View Full Version : countersunk screw angle

03-09-2010, 05:52 PM
what countersink (angle) do you use for which screw? tried searching. thank you, tom

03-09-2010, 06:22 PM
What countersink (angle) do you use for which screw? The 82 angle is used for screws with countersunk heads.
60 is used for lathe centers
90 & 120 are used for drill centers


Pete F
03-09-2010, 06:37 PM
McMaster-Carr sells both 82 and 100 degree screws. I'm guessing 82 is more common?


03-09-2010, 06:55 PM
American S A E is 82

Metric is 90

Some air craft stuff is 100

Lew Hartswick
03-09-2010, 06:56 PM
The 82 angle is used for screws with countersunk heads.
60 is used for lathe centers
90 & 120 are used for drill centers.
The 82 angle is used for screws with countersunk heads.The screws have "flat" heads and the 82deg is for US screws
90 & 120 are used for drill centersThe Metric Flat Head screws have 90deg angle . Don't know
what a "drill center" is. 100deg flat head screws are common in
the US for thinner materials, I've used them in the past.

03-09-2010, 06:59 PM
thank you for quick and informative replies!:D pigpen

03-09-2010, 07:09 PM
Don't know what a "drill center" is.Spot drill might be the [much] more common term.


03-09-2010, 08:22 PM
The fluted countersink cutter is used to provide a heavy chamfer in the entrance to a drilled hole. This may be required to allow the correct seating for a countersunk-head screw or to provide the lead in for a second machining operation such as tapping. Countersink cutters are manufactured with six common angles, which are 60, 82, 90, 100, 110, or 120, with the two most common of those being 82 and 90. Countersunk-head screws that follow the Unified Thread Standard very often have an 82 angle, and screws that follow the ISO standard very often have a 90 angle. Throughout the aerospace industry, countersunk fasteners typically have an angle of 100. The ideal countersink angle for holes tapped with 60 threads, when no countersunk fastener head will sit in the countersunk area, is often 60; but often another angle is used if that is the cutter that is at hand, and the difference usually doesn't matter.




Your Old Dog
03-09-2010, 08:28 PM
Just got an 82 degree from enco in cobalt for $19.00

Peter S
03-10-2010, 05:15 AM
Taken from my Unbrako catalogue (high tensile fasteners, the best you can buy in my opinion), they call them "flat head screws":

90 degrees: Metric, B.A, BSW, BSF threads.

82 degrees: UNC, UNF threads