Looking for Dimpling Advice

[RVGator]

My dad and I recently attended the EAA RV builder's course. Basic Sheet Metal construction would be a better title but the course was exactly what we needed!

Below are photos of our project. (Don't laugh...it's our first try! Ok...laugh a little.) We never really felt comfortable with dimpling. It seemed there was always a little cup around the rivet. We were able to compare our results with some RVs out on the line. We noticed they all had nice flat rivet lines. We tried using less force when we hit the dimpler. Usually this resulted in a dimple that left the un-squeezed rivet above the skin. We tried using a squeezer with the same result. We were never able to create a dimple that was exactly the diameter of a 426 rivet.

So my questions are:

1. Had we squeezed a rivet that did not sit flush before squeezing, would it have shaped the dimple the rest of the way?

2. Has anyone discovered a good, consistent technique for dimpling?

3. How much will paint hide?







Thanks for the advice!

[Danny7]

Originally Posted by RVGator

So my questions are:

1. Had we squeezed a rivet that did not sit flush before squeezing, would it have shaped the dimple the rest of the way?

2. Has anyone discovered a good, consistent technique for dimpling?

3. How much will paint hide?

Thanks for the advice!

looks alright to me, as long as you are not using tank dies (they produce a little bit deeper dimple) i'd say to stick with using the dies to fully form the dimples and move on with building

if you are using a cframe to dimple you just whack the die holder with the hammer and move on to the next hole. tons of builders have used this method, or using a DRDT2 or a squeezer. adjust them so the dies just barely touch before full closing and you should get great dimples.

no, if you put a rivet in a partially dimpled hole the dimple will not change as you squeeze the rivet. all the force goes to squeezing the rivet and the rivet deforms under the pressure, so it won't transfer any force to the dimple shape. besides, you'd then have to have a force vector going inward on the dimple and that would mess up your rivet

hope this helps, i don't have any paint experience so don't have much to say there.

[N941WR]

Originally Posted by RVGator

...
So my questions are:

1. Had we squeezed a rivet that did not sit flush before squeezing, would it have shaped the dimple the rest of the way?

No. It will sit proud of the surface. Dimple the hole again.

Originally Posted by RVGator

2. Has anyone discovered a good, consistent technique for dimpling?

Practice. Simple as that. Build some tables to hold the aluminum flush with the top of the female die. (See this picture. Those two small "tables" can be moved around as needed.) Bring the male part down and stick it in the hole with one hand. Use the plastic head on a heavy rubber-plastic double headed hammer, like this. Hit the C-Frame once and hit it hard. No tap-tap-tap...

Originally Posted by RVGator

3. How much will paint hide?

A lot. When you are finished, get some Aerodynamic dent filler and fill the holes.

[redwards]

Those look like under-dimpled rivet holes. There is no particular finesse required for dimpling. You just have to hit them hard enough for the dies to come together completely. Smack the **** out of the c-frame, or, if using a squeezer, sqeeze as hard as you can.

[larrynew]

A couple of things to check. I'm no expert, just finishing tail kit and slow build wings well looked over by Tech Counselor and A&P.

Make sure they're not tank dimple dies. They dimple about 7/1000ths deeper.

If you're using a c-frame (I am), check that the bottom die is level with the surrounding surface when you're dimpling otherwise it can deform the skin a little.

[aerhed]

Primer will hide a "slight" cup around the dimple. All dimple dies are not created equal. Inspect yours carefully, you may want to modify the rim slightly with a file or something. As stated, keep practicing until your dimple quality is as good as your dies will allow.

[William Slaughter]

As long as you're getting the dimple dies closed all of the way down, whether by squeezer or c-frame and hammer or whatever, the final conformation and appearance of the resulting dimple is mostly a function of the dies themselves. While all of the major Van's tool suppliers have good quality dies, I've found that the Cleaveland dies give me the best looking results. In any case, don't be bashful about giving it a good whack in the c-frame, or adjusting the squeezer so that the dies touch and close fully.

[videobobk]

I gotta go along with Randall here. It is almost impossible (almost!) to over-dimple. Dimple a few holes in some scrap and look at the reflection in the metal. It should appear flat just outside the dimple with no wavy reflections. Everyone has there own way of hitting the C-frame. I like a light tap, then a good smack, if you are hand-holding a piece (not supported by a table.) The tap gives you a good idea whether the part is exactly square with the die. One problem that can happen with squeezing dimples is using a sprung head in the squeezer. I saw one 3" head that had been sprung open by about 0.020" and it would not give a good dimple--it was dimpled well on one side and showed wavy reflections on the other. The C-frame is the best!

I like tank dies for ribs and bulkheads, but that is another story...

Bob Kelly

[Flying Scotsman]

Was the material underneath countersunk, or dimpled?

If countersunk, make sure you didn't countersink too deeply.

[terrye]

These rivet holes look under-dimpled to me. Make sure you have good dimpling dies either from Avery or Cleaveland. Also make sure as others have noted that you are not using tank dies (have a -T in the stamped number). If using a C-frame make sure the material is perpendicular to the dies (I use a carpet covered table that is flush with the bottom die) and hit it with a dead blow hammer. I usually hit it twice to make sure. If using a squeezer adjust so the dimple is fully formed.

Note that top surface of the skin (where the rivet head sits) will have a radius so it is not going to look the same as if it was a countersunk hole, but the skin should be flat outside the die diameter.