Some interesting parts out of 42CrMo4, a centrifugal clutch and a starter adaper for a RC helicopter model.
Pictures of manufacturing those parts:
The starter adapter has a 6mm internal hex, which was rotary broached.
The rest is pretty standard turning work.
The clutch has a 2mm corner radius – Such a tool could be ground on the D-Bit grinder. But sometimes its easier to take a piece of round carbide the right diameter and silversolder it verticaly to a shank (With 2..3° of clearance)
With this tool the radius could then be turned:
Parting off, 50mm diameter with a 1,6mm HSS parting blade:
Setup for the second side, holding it in a 5C collet. Using my universal micrometer with a thin anvil to measure the thickness of the flange.
A small detail – The starter adapter has a large 90° countersink in it, you could do that just with a standard countersink, but I didn’t want to take any chances of chattering, so I used a carbide-chamfering tool to form that countersink. This is a safe way to get a clean countersink that’s true running and has a good surface finish.
Next are some milling operations. The starter adapter is pretty fragile, so I didn’t want to put it directly in the three jaw chuck.
Instead I made a small fixture and used a stud and nut to hold the adapter down for machining.
The holes and corner radii are drilled by coordinates, the remaining material is removed using the rotary table.
The clutch has also some holes drilled into it and is slit – At first I wanted to do that with a 2mm slitting saw, but the remaining material is very thin and I was worried that the part might get destroyed. So I played safe and did the slits with a long 2mm carbide endmill.
The endmill was ran at 3000rpm, 0,2DOC and 300mm/min feed, that way it went quite fast to cut those two slots.