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Dimple vs. Countersunk

newrv-4

Member
My RV-4 partner is having trouble using the dimpler on on .032 skins.

"The dimpler works really well on the .016, but not great on .032.. I think maybe .032 should be countersunk... I'll look into it before I do any thick skins.."

While I feel that when it is not called for in the plans countersinking is not the way to go, I just wanted to get some support for or against from the group. Also are there any tips to getting a good countersink with the dimpler? I am currently traveling and am not able to get a look at the issue first hand. As always, thank you.
 
Which dimpler? The hammer style or something else? We probably need to know more before we can help diagnose the problem. With the proper tools and technique, 0.032 isn't hard to dimple.

I countersunk the tail skins and the tank skins on my RV-6. If I did it again, I'd dimple them. It is faster, more reliable, and provides a stronger joint.
 
I agree, .032 is no problem to dimple with pneumatic, hammer, or even blind dimple tools. I prefer to dimple any place I can for more pleasing, more consistent, and stronger joining. I don't own the manual type squeezer so I can't speak for those. It's always possible your dimple dies are poor quality. I've always preferred those from Avery but have had good results with other brands also.
 
Another note on countersinking. The material has to be thick enough for a particular size rivet so that it's not knife edged.

I don't have the reference handy, but can look it up if anyone is interested.
 
DRDT2

Get a DRDT2, soooooooooo worth the $. I love mine, I have had it since day 1, and recently had to dimple something the old fashion way (c frame and a hammer) because the drdt2 was packed up for a move. I am so glad that I have that tool. (It's still packed, awaiting my next airplane project;-))
 
From Vans' FAQs:
For AD3 rivets, .032 is the minimum allowable skin thickness [for countersink], and for AD4 rivets, .050 is the minimum thickness. Metal thicker than this is difficult to dimple, so it is common practice to machine countersink for AD4 rivets.

While it is acceptable practice to machine countersink metal as thin as 0.032? for an AN426AD3 (3/32?) rivet, we recommend dimpling in metal 0.040 and thinner. There are a couple of reasons. First, although RVs are designed so that a countersunk joint is acceptable, the interlocking nature of a dimpled rivet line is stronger. Second, dimpling leaves a thicker edge for the shop head of the rivet to form against, meaning that the metal deforms less and there is less chance of ?working? rivets later.

This recommendation is meant as a guideline, not an absolute rule. There may be instances where countersinking in 0.032? stock makes the job easier, and certainly can be used.
Personally I cheat with a Pneumatic Squeezer and will dimple whenever I can in preference to C/S ;) NB in thicker metal you can dimple, and then a touch of C/S to make the rivet fit well. If you are a perfectionist, set up the C/S tool, but careful use of a deburring tool (with/without the C/S end) might work OK...
 
What they all said!!

All the votes are for dimples..... so is mine.

I actually countersunk all the horizontal stab on my 4 and the finish is really smooth, but it is a decision I may come to regret as countersunk rivets are more likely to move and smoke.
 
0.032 should be easily dimpled. Get some local oversight from another builder to check technique.

If using a DRDT-2, the toggle clamp must be adjusted to fully lock with enough pressure to visibly spread the c-frame. It should "pop".

As Andy said, on thicker skins (above 0.040), you can dimple for the strength advantages and then finish with a few turns of a countersink bit to sharpen the hole and get the rivet nice and flush. The need for this was rare, but it is a method to get it done.
 
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There is a lot of useful information here. I think he will be able to get it to work with these reply. Thank you all.
 
Squeezer vs. C-frame

I usually used the squeezer everywhere it would work, on holes close enought to the edges on big sheets for example. The C-frame I used when the squeezer did not have the reach. This because it is much faster dimpling with the squeezer then the C-frame.

Ones when I had not dimpled a bigger sheet for quite a long time I actually forgot this and used the C-frame for the entire sheet and was wondering why it took so long, until I realized what I was doing. Only then did I realise what difference using the squeezer actually does. The thing is that usually quite a large amount of the holes are close to the edge and as the squeezer is so much faster it really does make a difference. Kind of obvious maybe, but I thought it might be worth sharing anyway.
 
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