How deep should I dimple?

tvlawyer · #1 10-23-2006, 06:42 AM

When dimpling a rib flange, should I use the same depth dimple as the overlying skin, or slightly deeper?

What is the "measure" by which to set the dies? I am dimpling with my pneumatic squeezer and a DRDT-2.

mgomez · #2 10-23-2006, 06:53 AM

Squeeze until the dies close upon the aluminum...dimpling dies are not adjustable.

TerryWighs · #3 10-23-2006, 10:41 AM

Dimple should match the overlying skin...If the dies do not meet adequately together, the skin/rib will not seat as well. Also, an under-dimpled hole can contribute to a rivet setting "proud" on the skin...
I use a cotton glove test on the skin. After I dimple the skin, I loosely place a rivet in the hole...gently rub my finger over the surface wearing a cotton glove...the cotton glove should not catch the rivet...If you leave a circular ring imprint on the skin after dimpling...I try to back off a bit on the adjustment.

tvlawyer · #4 10-23-2006, 10:53 AM

Quote:

Originally Posted by TerryWighs

Dimple should match the overlying skin...If the dies do not meet adequately together, the skin/rib will not seat as well. Also, an under-dimpled hole can contribute to a rivet setting "proud" on the skin...
I use a cotton glove test on the skin. After I dimple the skin, I loosely place a rivet in the hole...gently rub my finger over the surface wearing a cotton glove...the cotton glove should not catch the rivet...If you leave a circular ring imprint on the skin after dimpling...I try to back off a bit on the adjustment.

The question I have is whether the underlying dimple needs to be a little larger than the upper dimple. Think about one soup stacked atop another of the same dimensions. One does not fit completely within the other. When dimpling, do I need to make my lower "bowl" larger so the upper "bowl" fits completely within it? I'm thinking that if it is even possible to make the dimple smaller or larger, then I don't have the stroke set properly to begin with.

My dies line up perfectly whether they be on the squeezer or the DRDT-2. I set them so they are just touching at the full stroke of both machines.

sprucemoose · #5 10-23-2006, 11:11 AM

Larry,

Dimple dies are not adjustable. A properly formed dimple comes from full application of "squeeze" to the dies. There is no way to under or over-squeeze to make a larger or smaller dimple, and still have an acceptably shaped dimple. Dimple dies (better ones, anyway) are design to go slightly past the ideal dimple shape, and the aluminum "springs back" into shape, hence the term "spring back dimple dies."

To make a larger size dimple, you would need a dimple die machined to produce such a dimple. Fortunately such a thing exists, and is known as a tank dimple die. Tank dies are designed to produce a dimple which is 7 or 8 thousandths deeper than standard dies, to make up for the thickness of the proseal under the rivet. I have heard of people using tank dies for underlying structure and standard dies for the skins, in order to achieve what you have described, but I don't think it's worth it.

TShort · #6 10-23-2006, 11:12 AM

The only way to make the dimple itself deeper is to get different dies - like the fuel tank dies available from cleaveland tool. If you push harder, set the dies a little closer together, etc. it will not change the depth of the dimple.

You will see that this is a non issue when things are riveted - the dimples nest nicely and things come together flush / tight.

Thomas

thallock · #7 10-23-2006, 11:14 AM

Larry,

I think the answer to your question can be deduced by answering another question. If you were going to dimple the underlying skin more than the top skin, how would you accomplish that?

Cheers,
Tracy.

tvlawyer · #8 10-23-2006, 12:19 PM

Thanks all. You answered my question.

RScott · #9 10-23-2006, 06:41 PM

I have a different answer, probably not to your original question.
I took a strip 12 or 15" long, drilled about a dozen or more holes in it and set my squeezer so the faces of the dimple dies just touched the surfaces of the strip & dimpled 4 holes. Turned the adjustment half a turn tighter, dimpled the next 4 holes, etc. What I found was that the looser the dimple, the greater the curve was put into the strip of metal. The tighter the dies, the straighter the metal and the less distortion. So I always adjust my dies so the 2 faces touch each other without any intervening metal to maximize the dimpling pressure.

N674P · #10 10-23-2006, 07:05 PM

Quote:

Originally Posted by RScott

The tighter the dies, the straighter the metal and the less distortion. So I always adjust my dies so the 2 faces touch each other without any intervening metal to maximize the dimpling pressure.

What RScott said, and a "halo" or circular imprint around the dimple is actually a good thing. That halo is what you see after smacking a C-frame, and means you have a nice "crisp" dimple, making for a smoother surface. I'm not making this up - it's what Randy Lervold told me at my first DAR inspection!
I have since been able to get these halos with both my pneumatic squeezer and DRDT-2. The dimple dies should be set as RScott says - you shouldn't be able to turn them when they're squeezed together. When dimpling, just pull the DRDT handle all the way down. The pneumatic trigger should be "slapped" fully closed - actuating slowly like you would when riveting wont give you a "crisp" dimple.