Two bowls from one blank?

[Rodpr]

I have a few big bowl blanks from the trunk of an elm tree which had to be felled after succumbing to Dutch Elm disease. These are from half logs and some will be turned into 10" bowls which will be nearly 5" deep - a good size for a salad bowl- but I will use some to make two 10" bowls, one about 3" deep and one about 2". For one of these I cut the 2" slice off with the chainsaw but this obviously has a big kerf and loses some of the thickness.

It occurred to me that I might be able to divide a full depth blank while it is on the lathe but, instead of going straight in with a parting tool I could go in at a bit of an angle so that I could keep a bit more depth in the 'faceplate side' bowl. A bit like coring but cutting from the side rather than from the face (and without the expensive coring set up).

I was able to cut about 2/3 of the way in using a straight parting tool but then things started to get a bit snatchy as the cut was quite a way away from the toolrest.

I gave up at this point and cut off the 'faceplate side' piece with a saw, so I didn't save any more than if I had gone straight in with the parting tool, but I wonder if anyone has tried doing this and found a better way.

Is it possible (and safe) to cut off a cone shaped section from a deep blank, so that there is a bit of extra thickness with which to make a tenon on the cut off piece?

The pictures below show what I was trying to do and the bowls I ended up with. This is very green wood (cut down just a couple of days earlier) so the bowls will be turned again when they have dried out.

 

[v8 Fossil]

I saw a video recently with a curved chisel or whatever it is called which was very similar to this. Bowl saver.

 

[Rodpr]

But this produces a set of concentric bowls. What I am after is a way to take equal diameter slices off a blank but with a more conical rather than flat, cylindrical, face.

 

[Sean Hellman]

Turners on a human powered lathe have been doing this for centuries. The bowl lathe is used with hook tools mainly forged by the turner themselves and it has been known to get up to 5 bowls from one blank. Look up Owen Thomas and Robin Wood who are masters of this way of turning, from one 10 inch blank defiantly 2 bowls and even three.

 

[Inspector]

You should look into the McNaughton Centre Saver system. It has a straight chisel and progressively more curved chisels to cut everything from cones to half spherical shapes. It would allow you to part off the back of a bowl to get a piece suitable for a picture frame or what ever. You could also cut a bunch of cones from a longish blank. It is the most versatile coring system but takes a little knack to use. You have to go against your urge to hold the handle down and lift up on it instead.

Pete

 

[Rodpr]

Turners on a human powered lathe have been doing this for centuries. The bowl lathe is used with hook tools mainly forged by the turner themselves and it has been known to get up to 5 bowls from one blank. Look up Owen Thomas and Robin Wood who are masters of this way of turning, from one 10 inch blank defiantly 2 bowls and even three.

I really like Robin Wood's work on the pole lathe and those hook tools look fierce but again this is cutting concentric bowls from the face. Something I may have a go at in future but I thought angled 'slices' off a deep bowl blank might be simpler to begin with!

 

[Rodpr]

You should look into the McNaughton Centre Saver system. It has a straight chisel and progressively more curved chisels to cut everything from cones to half spherical shapes. It would allow you to part off the back of a bowl to get a piece suitable for a picture frame or what ever. You could also cut a bunch of cones from a longish blank. It is the most versatile coring system but takes a little knack to use. You have to go against your urge to hold the handle down and lift up on it instead.

Pete

Hi Pete,

I found this video of cutting four 2" platter blanks from an 18" diameter 9" deep blank using the McNaughton Centre Saver but here these are cut straight in rather than angled towards the drive, making 2" cylinders rather than more conical pieces.

https://www.google.com/search?q=McN...#fpstate=ive&vld=cid:5f2381ef,vid:d73p9RzFgec
I guess you could use the system to cut in at an angle though and the tool is very well supported. One obvious problem with cutting in at an angle is that you would not be able to finish the cut with a saw. You would have to keep going until the outer piece could be broken free!

 

[Orraloon]

I was lucky enough to find a secondhand McNaughton set about 10 years ago. There is only so much you can do with the strait cutter and I seldom use it. It will get further in than a parting tool however as the tool is captured and has way more leverage. The curved tools save so much more wood. I noticed that the pole lathe guy also used curved tools with huge long handles to overcome the leverage issue. Most coring systems and deep hollowing systems have some way to capture the tool to support against that leverage. With a hand supported tool you will only manage modest sized bowls. I was having a look and found this video by Richard Raffan.
Richard Raffan on simple bowl coring - YouTube
Regards
John

 

[Rodpr]

Thanks John. That tool is a bit of a beast! I would have assumed one would flip the blank round first, after making a big tenon on it. Then you could come in with the tool as with the coring systems. I guess it makes sense to keep the inside on the faceplate so you can put a tenon on it but I noticed that Richard cut the outside off before making a tenon so finishing the outer bowl will be a bit trickier!

 

[mindthatwhatouch]

Not sure these are still available, but it's basically a heavy duty straight parting tool. Is this what you are trying to achieve?

 

[Rodpr]

Hi M, yes but no but ...
I was wanting to keep the full diameter of the blank by taking an angled slice out of it. I have tried to draw what I mean. By cutting in along B-C I should be able to take a full diameter piece out and make a slightly deeper bowl than if I just cut straight in A-A.

The conventional coring process takes out concentric pieces, leaving the outer bowl at full depth (as shown on right of my sketch). I can see that this makes sense bu it is not what I am trying to do!

 

[Rodpr]

I have just had another go. A very wet piece of elm (from a tree cut down just 5 days ago). 5" felt too deep for an 8 1/2" bowl so I cut off 2" but at an angle. Just using regular parting tool and it did get a bit grabby again but I got in far enough to be able to knock the pieces apart with a mallet. I ended up with an 8 1/2" X 3" dish (a whole extra inch of depth!!) and a 7 3/4" X 3" bowl. This is all I was asking for so I am pleased!

 

[Duncan A]

Interesting, if I've got this right, you're going in from the side rather than the front end.
That being the case, the McNaughton could do the same thing, with the added benefit of producing shaped bowls.
I seem to recall a video of a traditional woodturner in China producing multiple bowls from a small log (end grain bowls) using a similar technique and very basic equipment
Duncan

 

[Rodpr]

Hi Duncan, today I decided to keep a full depth bowl so I cored out some heartwood from the face in the traditional way. This was quite doable with a bog-standard parting tool and, as I can't turn anything much bigger on my little Jet lathe, I can't see myself investing in beefier gear for a while. I have attached a short video to show how well my little Jet lathe managed with a big, wet lump of elm. No vibration at all! And this is about as big as I can get on it (I had to chisel some corners off before it could turn).