Counter bore depths

[Wraith]

Can anyone tell me the standard counter bore depths for SHCS fasteners with Hi-Collar Lockwashers.
Metric and Imperial.

Thank you,
Wraith

 

[swertel]

That depends on the size of the SHCS and the lock washer.

McMaster Carr sells high collar lock washers with thicknesses ranging from .022" to .375".

The standard c'bore depth for SHCS is the same as the nominal diameter of the screw because the screw head height is the same as the nominal diameter with +.000/-.XXX tolerance.

Personally, our department uses a "standard" c'bore depth of nominal screw diameter plus .020 because of our dimensional tolerances.

If you have a more specific question, please elaborate.

--Scott

 

[Rentapen]

Wraith,
Nothin' gets under a tool, diemakers or assembliers skin then someone who cuts a c'bore to a screw diameters depth. Besides the tolerance of cap heigth, wear on the pilot-c'bore step drill outside radius, sprung lock washers or plain washers, and chips in the hole, when they assemble, the head always sticks up over the steel needing a dis-assembly to recut the hole depth. In the old days you set your depth from the thread depth and the thickness under the c'bore using a stock screw "under the head length" ensuring at least a sixteenth clearance between the shcs and the top of plate to allow for stuff on the screw.
Just wandering
rentapen