How to dimple for a #8 screw with no cracks?

Brantel · Post by **Brantel** » Fri Oct 19, 2007 11:46 am

So you do a nice job drilling a clean hole for a # 8 screw using a #19 bit, you do a good job deburing both sides of the hole, then you take your #8 dimple dies and dimple the hole only to find that you have small cracks around the ID of the hole.

How do you prevent this?

cjensen · Post by **cjensen** » Fri Oct 19, 2007 2:21 pm

Don't know that you can, really. The bigger the hole being dimpled, the more of a chance you have of getting small cracks because the AL moves farther the deeper the dimple.

Got any pics of the cracks?

Brantel · Post by **Brantel** » Fri Oct 19, 2007 3:33 pm

No pics because the cracks are so small but they are there! They radiate from the ID of the hole to about half way down to the outer edge of the dimple.

I saw some when doing my tanks and Vans said that it is normal and don't worry about it.

Now I did the screw hole back on the rear fuse for the rudder cable guide and got the same results.

Brantel · Post by **Brantel** » Fri Oct 19, 2007 8:18 pm

I tried using a #16 predrilled hole with the #8 dies and it worked out great! No cracks and I measured the ID of the hole afterwards and it was no larger than one that was predrilled with a #19 so from now on #16 will be my drill of choice for predrilling for #8 dimples!