machineing radius edges

[m_c]

Radius cutter, however 8mm may be a bit big for anything but a reasonable size machine with a relatively slow spindle.
I've just checked the first cutter I found (arc euro trade), and an 8mm radius cutter is 24mm OD, with 8mm centre, and a 16mm shank, so a failry substantial machine would be needed.

Removing the bulk of material using a normal endmill and several passes would mean minimal cutting for a final finishing cutting pass.

Other option would depend on how good a radius you want. You could probably get a reasonably OK finish using a ball end mill and multiple passes.

[magicniner]

But how do you transition from one size to the other with a radius cutter?
I suppose you could clean the transition up with a file?

[m_c]

But how do you transition from one size to the other with a radius cutter?
I suppose you could clean the transition up with a file?

He only asked about the radius edges, not the stepped bit ;-)

It all depends on the quality of finish required.

[magicniner]

[charlieuk]

cool wasn't aware you could get something like that for metal, I was searching for round over bits but only found wood type ones. I may be able to put that in my x2 mini mill just. I can get away with not having the step for the prototype . I guess the best way to get that would be on a 4 axis machine, if anyone thinks they can cnc this if its not going to cost a fortune just drop me a pm

many thanks

[Neale]

Are the radiused edges purely cosmetic, or is sizing critical? You could start with a round bar chosen to give about the right radius on the corners and then machine flats to form the faces? Not sure how you would then handle the stepped-down section; personally I would probably stick the bar in a 4-jaw chuck and turn the corner off on a lathe. CNC isn't the only answer! Be interested to hear how you solve it in the end.

[charlieuk]

its not 100% critical I'm making another part that this will slide into, I was wondering about getting a 4 jaw chuck for my lathe and doing exactly that but I drew it up and it just didn't look nice at all so left that idea. I had also considered trying to find some 8 sided hex. bar but that doesn't seam to be easily available. I really must get on the case of building a better cnc to do this sort of work although it looks like that will now have to include a 4th axis!