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ScaredyCat

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I've turned half a dozen bowls now and one of the things I've noticed is that the stream shavings coming off are warm. Ok, I'm working in an unheated space with bare hands and carbide tools. Is this normal or am I pushing too hard or something?



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KimG

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It depends really, how warm? I mean, hot shavings could indicate your tool is blunt, or the speed is too high, if the wood is very hard and dry it's inevitable that some heat will be generated, so check the tool is sharp, take modest cuts (light pressure) and possibly slow the speed (depending on how the first two go). You can sharpen carbide tips (the flat on top sort) by putting them flat side down on a diamond stone and grinding a new edge.
 

Dalboy

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I agree with Kim. Many times, especially with Oak(being very dry and hard) and a sharp tool I have turned the speed up and the wood comes off warm but that is my own fault.
 

ScaredyCat

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Thanks for the replies,

Temperature wise I'd say it was warm enough to notice as they hit my hands, not burning hot and it wasn't an unpleasant feeling. All the wood I've used so far came from EnglishWoods on ebay and they were all sealed with wax and dry.

Admittedly I was taking quite a bit off, but nothing that I haven't seen others do and I haven't really been applying much force since at that point I was relying on hot glue to hold the piece whilst I worked on the inside.

I'll try slowing the lathe a bit, I have been experimenting with cut quality and speed, so that might be it. I'm hoping that my carbide tools haven't become blunt over just 10 blanks though. I'll rotate the cutters and see if that changed anything too.

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CHJ

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Not unusual for the wood shavings to be too hot to be comfortable on your fingers or hand leaving the flute of a gouge.

Not a problem for the tool with Carbide or HSS tools, although you can heat thin HSS tool cutting edges to the point of bluing with the friction if not careful which can burn you quite badly.

Parting tools when used for deep partings are notorious for showing signs of heat discoloration, but this is due to friction because of lack of side or chip clearance and binding not the cutting .

If you ever use older carbon Steel tools then heating the cutting edge to these temperatures will destroy the tempering and render them soft and unable to hold an edge.
 

hodsdonr

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It is normal and more so when turning kiln dried wood. If you look at metal turnings then you often/usually find the the metal chips coming off are blue from the heat. And this is even when copious amounts of coolant are used.
If you go into the literature on metal turning , then you get info like 50% to 75% of the energy used in machining/turning ends up as heat. So getting a little warm is normal. And if you turn cherry some turners use a glove to prevent burning your hand as the shavings get so hot.
 

Fitzroy

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With metal machining the intent is the chips take the heat away, don’t see why it would be different for wood. I except blunt tools you’ll get scorching of the wood as you’re rubbing not cutting and the heat stays in the tool or with of body.

Fitz.
 

Paul Hannaby

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The heat is evidence of the friction generated by the tool and is partly due to the amount the shavings are "bent" when they are released by the cut. Scrapers and parting tools "turn" the shavings through a greater angle which generates more internal friction and heat within the wood.
The sharpness of the tool may also contribute to the generation of heat - blunt tools generate more heat than sharp ones.
A sharp gouge won't heat the shavings up much because the angle of a correctly presented gouge against the wood creates releases the shavings with less "bend", causing less friction and less heat.
 
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