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Tiger
15th April 2009, 01:12 AM
I have seen it suggested that the final cuts should be shear cuts to achieve a nice smooth surface. I thought that a shear cut involves rubbing the bevel but have seen shear cuts defined as cuts made with the point of the tool on an angle without the bevel rubbing, so what is the correct definition of a shear cut and how does one perform it successfully? By the way, I'm not talking about shear scraping which I use on bowls and involves running a scraper at an angle of approx 45 degrees to the surface.

Ed Reiss
15th April 2009, 01:21 AM
There is a very good explination at this site

http://www.woodturningdesign.com/askdale/12/12.shtml

scroll down to the last Q&A

Skew ChiDAMN!!
15th April 2009, 02:23 AM
A shear cut is the same idea as shear scraping: the cutting edge is angled (usually around 35-45°) across the grain.

Bevel-rubbing is good practice for any cut, to give the cutting edge support and prevent catches, but basically irrelevant to the definition.

For example, when properly used a skew is always shear cutting.

(Well... that's my understanding of it, anyway. :p)

Tiger
15th April 2009, 10:39 AM
So, we can conclude that a shear cut is made with the edge of the tool, if the bevel happens to rub, it rubs, if it doesn't then it makes little difference. I would however say that when the bevel rubs you get that nice burnished surface. Guess it's a matter of deciding which type of cut to use as you finish your woodturning piece.

Skew ChiDAMN!!
15th April 2009, 03:05 PM
Yes; as far as the "definition" goes.

But when using shear cuts for finishing you don't want chatter marks or dig-ins, so it really is best to bevel rub whenever possible. DAMHIKT. :D

NeilS
15th April 2009, 04:15 PM
But when using shear cuts for finishing you don't want chatter marks or dig-ins, so it really is best to bevel rub whenever possible. DAMHIKT. :D

Ditto.

On woods that are more prone to tear out I will use as little as 10-15deg to the line of cut, using a swept back grind and cutting somewhere along the wing. Needs a delicate but firm hand to avoid corrugations on what is your final 'cut'.

Rubbing the bevel helps with control... think of the bevel rubbing against the cut wood as a small fulcrum around which the tool (and cutting edge) is rotated for precise control.... while sliding the tool along the tool rest, while raising or lowering the handle to maintain contact with the wood, while moving your body and feet to keep your arms in position and the curve sweet, while maintaining your posture and balance, while chewing gum, while whistling, while...:U

Clever lot us woodturners...:rolleyes:

Neil