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What countersink use for 4/40 and 8/32 Associated Screw ?
Thanks

4-40 is 82*
8-32 is 100*

gomachv wrote:4-40 is 82*
8-32 is 100*

Ok for the angle but what diameter size 1/4, 3/8 ? (for exemple ,i founded : 3/8" 100 DEGREE 6 FLUTE CARBIDE COUNTERSINK )
Thanks

Diameter is not important as long as it's wider than the screw head. 3/8" will work fine for either.

Arrrgghhh,

this is SO frustrating!! I was aware that the 8-32s are 100°, but I assumed they all were 100° or the rest at least 90°.

That's what happens when your head is metric I guess.

At least Home Depot has 82° in stock.... I just received my 100° yesterday

you'll find that the 100 degree #4 screws fit beautifully in the chassis bottom, almost like they were countersunk for 100 degree screws. I'm pretty sure they were, and associated used 82 degree screws by default. either that or the countersinks were not sunk enough to allow 82 to be flush.

I have a bunch of aircraft stainless 100 degrees I use for most builds using rc10 gold/black pan, and most graphite as well. I hate how the stock 82 don't sit flush (and rust)

Yes, but since I converted a graphite chassis to mid motor, I need both countersink drill bits, 100° and 82°. Thinks would have been simpler iff all used the same angle.

I assume that the original tub chassis is too thin for the 8-32 screws to have a 82° or 90° countersink. The flatter 100° does not have this problem.

At least I'll have the correct bit to make all screws sit flush now.

Yeah, I always assumed they used the 100-degree 8-32's because the chassis material was too thin for more "normal" countersink angles as well.

Generally, only metric have 90 degree heads.