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Jacob

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Turning 80 of these bobbins. Unfamiliar work for me but a good exercise in getting everything sorted, which is working well so far.
Except for my live centre. Just a plain pointed one.
I start the turning between centres by truing up and marking out a 48" x 3" square piece of beech (corners taken off by bandsaw). Then pick out the marks with a parting tool, then take out some of the waste on each of the 8 bobbins, but not too much or it'd be too bendy, then finish off just the tail stock end one and saw it off, and repeat.
Works OK except every now and then the workpiece makes a bid for freedom and comes off the live centre. :shock: No surprise really it's a heavy bit of wood with just 2 or 3 mm depth of point holding it. Headstock end firmly held in Sorby chuck.
So is there a live centre which would combine with a pin to locate into a predrilled centre hole say 10mm deep and 8 to 10mm dia? Or other solution? Couldn't see one in the catalogues.
Then if it came loose it'd rattle about and give warning instead of leaping off.
4bobbins.JPG
 

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Jacob

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Right ho ta. I hadn't thought of looking at hole boring kit. I'm just doing short 6" holes which is no prob with a chuck in the tail stock and a 10mm twist bit.
Next prob is it's a No 1 morse taper but I'll keep looking.
 

alexalexander

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Could you use a hollow live centre - the sort used when using an auger to drill deep holes - but instead of running an auger through it, you would have a cylinder which would insert into your 10mm hole. You'd have to get it to stay put somehow.
 

Trevanion

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I was more on about using the centre with the pin in it to centre your work rather than using it to bore out the bobbins, but I suppose that would work also.
 

Phil Pascoe

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Jacob":3ckkdplh said:
Right ho ta. I hadn't thought of looking at hole boring kit. I'm just doing short 6" holes which is no prob with a chuck in the tail stock and a 10mm twist bit.
Next prob is it's a No 1 morse taper but I'll keep looking.
If that sorts your problem you can get it in MT2 as well.
 

monkeybiter

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I've turned custom profiled caps that push fit on the live part of my live centre. If the shape of yours would support something like that it could be a solution.
 

Rorschach

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Buy a centre drill and drill a deeper hole so there is more purchase on the live centre.
 

Jacob

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Yes. It dawned on me in the night! Obvious really make a deeper countersunk hole so the centre is better located. Off to do it soon as I've had a cup of tea.
I'll look at hole boring kit though, but I try to avoid buying stuff as a rule.
 

Jacob

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phil.p":1mrla7d8 said:
Rorschach":1mrla7d8 said:
Buy a centre drill and drill a deeper hole so there is more purchase on the live centre.
The way I read that he already had a 10mm hole.
No the hole through bobbin is the last thing. Hole boring kit could be good if I do this again - pre drill the hole all the way through the unfinished bobbin at the end of the workpiece so that when sawn off there's the start of a hole still there nice and central
 

Rorschach

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phil.p":19goic3f said:
Rorschach":19goic3f said:
Buy a centre drill and drill a deeper hole so there is more purchase on the live centre.
The way I read that he already had a 10mm hole.
As confirmed in a later message I didn't read it that way, I thought the hole was a possible option. Straight sided holes being a bad choice for live centres compared to a proper 60deg countersink.
 

Mark Hancock

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If I've understood your process right you are drilling the hole after turning the bobbin? It's usually recommended to drill the hole first for anything that has a hole running down it e.g. light pull, lamp etc. then mount on the lathe using the holes. That way everything will be concentric to the hole. With a bobbin it's easy to mount with the pointy live centre in one hole and a counterbore drive in the other. If you don't have a counterbore drive just turn up a dowel with backstop and hold in the headstock in a chuck.
 

Jacob

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Mark Hancock":2np32xmr said:
If I've understood your process right you are drilling the hole after turning the bobbin? It's usually recommended to drill the hole first for anything that has a hole running down it e.g. light pull, lamp etc. then mount on the lathe using the holes. That way everything will be concentric to the hole. With a bobbin it's easy to mount with the pointy live centre in one hole and a counterbore drive in the other. If you don't have a counterbore drive just turn up a dowel with backstop and hold in the headstock in a chuck.
Yes. Except I haven't got anything long enough to drill a 6" hole through in one, but am looking at the options. The other prob is that I'm trying to turn as much of the job as I can on the max length of workpiece to avoid multiple handling. 7no 6" bobbins on a 43" workpiece seems OK. Could go longer but it gets cumbersome.
One way or another I'm finding out how to do it!
 

Jacob

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First batch done. A bit head-down brain-off but OK.
Could not use hole boring kit even if I had one as these bobbins needed a 10mm hole to fit the clients rack but my tailstock bore is less. Used normal twist bit in a chuck instead. Winding it in to start then sliding whole tailstock unit to continue
I've done 30. The next lot will be a piece of water!
I think the roughing out on long workpiece is effective but then cut it up and finish each one separately.
Bit of a learning curve!
Thanks for suggestions.
 

Rorschach

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If you drill freehand on the lathe you only need a 3" drill to drill a 6" hole (that's 3" cutting length of course).
 

Jacob

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Rorschach":2s35j7ft said:
If you drill freehand on the lathe you only need a 3" drill to drill a 6" hole (that's 3" cutting length of course).
Yes got that. Only one went a bit off centre.
 

Rorschach

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What method are you using for the drilling? I never go off centre when freehand drilling.
 
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