The Craftmans Shop > New from Old
The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
djc:
Since you mention "the chuck" in a singular fashion, is it only one, specific chuck you want to mount on the adaptor?
If so, is there any reason not to modify (increase) the chamfer on the chuck if the peskiness proves to be obstinate?
awemawson:
Thanks for the suggestion - not one I'd considered, however apart from not being able to mount it in reverse and it being hardened steel no reason at all :clap:
I'm hoping such activity will not be needed, but yes this is to mount a specific internally hydraulically operated collet chuck of A2-5 mounting specification on a spindle made for A2-6 devices with the same internally operated hydraulic mechanism.
(most CNC hydraulic chucks use an external hydraulic co-axial cylinder mounted round the spindle bore tube - not this one!)
awemawson:
The postman brought the new 0.4 mm carbide tips this morning - not due until Monday so this is a bonus!
They are TPUN 160304 S6-P40 , so the correct grade of carbide as well as correct tip radius which has made a noticeable difference to the surface finish as well as to the corner radius.
I now need to be brave and mount up the actual adaptor and work on that :bugeye:
mattinker:
It's the kind of thing that if your doing it for yourself is not the same doing it for someone else!
All the best, Matthew
awemawson:
The EN8 billet that I have been testing on had a feature that I'd turned on the opposite end that I'd intended for a final 'to exact size' trial from which I could take precise tool positions using the CNC lathes positioning system to avoid any tool setting errors. So I mounted it up, the first operation being to face the end and face the shoulder to the exact 14.270 mm depth. Initially all went well then another DISASTER - tool dig in and part ripped from the chuck :bugeye:
Initially this greatly puzzled me - I was using very conservative in feeds, but then it dawned on me - this boring bar mounts it's insert with ZERO back clearance behind the cutting edge. Usually there is a good 5 or 7 degree, so as the insert is fed in radially if there is ANY vibration it ends up taking a broader and broader cut. The evidence was there from the last dig in. If you look back to the picture of the damage look how broad the eventual chip was once the tool had dug in :bang:
Now I cannot afford to risk this when turning the actual adaptor - I've invested too many hours in it, so I've decided to change horses mid race. I've found a 32 mm boring bar of suitable length that takes VCMT 1604004 tips with a 35 degree diamond profile mounted to give very adequate clearances so I'll just have to twiddle my thumbs until it arrives.
. . . such is life . . .
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