rotating centers

discussion of the niceties of turning on a bow, bungee or pole lathe.

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rotating centers

Postby roosstoi » Tue Mar 13, 2012 7:49 pm

It seems to me that every lathes picture show fixed centers. I know rotating centers may cause damage on the tools, but (I have to admit I use rotating centers) I had this in mind and up to now never came in touch with the centers. So, is it just a question of style or is/are there reasons I cannot see up to now?

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Re: rotating centers

Postby Bob_Fleet » Tue Mar 13, 2012 8:56 pm

Probably no reason not to use them apart from the cost - cheapest about £18 each.
Fixed one easy but you'd also need to make an adjusting mechanism to hold the other one unless you move the poppet every time.
They also look fairly well engineered and not quite the simple style of a wooden lathe so wouldn't suit re-enactment style lathes.
There are probably a few using them out there.
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Re: rotating centres

Postby roosstoi » Tue Mar 13, 2012 9:52 pm

I first wound the crank through the poppet and then welded a rotating centre on top of it, so I don´t have to move the poppets.
I understand the "re-enactment style" thing, but as a start I built and used my lathe according to
Mike Abbots plans. But, nearly everytime when I was starting to turn and was concentrated on my tools, I forgot to turn the crank from time to time. At least I "woke" up from my concentration when my wooden piece of work flew away.
But already in the beginning I noticed and was sure that this pole lathe theme, or more the green wood crafts, would fascinate me for a long time. So I was looking for a solution and these two centres were worth all the money --- no flying objects any more ;-)
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Re: rotating centers

Postby Bob_Fleet » Tue Mar 13, 2012 10:44 pm

Using fixed centres can wear into the wood but if you were making stuff in earnest they would be on and off in a few minutes so it wouldn't need a rotating centre.
If I'm doing a demo and a piece might be on for ages then a touch of grease is enough.
Probably simplicity and cheapness explains it best.
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Re: rotating centers

Postby gavin » Wed Mar 14, 2012 8:34 am

roosstoi wrote: it just a question of style or is/are there reasons I cannot see up to now?

You ask why you don't see 'live' centres i.e. where the work spins on some ball-race or roller-bearing on the images on this board.

Answer: You don't actually need that level of complexity or engineering expense. If you want to, do it. But ' dead ' centres work fine and are simple to construct. I have only used them on a powered lathe. I don't miss them on pole-lathe, and perhaps they'd help.

I do greenwood work because I wish to raise consciousness amongst others about simpler ways of living. For me, adding complexity such as live rotating centres to any system I exhibit makes that consciousness harder to raise.
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Re: rotating centers

Postby roosstoi » Wed Mar 14, 2012 3:57 pm

I do greenwood work because I wish to raise consciousness amongst others about simpler ways of living. For me, adding complexity such as live rotating centers to any system I exhibit makes that consciousness harder to raise.


Hi Gavin

I agree with your arguments, this is also my point of view of my future living .
My pole lathe is kind of a "prototype" and has to be improved, not technically, but I need other measurements
and I need a much more massive way of construction. (My lathe moves sometimes like an old washing machine)
This can be done with natural wood of bigger size and then I will make a downgrade with my centers.

Btw: is it centers or centres, I thought centres but my spelling check wants it the other way.
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Re: rotating centers

Postby gavin » Thu Mar 15, 2012 10:28 am

roosstoi wrote:[
My pole lathe is kind of a "prototype" and has to be improved, not technically, but I need other measurements
and I need a much more massive way of construction. (My lathe moves sometimes like an old washing machine)
This can be done with natural wood of bigger size and then I will make a downgrade with my centers.

If you have a chainsaw, you can take a log approx 180 cm and put a slot 100 cm in it. This gives a rustic effect. It is cheap and quick.
roosstoi wrote:Btw: is it centers or centres, I thought centres but my spelling check wants it the other way.

American spelling: centers but UK: centres
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Re: rotating centers

Postby jrccaim » Fri Mar 16, 2012 5:46 am

Easy part first. American spelling is "center" and UK/Canadian/Australia/NZ spelling "centre". Over here a rotating center (OK, I use the American spelling. So sue me :) ) is called a "live center" as opposed to the usual static center, AKA "dead center". Live centers are are expensive. This is because they involve a ball bearing somewhere. Or a roller bearing. Both are precision stuff. Hence, expensive. If you are machining steel, there is a point at which a live center will save you a great deal of grief. For wood I find that it is unnecessary. Sure, the dead centers will dig into the wood. They are drill bits. So tighten up the screw. Keep on turning. After a while it is automatic to check end-play on your turning. Apply oil liberally. Much cheaper to buy a bottle of oil than to fit a live center/centre. Any old oil will work and so will wax. But veg oil is cheaper.
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Re: rotating centers

Postby Bob_Fleet » Fri Mar 23, 2012 12:46 pm

jrccaim wrote: Any old oil will work and so will wax. But veg oil is cheaper.
If you use thick grease then you can easily make sure it's there when you need it.
Just bore a vertical hole 3/4 to 1" wide in the top of one of your poppets about 1/2 - 1"" deep. I'm right handed so ..................
Put some grease in and it's always handy.
Just a quick smear with a finger into the starter holes on the workpiece as you put the cord around it.

A little tip though.
Make sure the level is below the top of the poppet or you'll soon discover how often you unknowingly lean on it with your elbow when you drink your tea.

However, if you're production turning rather than demonstrating, the workpiece is hardly on for long enough to merit it.

If you're a re-enactor then I'm sure that Castrol is latin for goose so no problem there then for authenticity. :roll:
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