If you use a flycutter rather than a milling cutter you can get the chamfer cut at the same time with a suitably shaped cutter. I'm a one key man myself.

Using a file would be my choice but if you want to mill the chamfers you have stated the method I would use in your post, just do the 4 flats with the flutes and then mount the block at 45 deg and do the chamfers using the end of the cutter. If using a machine with any backlash get the tool positioned so you are not climb milling.

Emgee

The original was probably made with a tool like this. I turned down the shank to Ø20mm to suit smaller collets.

Martin C

Since you mention holding the work in a square collet block withe the barstock horizontal, why not re-think the relative position of the job to the cutter. I would use the side of an endmill to cut the flats on the 'side' of the work rather than using the endface of the cutter.

The cylindrical shape of the cutter will produce a radius rather than a chamfer, its arguably better from a strength POV but I prefer the appearance anyway.

Ian P

Too late to edit my last post, but confess I replied without properly reading Bazyle's reply which had already covered what I suggested.

Ian P

Not sure I’d bother myself but you could cut the flats to size first then go round again putting in a radius with a bull nose end mill if you have one. Quite quick and easy and should look ok?

Edit: Reprofiling the corner of an end mill is not a bad idea if you have some spares. They can come in handy from time to time and I usually do this to old (but still sharp) imperial cutters I’m less likely to use. Grinding a tool from scratch specifically for only four cuts makes somewhat less sense.

Edited By Vic on 03/11/2020 15:32:23

Definitely bevelled end mill or slot drill. They produce exceptionally smoothe surfaces and take far longer to blunt.

Also you can mill chuck key ends.

regards Martin

I imagine you could get a sufficiently similar effect shaping the step by passing a suitably angled cutter across the edge in a reciprocating motion.

Hack it out roughly with saw'n file then do the, slow, reciprocating bit on the machine to get them all exactly the same.

Hafta get it right.

If you are the sort of person who likes such things anything more than a thou or two or degree or two error will scream at you every time you pick it up.

Clive

1600 rpm is way too fast for a 16mm (5/8&quot diameter cutter. It will be losing its cutting edge as you go at that speed, which is why its getting harder going.

BAsic formula for HSS cutter with mild steel material is RPM = 400/diameter in inches. So try more like 600rpm or even a bit slower for silver steel.

You should be able to do it nearly in one cut. Or one roughing cut then a final finishing cut.

For a start the 2-flure cutter is not ideal for edge profiling work, 4-flute would be much better or even 3-flute as a half way measure.

Say a moderate 20m/min cutting speed for silver steel with a 12mm cutter 526rpm but you could go up or down from that. Probably opt for your 325rpm as there will be a lot of cutter engagement at the end of the cut which can cause chatter.

Metric formula is cutting speed divided by diameter ( in meters) x Pi so 20 / ( 0.012 x 3.142)

I'd go with two passes 1mm each and then as the cut gets longer height wise go for 0.5mm for the last two passes.

Edited By JasonB on 04/11/2020 13:05:04