Ok, so I want to install better couplers on an old Mantua flat car that has the couplers as part of the trucks. I’ve dumped the old trucks and have some cool Proto 36" trucks that I’ve test installed and they will work fine.
Now, I want to put the Kadee #5 coupler boxes on the underside and would like to use a 2-56 screw to hold each box in place. So I have to drill a hole and “tap” the hole. I have a modeler’s tap set, …but what size of hole do I drill to properly tap the hole to a 2-56 size? Help from the pros here??
A No. 50 tap drill will do the trick. Kadee has a tap and drill set No. 246 that has the 2-56 tap, No 50 tap drill and the No.43 clearence drill for thru hole applications…Hope this helps…John
Thanks, jwar…I’ll see what the toolbox holds…
ive used a 5/64" regular drill bit in a drill set on low speed
tom
Don’t use a 5/64" (don’t ask me how I know, either). Use a #50 or a 1/16".
I would be cautious of using either to large or to small of a tap drill. If the hole is undersized the curling chip can clog the tap flutes and could cause the tap to break, this is one of the leading cause of broken taps. In plastic we can get away with it, with metal and especialy brass this creates more headaches then its worth…LOL been there don that.
Drilling oversized holes of course lessens the thread holding power. is easy to strip out sometime with only snugging the part. Problem this creates is when one replaces a coupler a year from now, one would forget the hole was tapped oversized and inenvertenly strip it out.
Just my 2 cents,…John