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| Boring Deep But Small Holes |
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| awemawson:
Background: I need to bore a set of 32mm thick soft jaws to accept 10mm copper bar. (This is on my Traub CNC lathe) So not only is the finished hole fairly deep relative to it's diameter, it'll be an interrupted cut, and not only that, but with the jaw clamping ring in place fitted close access to the jaws is limited so the overhang needs to be getting on for 60 mm I'm tempted to just run a long series 10mm end mill through them but it seems a tad crude, and although hole size isn't needed to be accurate to much more than + /- 10 thou concentricity is important. |
| Fergus OMore:
No doubt that there will be other replies but the classic way is to pull the tailstock poppet out and replace it with a piece of round with a 10mm hole bored right through. This is the steady- used by ALL bagpipe makers. The tool is nothing but a piece of 10mm round silver steel with a D Bit sufficient to drill the full depth and a little bit. Temper the end of D Bit- and simply peck away with the tailstock steady right up to the work. I've done holes 13" long and 3mm diameter in African blackwood and Lignum vitae this way. The trick is to clear continually- or it will all wander or seize. OK? Norman |
| awemawson:
An interesting approach Norman, thank you. No tail stock as such on this lathe, it has an 'opposing spindle' driven by a tiny little 12 kW motor :bugeye: but I could certainly program it to peck away with a D bit.. Not sure what the effect of the interrupted cut would be though. |
| Fergus OMore:
32mm deep isn't a lot. Of course you could just bore it- jaw by jaw. Or - wait for it put a piece of round in it- with a split in it- and then drill a 10 millie hole- and nip the rod. A sort of like a split die? Then you have your soft jaws unmachined- eh? Well, he did ask :lol: Cheers Norman |
| awemawson:
Thanks for the suggestion Norman, but the split collar won't work in this situation. This is 'widget production '. The copper bar is in 1 meter lengths, is griped in the soft jaws, part turned in main spindle, opposing spindle advances grips the part which is still attached to the bar. Main spindle releases it's grip and bar and part are pulled out 45 mm. Main spindle grips again, both spindles spin up to speed in synchronism, the part is parted off. Opposing spindle withdraws and second operation is performed on its left hand end (drill and tap).. The parts catcher comes out, opposing spindle stops, parts ejector pushes part out as flushing coolant washes the collet for next time. The the whole cycle repeats until the bar is all used. Nb main spindle has a sleeve reducing it to 10.2 mm to prevent bar whip. |
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