Testing dimpling 0.032" thick material for #8 screws - 3 hours

So I have been practicing for the last two evening trying to solve how to eliminate the cracks. I've been on the phone with Vans for their advice, talked with friends, etc. Not to mention laid awake a bit a night.
For me, it doesn't matter if the hole is #19, #18 and #17, it can crack. That's not to say that going up a size or two on your pilot hole doesn't relieve some pressure, but I found that it wasn't the complete answer.

Just for kicks I drilled some #18 and #17 holes to see how it would go. I deburred the holes and dimpled them. They cracked.




So, for me that kinda solved the hole size issue. I did notice that there was a difference in hole sizes after they were squeezed. Its a bigger pilot hole, and after squeezing, surprise surprise, the hole in the dimple was larger too. Seeing that it did not eliminate cracks...I resolved to focus on the #19 holes. What seemed to be the common denominator in all my cracked holes was how well/clean the holes were drilled and the condition of the deburing. I holes were good, the cracked dimple was 1 in 28. Holes that were not as clean I got 1 in 10 cracked. It's easy to be sloppy with the drill in opening up the holes and its very easy to debur too much. My 3-flute deburring tool does not do a nice job when looking under a magnifying glass. The one hole debur tool is better, but its not perfect. 

I carefully drilled all the tank skin holes (39 test holes) up to #19. I started #25, #22, #20, then #19 (This process gave me brain damage the whole way...its not a great way to enlarge holes this way) Once I was done I then used a small piece is 600 grit sandpaper on my Dremel, (Just a small piece wrapped on the mandrel. I carefully polished the holes (It took a long time to prep the holes) but they looked great.

Here is what a marginal hole looks like. This is likely to crack. 


This is a #19 hole that was final polished with the 600 grit sandpaper.



 At the suggestion of a friend to lube the dies, I sprayed WD40 on the work and the dies and started squeezing. All 39 holes made beautiful dimples and no cracks!


For me this was a bit of a win. I feel confident that I am on the right track, but I still want to perfect the process. I'm still waiting for a #19 reamer to arrive and I may abandon the deburing tool completely. As you can see from the pic its not a perfectly clean edge on the dimple, they are some very tiny jags on the edge. I may use the Dremel felt and polishing compound to debur the edges instead.
 I am one step closer to solving this.