Tools for turning in the mill

[Tom DaviesParticipant @tomdavies31655]

[Tom DaviesParticipant @tomdavies31655]

 

I have a Chinese 6040 CNC router which I use for Aluminium, brass, Sterling silver, wood, and plastic. It is rigid enough to do 0.5mm depth cuts in brass/aluminium with 1/8" end mill (maybe it can do more — I haven't tried to push it further.

I'd like to try turning some 1/8" (and later try 1/4" ) brass rod. The parameters would be:

– spindle speed about 10,000 RPM — my spindle doesn't have much torque at low speeds.

– 40mm long brass rod, 1/8" diameter, being turned down to minimum 2mm diameter.

– The rod would be held in an ER11 collet, unsupported at the other end.

I'm confident that I can write the necessary g-code, but I'm not sure about tooling, as I have no lathe experience at all.

I'm planning to hold a tool in a vise clamped to the bed of the router.

Note that I *don't* have a grinder, so I will need to buy pre-made turning tools.

Should I buy something like this: http://www.ebay.com.au/itm/8pcs-High-Speed-Steel-Turning-Tool-Set-/301954687492?var=&hash=item464de6e204:m:mIA3Gv-breAusP4T3pklhxg ?

Thanks for any advice.

Tom

 

Edited By Tom Davies on 04/07/2016 02:47:30

[VicParticipant @vic]

Interesting idea. My first thoughts were that set looks pretty good but you'll still need to touch up the tools on a grinder at point. In practice though you could get away with using a slip stone to put an edge back for quite a while.I think the best answer though is to try and find someone local who can grind a single HSS tool for you as those linked may not have the best profile for brass and plastics. It would be a shame to buy a whole set like that and find it doesn't work very well. I'm sure others must have come across this before though so await further responses.

[JasonBModerator @jasonb]

Your biggest problem will not be the tools but the amount of work sticking out of the collet, this would be far more than normal on a lathe unless tailstock support was used. Your rod will simply touch the tool and then get bent sideways and I don't mean deflet but bend and start whipping around. I have seen turning done on teh mill but with a combination of slower spindle, shorter/thicker work.

If you want to tru shorter lengths then just get a 4mm HSS tool bit and grind it to suit as you will probably want to set the geometry differently to what the ready ground ones come as.

[Tom DaviesParticipant @tomdavies31655]

Thanks Jason — what's a reasonable ratio between the thickness of the stock and the distance between the collet and the point where the tool is applied?

[Michael GilliganParticipant @michaelgilligan61133]

Tom,

To avoid the deflection problems … It may be worth adapting the 'Rose Bit' [ by any other name ] as discussed on this previous thread.

MichaelG.

[JasonBModerator @jasonb]

About 4 to 5 times the diameter on something small like that to start with and then see if you can push it further. It is possible to do your 40mm long cut in stages my doing the first 10mm with say 12mm sticking out of the collet, then pull out another 10mm and machine that, there is a slight risk of a small step with each resetting though.

As Michael says something like the rose bit , "box tool" or "running down tool" may work as that can be made to guide the 1/8" diameter before the cutter and then have a smaller dia support hole for the 2mm dia if needed

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