Included angle of drywall screw head?

I just measured a #6 drywall screw and it has a 3/16 radius from shank to od of head.

So much for angles, eh?? If only I could see outside the box.... LOL

So if I am to c-sink aluminum, anticipating dry wall screws, what would be a good compromise? Heh, mebbe this a clue NOT to use drywall screws, eh??

thanks.

I was going to ask why the heck you're using drywall screws in aluminum, but I thought better of asking. Then we might have to deal with the answer. d8-)

IIRC it has been mentioned here before that the smaller metric countersunk screws are 90 degrees but the larger ones are as per US and

I can tell you from very expensive personal experience that 82 and 90 deg screws are both common for #6 and #10, and that a good ME will select the proper angle based on the thickness of the material being held, but that getting them mixed up on a production line can cause no end of grief.

Aluminum *to* wood. See reply to Bill.

I thought all regular drywall screws had bugle heads, for which no cone angle will work.

Looked it up:

Trim drywall screws do have 60 degree conical heads, and one can easily buy 60 degree countersinks.

The various cone angles came from mechanical tests of what angle had the best combination of properties for the material at hand.

The 82 degrees is best for steel.

The 100 degrees is the best dimple angle for sheet aluminum used to make airplanes in WW2.

The 90 degrees is the Metric world saying just-split-the-difference, so they don't need to have two kinds of screw.

As for the 120 degree heads, I have to guess that its for very thin panels, where the screw forms the dimple. And for wood, I suppose.

Joe Gwinn

The screws with 180° heads are really useless. ;-)