RC10Talk - The Net's Largest Vintage R/C Community

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

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

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 ...

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.

apexspeed wrote: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 ...

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

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

Hi Doug

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

Cheers

Seb