Drillbit size for countersunk holes

[Minicooper 35]

Hi guys.

Silly question from the German department:

What kind of drillbit (number or name) do I have to use to create countersunk holes for 8-32 and 4-40 (? the small black ones) flathead screws? I tried a "european" one but failed due to that Plup Fiction-ish inch/metrical problem ...

Thanks for your help

Sebastian

[FlyinGN]

you could use a much larger drill bit and just drill enough to countersink it.

[Minicooper 35]

The main problem is the angle of the screwhead in relation to the sunk hole. With the metrical ones the screwhead looks out of the hole. If I would drill deeper I would have a large crappy looking hole with a tiny screwhead in it. Especially with the 8-32's this also could create problems with the rear pivot support and the amount of material I have to make holes in it ...

[Eau Rouge]

4-40 uses a #43 bit (.0890") for tapping holes
8-32 uses a #29 bit (.1360") for tapping holes

4-40 uses a #33 drill bit (.1130") for clearance holes
8-32 uses a #19 drill bit (.1660") for clearance holes

4-40 flathead machine screws require an 82° countersink (common, hardware store)
8-32 flathead machine screws 100° countersink (try McMaster-Carr or other machine supply company)



The only way to get a good, straight countersunk hole is with a drill press with a chuck stop for depth. Anything else by hand is going to probably give you uneven results.

[Minicooper 35]

4-40 flathead machine screws require an 82° countersink (common, hardware store)
8-32 flathead machine screws 100° countersink (try McMaster-Carr or other machine supply company)

Thanks Apex

Seems hard to get them in Europe ...

[Tadracket]

Sweet info speed. that is going in the pocket pc.
Nice question coop. I always wondered that myself.

[Eau Rouge]

Try McMaster-Carr, I'm pretty sure they will ship internationally. Donno if it is worth it or not. Maybe someone on oOple.com can give you a better source in Europe for machine tools & supplies. I'm sure there is some place in Germany like McMaster that will carry tools like this.

From McMaster-Carr, I'd buy a #2742A512 (3/8" bit) in 100° for the 8-32s and a #2742A511 (1/4" bit) in 82° for the various 4-40 countersinks. That should be perfect for 99% of all R/C countersinks you'll ever need.


doug

[Minicooper 35]

Hi Doug

Jimmy "oOple" could be a good source. Otherwise the fellas at our UK department should know about sources ...

Cheers

Seb