Dimpling/Countersinking for Tri Gear Spar Tunnel Fittings

[Gunther]

Hello to all. For you tri-gear folks, how did you dimple/countersink the tunnel Z for the 3/16" tri gear machine screws (MS-24694-S54)? What method provides the best results?

Sonex suggested making a die with a 100 deg countersink and dimpling the 0.032 tunnel Z into the die with a 3/16" flush head machine screw. This method tends to distort the surrounding metal and the dimpled hole becomes much larger than 3/16", measuring about 0.221 - 0.225".

I also tried a #10 dimple die and c-frame from Cleveland Tools and it makes a beautiful dimpled hole much larger than 3/16" and #10 as well, even when starting with the smallest possible pilot hole, #13. I also find that the dimpled 0.032 bottoms out in the counterbore unless bored to the absolute max depth of a knife-edged hole.

I obviously don't know what I'm doing. Any thoughts and suggestions are most welcome.

Gunther

[ScottM-Sonex1629]

Gunther,

This may sound crude,but if I recall, my method was to drill close to final hole size, and then use a machine screw that was the correct size, and lay the thinner Z-tunnel piece over a black of wood, and hammer home the machine screw to form the final countersink. KISS

[Concorde]

Hello to all. For you tri-gear folks, how did you dimple/countersink the tunnel Z for the 3/16" tri gear machine screws (MS-24694-S54)? What method provides the best results?

Sonex suggested making a die with a 100 deg countersink and dimpling the 0.032 tunnel Z into the die with a 3/16" flush head machine screw. This method tends to distort the surrounding metal and the dimpled hole becomes much larger than 3/16", measuring about 0.221 - 0.225".

I also tried a #10 dimple die and c-frame from Cleveland Tools and it makes a beautiful dimpled hole much larger than 3/16" and #10 as well, even when starting with the smallest possible pilot hole, #13. I also find that the dimpled 0.032 bottoms out in the counterbore unless bored to the absolute max depth of a knife-edged hole.

I obviously don't know what I'm doing. Any thoughts and suggestions are most welcome.

Gunther

So how did you do it ?
I'm practicing with a 3/16" machine screw on a piece of scrap and am not very happy with the results.

Scott, You said drilling to almost final size and then using the screw , but how did you put the 3/16 screw into a smaller hole ?
Thanks .