Creating spiral cuts when turning the inside of bowls and platters

[LadyD]

Hi,
I’m a relatively new Turner and can’t seem to overcome or identify the cause of my problem.  I keep creating spiralling grooves when turning the inside of bowls/ platters.  The spirals have been in the area when coming from the sides to the base and also in bases.  These are very difficult to overcome once they’re in and it’s really holding me back.
I have been observed by experienced turners, whom can’t visually identify possible reasons why.  Please if anyone can offer any ideas, I would be very grateful.

[Paul Hannaby]

Welcome to the dark side!

I think what you are describing is a pattern of spiral chatter marks rather than a spiral caused by a catch? These are due to too much pressure of the tool against the wood so try resharpening the gouge to eliminate that as a cause and repeat the cut. Just apply downwards force with your left hand (assuming you are right handed?) to keep the tool on the rest. Sometimes it also helps to lower the toolrest a little so when it is cutting near the centre of the bowl/platter the gouge handle is lower than the cutting end.

If you haven't already done so, look up your nearest club on the AWGB website. I'm sure they would be happy to help.

[LadyD]

Thanks Paul, I really appreciate your reply.  I can confirm my tool was definitely sharpe, so can I confirm that you are suggesting I’m pushing the gouge towards the wood rather than down on the tool rest? 

[GBF]

I sugest you get some tuition from a profesional turner who would soon sort out your problems.

Regards George

[bodrighywood]

Also the amount of overhang can affect the chatter. As George says, best bet is get some tuition if possible.

Pete

[Bryan Milham]

Hi LadyD and a welcome from me as well.

Can you confirm that Paul was correct when he said it's a spiral pattern problem you are having, not a tool slip spiral.

Paul's give to great things to try, but you might also try changing the speed of the lathe rotation, if it's a variable speed lathe and also change the cutting angle of the tools bevel, that is hold it so not quite so much of the tool is making contact with the wood behind the bevels cutting edge.

Bryan

[LadyD]

Thanks Everyone.  I appreciate all your suggestions. I’ll hopefully find the answer from trial and error of all your suggestions.

[Paul Hannaby]

Yes, one possible cause of the spirals is too much pressure of the tool against the wood. Is the tip of your gouge getting hot during use? That's a good indicator if it is.

[willstewart]

As another suggestion this happens when the piece vibrates under the tool. Better technique and sharper tools can minimise this as already suggested but you should ideally do cuts that leave the part being cut as firmly held as possible.  For example do not hollow out the whole bowl and gradually make it thinner but hollow out in layers across the bowl diameter (as though it were level and filled with fluid).  This supports the bit you are cutting whilst leaving the thinner part near the edge that is more prone to vibrate untouched.  Works for me anyway!

[happy amateur]

It is also possible that it is caused by the heel of the tool dragging on the transition of side to bottom. A shorter bevel or taking away the heel to create a shorter bevel might work

Fred Taylor
orchard-woodturners.org.uk