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woodtryer
30th October 2016, 11:21 AM
I started turning a bowl from a "rough" piece of timber I had cut from a blackwood tree a few years ago. Started using my 16mm P&N bowl gouge which I had just sharpened on the vicmarc grinding with a 180g cbn wheel. It started cutting nicely but within 5 minutes or so the shaving coming off felt quite warn on my hands. All I can think of is that the gouge must be blunt already but it happened so soon.

I'm only new to woodturning so I am assuming that warm shavings are not correct and that my sharpening technique needs a review.

Any advice/feedback would be appreciated.

Regards,

Peter

Paul39
30th October 2016, 11:46 AM
I have had shavings come off both wet and dry timber hot enough to burn my hand. More so with dry hard timber. I don't think it is due to unsharpness. A dull gouge will not cut.

A square of cardboard slipped over the gouge to deflect shavings will save your hand if too hot. Put it behind the tool rest so you can see what the gouge is doing.

Welcome to the addiction.

Nubsnstubs
30th October 2016, 01:54 PM
Stuart Batty did a day long demo at our club in Tucson a couple months ago. Other than being an excellent woodturner, he knows how to sharpen tools. He stated that a sharp gouge has a life of about 90 seconds on. It's been my experience that that is a very true statement.

Did you check the end of your gouge to see if it was hot. Mine will get hot while I turn dry wood. I keep my gouge sharp and continue turning while doing the finger dance on the tool. ............Jerry (in Tucson)

woodtryer
30th October 2016, 02:26 PM
Hi Paul and Nubsnstubs, thanks for the fast reply. I didn't realise that hot shavings was common. So maybe my gouge isn't as "off" as I thought. I did take the gouge over to the grinder and gave it a freshen up and it cut nicely and still with warm to hot shavings which I shall no longer worry about.

Thanks,

Peter

hughie
30th October 2016, 03:47 PM
Hi Paul and Nubsnstubs, thanks for the fast reply. I didn't realise that hot shavings was common. So maybe my gouge isn't as "off" as I thought. I did take the gouge over to the grinder and gave it a freshen up and it cut nicely and still with warm to hot shavings which I shall no longer worry about.

Thanks,

Peter

I wear a glove on my left hand as some the hardwoods will produce chips.swarfe etc so hot it will over a few minutes damage the skin. The gouge will get hot due to the fact your 'rubbing the bevel' friction from this actions heats up the gouge tip.
As to the length of time a edge will last for me is dependant on the type or species being turned and the level of silica in the wood. I have known the edge to last much less than the 90seconds stated.

Simply put, ' the heat generation is caused by the cutting action of the tool'.

Richard Hodsdon
30th October 2016, 05:20 PM
Peter
Have a look at someone using a metal lathe. The swarf comes off and changes colour to a deep blue (ie heat treatmnet) even with plenty coolant. Also ask any machinist to show you the burn scars on their hands from the hot metal. The heating comes from the amount of energy being put into the piece in order to break the "bonds " holding shavings to the main piece (wood of metal) and when you consider the efficiency of the cutting action (dont know what it is but say 30%) then the excess goes into heat. I have seen the chips come off a lathe and they are glowing red.
The metal work bunch have gone into great detail calculating this conversion rate in order to improve the cutting tips and angles etc in order to reduce costs in their production turning.
Richard

woodtryer
30th October 2016, 05:39 PM
Thanks for all your feedback. I have a lot to learn about this woodturning business. I guess it was just a little bit worrying at first when I had hot shaving on my hand and my first thought was the gouge must be blunt. Now I know it's all normal I am happily shaking off hot shavings from my left hand :).

Thanks all.