The Craftmans Shop > New from Old
The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
awemawson:
The replacement 35 degree diamond insert boring bar has arrived so I did a test cut on the poor old EN8 blank that's been ripped out of the chuck a couple of times by the previous bar.
I turned the blank to the major diameter and length of the taper, then marker blued the parallel blank.
The program progressively forms the taper, reducing diameter by 25 microns each pass. As the taper forms the blue area decreases showing progress. In the final part it will be very securely bolted to the spindle allowing me to make test fits at stages without disturbing it. Here the blank is only in a manual 3 jaw and the weight of the collet chuck would undoubtedly move it in the jaws.
The finish with these tips is not as good as the previous one being slightly 'torn' so I need to experiment with speeds and feeds again.
Sea.dog:
Might it not have bee easier to grind some relief on the previous insert? OK, you sacrifice an insert, but you get the job done and with a better finish.
mattinker:
--- Quote from: Sea.dog on June 30, 2021, 06:49:25 AM ---Might it not have bee easier to grind some relief on the previous insert? OK, you sacrifice an insert, but you get the job done and with a better finish.
--- End quote ---
Inserts are sacrificial by nature.........................
awemawson:
I did consider that Graham, in fact I have two diamond disks sitting on my desk awaiting 3D printed centre adaptors to go on my Clarkson T&C grinder spindle but in the end I decided that the advantage of being able to make an undercut if needed, and the advantage of being able to swap inserts on the fly and remain consistent was worth having.
I've just re-run it with the feeds somewhat reduced and the finish is very acceptable. It'll all change again when I mount the adaptor, as that's EN19T not EN8 !
awemawson:
At long last the taper on the adapter is DONE
This afternoon I mounted up the part finished adapter and crept up on the final size. I may still have to do a bit of adjustment but it's pretty well bang on with the rear flange and the taper closing simultaneously. I may have to trim a tiddly bit off the flange to make sure the mounting bolts pull the taper home for the last tiny bit - not sure.
I used a 'chuck catcher' (just a bit of gas pipe pushed up the spout) to save my toes, and it worked quite well :thumbup:
A slightly stressful operation with people bursting into the workshop at just the wrong moment but I got there in the end :bang:
. . . enough for today . . . . I still need to check concentricity and check the hydraulic side of things but that's for tomorrow
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