bowl lathe made from cleft wood (picture heavy)

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bowl lathe made from cleft wood (picture heavy)

Postby Nicola Wood » Sat Jun 07, 2008 9:33 pm

I just found these pictures from one of Robin's courses in Sweden - the first one he taught there back in 2004 I think. It's not exactly a comprehensive tutorial, but enough for you to see how they were made I think:

The basic bed is half a big log with four legs in:
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Cutting the slot is quickest with a chainsaw, but not to be attempted unless you're very skilled!
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Squaring it up a bit on top & underneath:
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Offering up a squared up piece for one of the poppets:
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Finished poppets:
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I think that shows the tool rest arrangement a bit better:
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Ola making a bowl on his new lathe:
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Some bowls made by course members:
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BBQ Swedish style at the end of the course:
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Lovely place, lovely people, happy memories :D
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Bowl lathe making

Postby Robin Fawcett » Tue Jun 10, 2008 12:15 am

That's a lovely sequence of photo's . . .

I'm really surprised there's been no other replies to this post.

Perhaps everyone's dead after cutting off their legs after trying to balance on the bed to cut out the slot ?!
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Postby Spokeshave » Tue Jun 10, 2008 3:36 am

Thanks Nicola. Yet another example of the endless nuances in the form of lathes.

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Postby robin wood » Tue Jun 10, 2008 7:26 am

Spokeshave wrote:Thanks Nicola. Yet another example of the endless nuances in the form of lathes.

- Dale


Dale I love your sig line, can you give me a reference for the Leonardo quote, where did you come accross it?
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Re: Bowl lathe making

Postby Nicola Wood » Tue Jun 10, 2008 8:09 am

Robin Fawcett wrote:That's a lovely sequence of photo's . . .

I'm really surprised there's been no other replies to this post.

Perhaps everyone's dead after cutting off their legs after trying to balance on the bed to cut out the slot ?!

or perhaps just legless :lol:

joking aside, I think the recommended solution is to drill some big holes through and chop out in between with a chisel!
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Postby Tom B » Tue Jun 10, 2008 8:49 am

I think the recommended solution is to drill some big holes through and chop out in between with a chisel!


That could take some time!

Is there much of a shrinkage problem if you build these in green wood?

I realy enjoy sets of pictures like this- very inspiring! Thanks for posting them!

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Postby robin wood » Tue Jun 10, 2008 9:29 am

Tom B wrote:
I think the recommended solution is to drill some big holes through and chop out in between with a chisel!


That could take some time!

Is there much of a shrinkage problem if you build these in green wood?

I realy enjoy sets of pictures like this- very inspiring! Thanks for posting them!

Tom


Making the groove with a big auger (same as the one used for the legs and choping out with an axe is not such a chore, I reckon about an hours work but on the courses I had 8 to do so use a chainsaw.

Shrinkage with green wood is only ever a problem if you do not understand how the wood shrinks in the 3 different planes and make your design accordingly, frame furniture, timber framed houses and ladder back chairs all show designs that use green or part seasoned wood and skillful joints that work as the wood dries. This lathe design works too. I have built probably 30 of them over the last 10 years and the design has gradually evolved.
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Postby Mark Allery » Tue Jun 10, 2008 11:39 am

Nicola & Robin,

many thanks for posting this sequence of pictures - and great timing as I was just about to build my third lathe and considering doing something along these lines.

I also have access to a lot of birch and am delighted to see that the lathes were made from it. Did you feel that there was any disadvantage to using Birch? Once seasoned it has the same static strength as oak (ie its a very hard wood) but with much less density (ie weight). Of course it doesn't have the same dynamic strength and won't withstand shocks and bending as well - but I guess thats not a problem in this useage?

I don't think I will try Robin's chainsaw technique for the bed - although it answers my question about the strength and stability of the legs! I will prop the bed up on its end and save my back! I have a small saw that I reserve for cutting mortices and carving, 91vg chain and small narrow tipped bar - although it has a nose sprocket its not too bad and should do this job well.

One of my old landrovers has just had a spring change, so I have the components for the ironwork as well, using the old spring bolts and shackles. The springs have gone to a friend who is a blacksmith for conversion to froes, billhooks and drawknives.

How did you secure the centres in the poppets?

Very inspiring, its just jumped up my priority list, will try to post on how I get on

cheers,

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Postby robin wood » Tue Jun 10, 2008 3:44 pm

Mark Allery wrote:Nicola & Robin,

many thanks for posting this sequence of pictures - and great timing as I was just about to build my third lathe and considering doing something along these lines.

I also have access to a lot of birch and am delighted to see that the lathes were made from it. Did you feel that there was any disadvantage to using Birch? Once seasoned it has the same static strength as oak (ie its a very hard wood) but with much less density (ie weight). Of course it doesn't have the same dynamic strength and won't withstand shocks and bending as well - but I guess thats not a problem in this useage?

I don't think I will try Robin's chainsaw technique for the bed - although it answers my question about the strength and stability of the legs! I will prop the bed up on its end and save my back! I have a small saw that I reserve for cutting mortices and carving, 91vg chain and small narrow tipped bar - although it has a nose sprocket its not too bad and should do this job well.

One of my old landrovers has just had a spring change, so I have the components for the ironwork as well, using the old spring bolts and shackles. The springs have gone to a friend who is a blacksmith for conversion to froes, billhooks and drawknives.

How did you secure the centres in the poppets?

Very inspiring, its just jumped up my priority list, will try to post on how I get on

cheers,

Mark


I think Birch would be an ideal timber for a lathe if you will keep it dry or only subject it to an occasional wet demo day. If it will live outdoors I would probably choose something more durable, birch rots fast if damp.

Centres into poppets...I just drill a hole that is a tight interference fit for them and bang them in using a tough knotty bit of wood between hammer and centre point. If they are sunk well in say 3" they don't work loose. If you didn't have a drill that gave that tight fit I would use araldite / car body filler type glue.
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pole lathe from cleft wood

Postby Steve Martin » Wed Jun 11, 2008 5:12 am

Just to see if I have this right, if all the parts are made from the same log and completed within a reasonable time frame, say a week, wouldn't all the parts shrink at the same rate and over the same time period? Thus making any shrinkage a moot point? If the legs were made from a different wood, say cedar or white oak, they should be drier than the wood of the bed so that as the bed dries it will tighten up on the legs, holding them in place, like the stretchers in a chair leg, unless ,of course, you want them to be removable to transport. Then you would want to adjust the size of the holes or the legs, so the drying won't tighten up on them, right?
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Postby Nicola Wood » Wed Jun 11, 2008 9:35 am

A very quick bit of back to basics for anyone reading this who is new to green wood - wood shrinks as it dries, but this shrinkage is not even; tangential shrinkage (around the grain) is far greater than radial shrinkage (across the grain) - shrinkage along the length of the log is negligible.
Image
The stress caused by this is greatest at the centre of the log (the pith) and if left in the round often causes star-shaped splits from the pith outwards. You can relieve some of this tension by splitting the log in half - as a result it will shrink down more at the sides than the middle. It is still advisable to axe some wood away from the split face as the pith may still split. Different timbers shrink at different rates and you will find some more stable than others.

So the lathe bed is going to dip down a little at the edges and the poppits will curve a little too, but this is not important. If they get looser in the slot you just bang the wedges in further and if they start to bind where you want to slide them then shave a bit more off them.

The legs will oval and the holes they go in will distort but the top ends of the legs are tapered where they fit into the bed so if they loosen as they dry you just need to whack them in a bit further. The sheer weight of the upper structure pressing down on them should keep the whole structure stable.

More art than engineering, but it works. Robin has a lathe like this which he takes out to shows. He's taken it apart and put it back together many, many times over the years and it does a fine job!
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Re: bowl lathe made from cleft wood (picture heavy)

Postby Rob. N » Tue Dec 02, 2008 12:39 pm

How Did you get the angles for the legs? or is it best guess.
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Re: bowl lathe made from cleft wood (picture heavy)

Postby gavin » Tue Dec 02, 2008 7:53 pm

Rob. N wrote:How Did you get the angles for the legs? or is it best guess.

I do mine at 22 degrees or 25 degrees to the horizontal. I found when I did them at a more open say 30 degrees, then the legs had too much give in them. My auger is 38 mm i.e. one and half inches, and I bore it into milled plank approx 80 mm thick.
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Robin's pictures indicate a flatter leg angle, perhaps 30 or 32 degrees. I suspect that works for him because the holes are deeper into a thicker lathe-bed. I don't know what his hole diameter is.
Last edited by gavin on Tue Dec 02, 2008 10:20 pm, edited 1 time in total.
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Re: bowl lathe made from cleft wood (picture heavy)

Postby robin wood » Tue Dec 02, 2008 8:24 pm

Rob. N wrote:How Did you get the angles for the legs? or is it best guess.


I judge by eye, it is important they splay side to side as well as back to front.
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Re: bowl lathe made from cleft wood (picture heavy)

Postby gavin » Tue Dec 02, 2008 9:31 pm

Rob. N wrote:How Did you get the angles for the legs? or is it best guess.


Pictures being better than words, here is how I do it:

  • When looking from the top i.e. plan view you want them splayed 45 degrees. I placed a triangle template on the underside of the lathe bed...Image
  • to create a line at 45 degrees to the slotImage
  • now set your bevel-gauge to 22 degrees to the vertical or 112 degrees to horizontal...Image
  • and bore your hole...
    Image

I drill this from the underside because the auger's entry hole is always neat and clear. If I drill from the top, the exit hole often has an ear of wood left. To chip this off is tedious. But bashing the leg up from the bottom will quickly shatter that ear of wood off.

If you drill from the top, you'll need to reverse the angles I have shown. And if you use the half-log method Robin used in Sweden it would be awkward to use a bevel gauge on the rounded bottom, so you would need to place that gauge on the top. If you are happy drilling by eye from the bottom, that would have to be quicker. But it is annoying if you discover your eye was not accurate. :oops: - as I discovered mine was not!
( These images are from my DVD "How to Turn a bowl - with your leg", available in Trader's Corner on this board)
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