Woodcut BowlSaver - Limitation?

[bobblezard]

Hi, I am wondering if anyone has experience of using the woodcut bowlsaver? I have recently bought it and set it up carefully, it works well however one limitation is troubling me, I don't seem to be able to save larger diameter bowls 250-300mm from relatively thin blanks of around 80mm thickness.

I knew from the literature that it would only be possible to save one bowl from a blank 80-90mm thick but did not realise that the diameter of this blank would be so limited - I have a lot of stock that is around 400mm x 80mm and there is a lot of hollowing left to do once the bowl has been saved. I was hoping for lots of nice 300mm platter blanks from these.

The main problem is that it is not possible to keep the table and main body of the saver close to the workpiece and that, therefore, the amount of chatter is horrendous as the blade is not supported. Has anyone worked a way round this or explored ways of saving larger diameter but shallow bowls? Maybe I'm just missing something obvious, am trying to push the tool too far or have made a schoolboy error? Thanks

 

[Silverbirch]

There`s at least one video on Youtube on the Woodcut Bowlsaver, which I expect you`re familiar with? If not, it may shed some light on your problem.

Ian

 

[CHJ]

........ Has anyone worked a way round this or explored ways of saving larger diameter but shallow bowls? ........... or have made a schoolboy error?

I'm afraid the latter, as the knives are a fixed radius pivoting about a fixed point you are never going to be able to cut a curve of a greater radius to form a shallower bowl.
With systems such as the McNaughton Centre Savers that use varying radius free tooling running through a toolpost gate it is possible, with a little judicious manipulation and control of the cut clearance to obtain a greater variety of width against depth.

 

[Paul Hannaby]

I have both the woodcut and McNaughton coring systems. The woodcut has less variation with the radius of the cutter but you can manipulate the start position and angle a little to tweak things but there are limits. As you have already found out, witith most coring, it is the depth of the blank that matters more than the diameter.

I'm not sure why you can't get the body of the bowl saver close to the blank unless the surface of the blank is irregular?

 

[bobblezard]

Thanks for the replies, yep I've seen the video on YouTube and the CD that Woodcut provide. I think I'm just going to have to save a smaller bowl and carry on removing the rest of the waste with the gouge.

Paul, I can get the body of the bowlsaver up to the blank initially, it is in positioning the pivot (using the guide template supplied) that I cannot get the pivot lined up and the blade still touching the surface without the body moving away from the blank by around 2 inch.

 

[Paul Hannaby]

Yes, with shallower blanks I guess there will be a gap but bear in mind that the support is designed to give adequate support even when the cutter is fully extended so in effect, you are just starting half way round the cut.

Have you tried increasing the speed for the initial entry cut? that might help even out the chatter. Remember to slow it down again once the cut is established.

 

[bobblezard]

Hi Paul,
Yes I have tried speeding the cut up and slowing it down, the entry cut works well enough - it is further around the cut the the problems arise, I don't think its up to it so I have continued saving smaller bowls for now.
Thanks again

 

[Martin Brown]

My name is Martin Brown and I am part of the team that looks after Woodcut in the UK.

I saw this thread and asked Woodcut for their input. They are a small company who live and breathe their tools, so I thought it a good idea to seek a response.

Here is the reply. Note I am not a woodturner and so have posted this as I received it, and would welcome any comments. If you would like to email Peter at Woodcut directly I can put you in touch.

Our 2 blades have radii of 95 and 125mm.
The ideal size blank to get maximum yield is 350 x 150mm. Maximum yield under normal circumstances is 4 bowls.
The most we have obtained with the aid of the Bowlsaver Laser Guide (and a
little trickery!) with a dry kauri blank is 7 bowls!

What I recommend is as follows:
- Get a BS Laser guide which will show him where the blade is going to cut.
- Put the blade tip up to the bowl and pull the pivot part of the Bowlsaver assembly back. This will eliminate the hang-over and chatter he was experiencing and cut a shallower bowl.
- When he gets towards the maximum depth of cut, stop the lathe, loosen the 2 blade tightening bolts and slide the blade out so that the base is no more than half way out. Re-tighten well before proceeding with the cut with caution.

This should work well for his 300mm wide blank and possibly up to 350mm but 400 would be pushing it.

 

[CHJ]

.....
I saw this thread and asked Woodcut for their input. .......Our 2 blades have radii of 95 and 125mm.
The ideal size blank to get maximum yield is 350 x 150mm. ........

Unfortunately the OP has 80mm thick blanks, hence his limitation:-

..I don't seem to be able to save larger diameter bowls 250-300mm from relatively thin blanks of around 80mm thickness.
..

 

[bobblezard]

Martin,
Thank you very much for your reply, I saw the laser guide when buying but obviously this represents more outlay. I'll consider it and try the methods suggested in future, this will tempt me to set a few of the blanks aside for now.

The next batch of stock will be to the optimum dimensions suggested by Woodcut saving all these problems.
Thank you again for your reply