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Bur on skew (Read 463 times)
 
Ed Weber
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Re: Bur on skew
Reply #15 - May 27th, 2019 at 12:47pm
 
This is an article on sharpening, though it's directed a sharpening knives, the principles are the same.
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And yes John, you are correct, a burr is crated by the sharpening process. You you can either utilize it as with a scraper. or you could also attempt to eliminate it by honing after sharpening.
A skew is nothing more than a peeling blade and the edge must be sharp with no burr present. The curvature of the edge (if any) along with the stlye and the geometry of the grind usually varies from turner to turner.
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Don Stephan
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Re: Bur on skew
Reply #16 - May 27th, 2019 at 3:47pm
 
Interesting that the last paragraph of the guide says the lower the sharpening angle on the stone, the sharper the knife.  One could argue that a cutting edge with no thickness at an included angle of 25 degrees is technically just as sharp as one with no thickness at an included angle of 50 degrees.  Whether peeling apples or turning a bowl, it might be easier to "pick up a shaving" with a narrower included angle, but technically sharp is sharp.
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Ed Weber
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Re: Bur on skew
Reply #17 - May 28th, 2019 at 10:41am
 
The width of edge (the intersection where the two planes meet) may be the same thickness, X microns wide. This is a measurement, sharpness is determined by how well an edge combined with the blade geometry cuts a particular material.

I may sharpen my butt chisel to 30 degrees on 1000 grit abrasive and sharpen my paring chisel at 20 degrees on a 1000 grit abrasive. Both are the same sharpness but one will cut differently (better or worse) than the other. because of the angle (geometry) of the grind.
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Don Stephan
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Re: Bur on skew
Reply #18 - May 28th, 2019 at 12:33pm
 
Agreed, that was the reason for the comment about "picking up a shaving."

Which do you shave with?  LOL
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Ed Weber
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Re: Bur on skew
Reply #19 - May 28th, 2019 at 3:42pm
 
Don Stephan wrote on May 28th, 2019 at 12:33pm:
Which do you shave with?  LOL



Well I'll tell you one thing, I don't test my blades by shaving the hairs off my arm.  Undecided
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Re: Bur on skew
Reply #20 - May 29th, 2019 at 8:47pm
 
If you skew your chisels when you cut, you get a more acute angle than you  do if the chisel cut direction is square to the edge. Some hand planes are skewed like that on  purpose.

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Rick Caron
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Re: Bur on skew
Reply #21 - Jun 9th, 2019 at 4:09pm
 
I've been talking about a skew.    I should have been talking about a burr on a NRS.    They need a burr.
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« Last Edit: Jun 9th, 2019 at 4:10pm by Rick Caron »  
 
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Ed Weber
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Re: Bur on skew
Reply #22 - Jun 10th, 2019 at 8:19am
 
Rick Caron wrote on Jun 9th, 2019 at 4:09pm:
I should have been talking about a burr on a NRS.    They need a burr.


This may depend on who you ask.
A scraper (positive rake with burr) is an aggressive cut
A NRS with a burr is a slightly less aggressive cut (can vary greatly)
An NRS without a burr is the least aggressive (can vary greatly)

Some people don't want a burr on a NRS. Much of this depends on the angle of the tools cutting edge, which can have a wide range from an included angle of 90 to less than 45 degrees. If you lay a skew (flat not oval) on it's side, you have a NRS.
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Re: Bur on skew
Reply #23 - Jun 10th, 2019 at 10:20am
 
Well, for sure, the Big Ugly tool with a burr can be very aggressive when removing stock, especially from bowls. The burr on a NRS is never very big, and I did see Jimmy Allen (owner of D Way Tools) use one with a burnished burr for roughing out his boxes, but to me, it is painfully slow. The grinder burrs are worthless for anything other than very light cuts since they have no strength to them, and are gone in seconds. I don't think I have ever seen some one use a NRS without a burr, but there are some carbide NRSs out now, and I have no experience with them. I have seen a standard scraper with the burr honed off, and it was used for finish cuts on some hard maple and left a very smooth surface. The original NRS was a skew chisel, and I had a work shop with Allen Batty who told us about making billiard balls out of elephant Ivory, and he used a skew. The skew chisel type of NRSs does not take a burnished burr well as you can hear the edge fracturing as you attempt to burnish. Most of the burnished burr types are in the 60 or 70 degree range for the bottom bevel, and 20 to 30 for the top bevel. The burnished burr is sharper and more durable than the grinder burrs, even if you sharpen with the bottom bevel up side down.

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Re: Bur on skew
Reply #24 - Jun 10th, 2019 at 1:22pm
 
robo_hippy wrote on Jun 10th, 2019 at 10:20am:
The burr on a NRS is never very big


robo_hippy wrote on Jun 10th, 2019 at 10:20am:
they have no strength to them, and are gone in seconds.


This was my point.
Also some curved NRS's (with equal bevel) can be used right side up or upside down. A burr would not be helpful unless you were to sharpen each time you used it in a different direction (left or right)
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Re: Bur on skew
Reply #25 - Jun 11th, 2019 at 9:47am
 
I was watching a video on NRSs the other day, and the turner had a right handed one, and a left handed one with 45/45 bevels on both of them.... You didn't know you could just flip it over and grind the burr on the other side???????

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Ralph Fahringer
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Re: Bur on skew
Reply #26 - Jun 11th, 2019 at 10:02am
 
I grind mine on the front side first and then the backside, giving me a burr on the front side.

When I use it, I use the front side first and then go back over with the back side to give me an even smoother cut.

If I know that I'm going to need it to get in closer to the chuck, I'll resharpen it so the burr is on the other side.


It takes more time for the grinder to come up to speed than it does to sharpen the tool....well.. it feels like it! Roll Eyes


I love my NRS! Smiley


Long ago, i got a box of old (REALLY cheap) lathe tools from someone who was going to throw them out and last year dug  them out and made a small NRS out of one and it works great in those tight places inside bowls and such.
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« Last Edit: Jun 11th, 2019 at 10:05am by Ralph Fahringer »  

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