As fellow hobbyist builders, I am sure you guys could appreciate how often you just wish you had an M48 x 0.75 tap to build stuff. unfortunately no one on earth makes one. So I decided to take a shot and try to make one. I have no idea how successful I will be, but it can't hurt to try right?
Worst case I have a helical boring operation on my homemade CNC to cut M48 threads regardless, but sometimes I just want to use a tap.
The material I am attempting this with is 4140 steel. It is easily hardenable. and soft enough (and cheap) to try it out and see if I can make a successful prototype.
Here I am turning a chunk down to 1" just as a shaft:
(I have been known to dabble in precision)
Here are a few attempts to cut threads and a 3° taper at the end of the tap. (This is just a scrap piece of the steel)
The idea is once the threads are cut, to mill out slots on the rotary table, but I think I have to do that operation first due to the amount of burs when slot milling:
They are cut every 40° to give me some hella rake angles on the each of the cutting passes
Also milled a 0.375 square end on the back to put in a tap.
Now is where it sits, ready to actually cut the threads and put the chamfer.
Will update as it goes. I would like to cut another one first, before I touch this and ruin all the work that went into those slots.