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| Threading...plunge straight in |
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| winklmj:
So I'm working on a replacment axle for a bicycle hub. Broken: Turning between centers with a ball-bearing center. It gets in the way of angling the compound over typically recommended for thread cutting. So...for the 12x1mm thread I just plunged straight in 2-3thou per pass. It turned out OK I think. Is there anything wrong with doing it that way all the time? Start of new one: |
| doubleboost:
Hi No problem on fine threads It is on heavy threads you need a angled top slide John |
| andyf:
I think one objection to going straight in is that a chip is peeled off by each flank of the tool, both chips try to occupy the same space and wedge up. But it obviously worked for you. A half-way house, with the tool set at right angles to the job can be achieved, if the topslide is set parallel to the bed. Each time the cross slide is advanced to deepen the cut, the topslide is advanced towards the chuck by half the amount by which the cross slide was advanced. That makes the leading flank of the tool do most of the cutting, as with the angled approach. It does need a bit of concentration (for me, anyway) to keep track, and if the cross slide dial is marked up in "reduction in diameter" rather than actual depth of cut, then the top slide advance should be a quarter, not a half, of what the cross slide dial shows. Andy |
| AdeV:
I've always threaded straight in, usually because I've started before I remember you're supposed to set the cross-slide over... The main thing is to take ever shallower cuts, as you approach the final dimensions; and I mean 0.001" or less; the amount of material removed even on such a shallow cut is quite remarkable, as you're approaching the thread's depth. If you go too deep on the final cuts, you'll break your cutter. DAMHIKT. |
| arnoldb:
Mike, there's nothing wrong with plunging straight in; just take smaller cuts as the groove deepens. I've cut from 0.5mm pitch trough to 8tpi ACME form like this; my lathe's topslide can't set over enough to use the set-over method. Andy's suggestion is good as well - but the 1/2 feed method on the parallel top slide is only correct for metric and US threads - for Whitworth you need to feed less with the topslide. :beer:, Arnold |
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