Aircraft Tools Blog

Setting Perfect Dimpled Flush Rivets

I am always surprised that many RV builders have not tried this.  We do it all of the time on our production STC's kits when flush rivets are installed.  It takes a few seconds on each flush rivet, but produces the best quality rivet.

The facts are that no matter what dimple die you use for dimpling 02Thin skin you will not get a professional dimpled rivet unless you finish the dimpling process when you set the rivet.

Everyone selling tools has the best dimple dies on the market! Some suppliers claim to have developed and hold the secret to the perfect springback dimple die after years of fine tuning. I don't know if they are dazzling you with their genius or baffling you with BS. What I do know is that the "perfect" 100-degree springback dimple die was perfected in 1942. Everyone that builds springback dimple dies today uses the original 1942 design with very little difference.

I constantly hear and read that dimples are too deep or too shallow and the dimple die is generally blamed for this. The real problem isn't the dimple die, it's the process for installing dimpled flush rivets.

Lightly debur the holes. Very lightly so you don't actually cut any metal away, only knock off the rough burrs. After deburring you are ready to dimple the parts and prepare for assembly.

In order to do a professional job you will need to start with the dimple die to make the initial dimple. This is done by impact or pressure on the dimple die set using a DRDT-2 dimpler, C-Frame dimpling tool, hand squeezer or pneumatic squeezer. After the dimple is formed in the skins, stringers, ribs, bulkheads and all parts for assembly you will need to go to the next step.

Make a tool. Yes, that's right. Make a dimple set block. Make this by drilling a hole and countersinking it to match your rivet head depth in a scrap piece of steel or bucking bar. Next, use the dimple set block.

Install a rivet in the skin, place the dimple set block on the back side and lightly drive the rivet into the dimple set block. This will "set" the aluminum and the rivet tight and flush. When you do this it only take two or three taps with the rivet gun at low throttle. This draws all of the parts tightly together and makes the rivet tight in the dimpled holes.

Next drive the rivet using a standard bucking bar and you will have the perfect flush rivet.

This is a lot more work than would be required if you had the "perfect" springback dimple die. Unfortunately, many claim to have improved upon the springback dimple die developed in 1942 by NACA. Few, if any, have come up with a new unique design for a tool that installs a rivet into aluminum sheet that hasen't changed since 1942. Preset your flush rivets using the dimple set block and you won't need to spend hours trying to figure out who makes the best 1942 springback dimple die or why your flush rivets just don't set right in the dimple.