So i have the SWB servo arms, and they come tapped at 4-40. If i wanna convert the tap to M3 can i just go straight into the 4-40 thread with a M3 tap or should i drill out the threads first and then do the M3 tap?

Try a test using a thin piece of aluminum. Drill and tap for 4-40 and then try it both ways with the M3 tap.

Swb also makes servo arms tapped to 3 mm if you can still return those.

Drill , then tap ..
Works every time

Originally Posted by jhelber08

Swb also makes servo arms tapped to 3 mm if you can still return those.

Do they? I swear i didnt see them..

They dont make the 4.5 inch arm in m3

and theyre yellow..

You can drill and tap, but if you have a good quality tap, use some thread cutting oil you can tap it as is. Back the tap up a 1/4 turn or so as you go so it doesn't bind, blow the chips off before you back the tap out and you'll be golden. Done it lots of times and never a problem.
the drill size is only .009" diff btwn the two with the 3mm obviously being bigger.

Run the tap thru the 4-40 threaded hole. Just use some type of an oil to lube the tap. I chucked my 3mm tap in my drilland tapped 4-40 arms thay way.

Originally Posted by Hoverlow44

and theyre yellow..

Yeah they are kind of an off-gold, I have a few and I'm not sure why they picked that color. Should have made them neutral silver or black. I don't care for the yellow/gold color myself.

As to the original question, drill then tap..

yeah i have some tap magic, which is an aluminum cutting and tapping lube.

did you guys experience any slop due to slight bit of play /after some flights, from the 4-40 arms tapped to 3mm ?

Originally Posted by TBone08

did you guys experience any slop due to slight bit of play /after some flights, from the 4-40 arms tapped to 3mm ?

Did it many times. But i do put a lock nut on the bottom side. Never had one get loose.

+1 ^

glad to hear, did it yesterday first time, and was advised against it today due to slop in the holes.