Non metric countersunk holes

ok, so for a while, i have been doing the autofold option for countersinking holes. Its easy for metric since they are basically a 45,45,90 triangle. So whatever your offset is, thats how deep you push the autofold.

I have also tried the scale tool, uniform from center to make a countersink, but thas more difficult if you dont know any of the dims of the screw.

But whats the best way to do this for imperial screws that do not have same depth as the offset?

Is autofold still the best option? or is the scale tool better?

At one point this phrase was thrown around “The P/P Cardinal point method.” but i could not find an explanation of what this means.

However, the big question, does it really matter if they are accurate? because in al reality, a machinist or woodworker is going to have the tools to drill them to the correct dims anyway

The last thing. Unless the countersink is nonstandard, you really don’t need to specify the angle for woodworking and you can just type the correct angle when adding the label, anyway.

Ok, thats what i thought. I was drawing up something, and ran into that issue of non standard, but didnt really know if it needs to be spot on with drawings or just call it out on the drawing itself.


Countersinks for imperial sized screws are not non standard. Instead of the 90° included angle of countersinks used for standard metric screws, standard imperial flat head screws have a countersink angle of 82°. This is a common thing. Unless you’ll show the countersink large enough so that the angle can be accurately measured (and expect whomever is reading the plan to measure it) there’s not much reason to worry about it. You could probably draw them the exact same way you do for metric screws. If it is something you are modeling for 3D printing and screw fit will be important, I would expect to need to cleanup the countersinks with a tool anyway so I’d either not countersink the holes in the model or I’d model the hole to guide the countersink but include material to cut away to make the countersink correct.