hole to final size. Have you seen the technique used? Not having tried it, does it work or does it potentially cause some cracking around the hole? Would there be much advantage to a closer tolerance initial fit for the rivet since riveting is going to cause it to expand into the hole anyway?

 

[Mel]

Yes drilling to 1/8" is certainly an option. Some even drill with a #31, but it is not necessary, and it makes it more difficult to get the clecoes in. Drilling undersized will sometimes cause the dimple die pilot to expand the hole and create small stress cracks, so be careful.

 

[llavalle]

The other option is to use a reamer to open to #30. If you manage to drill a perfect hole with a #30 drill, you're ok but most of the time the hole end up a bit larger.

A reamer with be easier to handle and makes perfectly round holes. Best of all : the burr is smaller and easier to remove.

I've switched to reamers (#40 & #30) since after the HS and I'm not looking back!