Simple(?) Milling Question

For a 6mm cutter I'd just drill one hole at the inboard end and machine the rest with a slot drill, but you could chain drill, or even saw out the excess. Good idea to put it on parallels inside the jaws, but put something sacrificial between the job and the parallel, or use wood

Thank you, yes I'll likely go for wood in this instance.

Next question having just looked on Arc's website:

My draw bar is 3/8" Whitworth. For my Mill I have both 6mm & 1/4" Myford type collets that fit into the 2MT spindle.

I could buy a 1/4" cutter and fit it directly into the Myford collet in the spindle, so minimum projection which I do know is what I should aim for.

Or, I could buy a Weldon cutter holder for 1/4" cutter with 3/8" draw bar thread.

OR, should I get the 6mm cutter and fit it in the Myford Collet, and NOT use a Weldon as these only come with

10mm draw bar thread?

Thanks

Chris.

Weldon collets cause runout of the tool. The tool goes into an oversize hole and is pushed to one side. This may not matter so much in large diameter roughing tools but is something to avoid with small tools. I don't know what collets you have but if you want to hold the cutter away from the spindle nose you could get something like an ER11 collet chuck on a 12mm parallel shank and cut the shank to a length that suits your needs. Put this into a 12mm Myford style collet. You could also consider an ER16/MT2 collet chuck. ER collets will hold the 6mm cutter with far less runout than a Weldon holder.

Martin C

I'd go with their Premium cutters so that means having to use 6mm and hold that in your collet

Ok great, thanks very much all, I will give it a go!

Cheers

Chris.

One suggestion, if the part is not yet sized to length, is maybe cut a blind slot, then machine off the end to open the slot?

I am sure your right, Martin, from a purely functional angle, but may as well try to get it as near-enough perfect as possible! I use lathe tools as parallels at times though I believe it's not recommended.

One way to support a work-piece like this under the cut itself, is to use a piece of BMS or aluminium bar as a sacrificial parallel.

Chain-drilling the worst out... Having used a heck of a lot of chain-drilling to chew a two-throw crankshaft out of a foot-long piece of what had been a scrapped railway-wagon axle, I would avoid it as far as possible. Even with filing the worst of the "teeth" down it still presents a lot of horrible, irregular lumps and bumps to the cutter and could even cause it to jam.

On the crankshaft I was using a ripping-cutter along the open, drilled faces; but for cutting a small slot such as on Chris' knurling-tool, or a clevis, I would rather let the cutter do all the work, as then it is fully and smoothly supported through the cut.