Another Question -- Skew Bevel Angle

[Dave C. Brown]

Folks,

I have another question, but it seemed best to have it separate from the tool rest one.

I recently watched Mike Darlow's sharpening video and he suggests a 25 degree angle for the bevel of a skew chisel (12.5 on each side). Rowley in his book also suggests this. I've seen other places (I seem to remember on the Thompson tool site) a recommendation of 40 degrees. I think Lacer's formula of having the bevel 1 1/2 times the thickness of the tool would also come out to about 40 degrees. Richard Raffan is not very specific in his book.

I believe most tools are shipped with about a 40 degree bevel on the skew.

So, at what bevel angle do you sharpen your skew chisels? Why? As someone who does not want to grind and regrind his skew too many times, I'm hoping you can shed some light here.

Thanks for any thoughts on this.

--Dave

[Gordon Seto]

Dave,

Another skew master, Alan Batty recommends 25° to 55° included bevel angle, depending on the hardness of wood. Sharper angle for softer wood and closer to 55° for durability of edge if you are working with dense hard wood. Sharper angle like 25° also allows for clearance for close together details. He suggests 40° as a compromise.

Gordon

[Dean Thomas]

Hey Dave,

Three turners, at least 4 opinions!!

Alan Batty's son Stuart was here in KC a couple of weeks ago. He talked a little about skews. His opinion was, "Why use 'em at all? Gouges sharpened right will allow you to do virtually everything that a skew will." Talk about a line that opens ya up for flying debris from all corners!

I'm going to toss in another variable. What about the angle of the cutting edge itself? Not the bevel (I'll get there in a minute), but the angle of the edge relative to the top/bottom of the tool. Some say 45º, some say 70º. Some, like Stu Batty, say, "Whatever works for a door stop!" I personally like the 40-60º range, leaning more toward 40-45º.

About the bevel, I liked Alan Lacer's explanation. I have no idea where he got it or if he worked it out himself, but it seems to work fairly well at avoiding getting the edge so fine that it dulls immediately. His recommendation is that the length of the bevel should be 1-1/2 times the thickness of the tool. That means that if you've got a skew made from 1/4" steel, your bevel will be 3/8" long. If your skew is 5/16 thick, the bevel would stretch to about 15/32" (just short of 1/2"), and if your skew is 3/8" thick (we shall not be moved! Everybody sing now...) the bevel would be about 9/16" long. In all cases, the angle comes up to a total of about 36º or 18º on each side. So for those of us who are NOT purists, that sounds a lot like anything between 35-40º would be workable for Mr. Lacer.

Others recommend any where from 25 to 45º. And those are only the ones that I found quickly! Shopsmith (don't hit me) has a jig for sharpening their tools to their recommended angles. The skew angle they recommend is between 30 and 45, but what they show is closer to the 35-36 that Lacer recommends. Difference is that since they grind theirs with a 12" sanding disk, the bevel is flat. They also recommend using 120 grit paper to shape, 220 and 320 grit (or even higher if you want a polished bevel) to finish it up and prep it for use. FWIW. Their jig is adjustable, but it also is fairly repeatable so a body could get consistent, repeatable angles. Like someone else mentioned on another thread, consistent, well-done grinding really makes a difference in our turning.

Last sawdust session at one of the local woodturners clubhouses, we talked a lot about skews and their sharpening. More than a few of them said that their skews had never touched a grinder, that they were hand-sharpened only. Part of that was to ensure that the bevel was not hollow-ground. The club grinder has 8" wheels. The longer the bevel on a skew, the more "air" you have between the line drawn from edge to heel of bevel. And when I come home, my grinder only has 6" wheels, meaning more air yet.

That air translates to an even steeper grind on the cutting edge. Steeper grind means that the edge is keener and more fragile, and that it does not last as long. At least in my experience. Another turner used his 8" wheels to establish the angle & point, but then honed the edge until there was a polished mark on the heel and the edge. Easier to hone air than steel, for sure. That's an old-timer plane and hand chisel trick for making super sharp hand tools. Works great, been using it for a lot of years, but have not used it on my lathe tools.

I have a couple of less expensive skews that still have their stock angles. One of them is pretty comical. 90º!!! Heck, my axe has a more acute angle! Another has a total angle of 60º again, it doesn't cut a whole lot. But then, tools come ready to be prepared, not ready for use, right???

[Ken Fitzgerald]

Here's my take on it and it's worth exactly what you pay for it.......

1. The skew has become my favorite tool. It's taken some practice on my part but it is indeed my favorite.

2. I'm a 25 degree man I think. The length of the bevel is measured to be 1 1/2 times the thickness of the skew. What I found in my experience is that if the bevel measures greater than that proportion, the tool in my hands became harder to accurately control. With an angle less than that, a small change at the handle resulted in too much of a change at the bevel end.

JMHO.......

[Bill Fleming]

The following is what I recently posted on the Tormek discussion group:

A few weeks ago I asked whether anyone had experience with sharpening turning
skews in
a manner like recommended by Alan Lacer. I was especially interested in
experience
sharpening the "Alan Lacer" heavy skew.

I got no input so proceeded to figure it out.

At first I assumed that I could do as recommended by the Tormek manual for skews
with
curved edges. The problem is that the Lacer skew (large size) is too large for
the SVS-50.
I modified mine to fit the larger skew chisel but while you can get it to fit
the skew is too
large to allow the jig to properly work.

So how to sharpen large skew with the Lacer edge?

Us the SVD-110 with the stone turning toward the edge. Set the bevel to match
the Lacer
bevel. Sharpen starting at the "long point" and sweep along to the "short
bevel." Do not
try to go from the "short point" back toward the "long point."

So that is the story.

Bill

[Paul Heely]

The Lacer method of 1-1/2 times the skew thickness will result in an included angle of 39º, actually its 38.94244.......

Sorry the engineer in me couldn't keep seeing the 1-1/2 times method mentioned with a variety of associated angles.

That said I have different angles on different skews. My 2 favorite are 39º and 25º.

[Jeff Farris]

This subject came up a few months ago between some of the fellows at Craft Supplies and me. The new TTS-100 Turning Tool Setter for the Tormek sets the bevel angle to 30 degrees. Craft Supplies en masse told me that the bevel was too long for most beginning and intermediate turners. Their classroom tools are ground with a much shorter bevel -- in the neighborhood of 45 degrees, some even shorter.

I started experimenting and found the following trade-offs. The shorter bevels are decidedly easier to control, with much less chance of gettting a catch. But, the quality of cut was less than I was used to. The longer bevel delivers a finished, polished surface, but catches are more likely and more disastrous. Alan Lacer once told me, the best cuts from a skew happen at the edge of disaster, which adds strength to Stuart's advice to forget the skew and learn how to use a side ground bowl gouge!

[Dean Thomas]

The Lacer method of 1-1/2 times the skew thickness will result in an included angle of 39º, actually its 38.94244.......

Sorry the engineer in me couldn't keep seeing the 1-1/2 times method mentioned with a variety of associated angles.

Thanks, Paul! Glad that an engineer came to the rescue and got the REAL number out there. Mine was strictly a derived figure from playing with a graphics package.

I'll write that down. 39º (or the Lacer method) has worked well for me. Nice thing is that it seems that it works that way for ANY thickness of steel. Is that presumption correct, Paul??


And Jeff, AMEN to good cuts just this side of disaster's edge! And Amen to the less than wonderful cuts achieved with a 45º angle edge. Ooooch.

And to add just a quick note to Bill Fleming's good notes on sharpening Lacer's curve, Lacer teaches that the 70 degrees of "skewness" is measured from point to point, not anywhere along the curve.

[Paul Heely]

Using the 1 1/2 times thickness method for the bevel will result in a 39º bevel angle regardless of the thickness of the skew.

[Dean Thomas]

Thanks for the info, Paul!! Good stuff.

[Dave C. Brown]

Paul,

Thanks for the confirmation on the Lacer Angle. I have a piece of paper with a triangle, some scribbles, some things crossed out, some formulas, some scribbles, a few more cross outs, and then I used the web to try and figure it out. I came out to your number, but hesitated and merely said I think it's about 40 degrees. Makes me think back to when I confidently asserted to my high school math teacher that I'd never use this stuff. I suppose I never thought it would be in woodworking either.

--Dave

[Mike Meredith]

Using the 1 1/2 times thickness method for the bevel will result in a 39º bevel angle regardless of the thickness of the skew.

This was the method Alan Batty gave out at his class last week. We had both Alan and Stuart at the same time. That was interesting. 40 degrees seems to be the panacea for all turning questions and the 1.5 timed thickness was the surest way to get to 40 degrees with a skew.

[Kyle Iwamoto]

Thanks Bill for that Tormek info. I have a too big skew too, and I'll have to try that sharpening technique. I asked that question long ago on the Tormek site and never got a good answer.

I free handed the skew and tried to guess what Lacer's bevels are. Now that I know it's 40, I'll have to stop guessing. I do like Lacer's angles. But then I'm still learning, so I guess I could adapt to any angle.

[Rusty Smith]

I've been using the skew exclusively for my pen turning lately. I've just used the angle that came on the skew and hand honed to sharpen. How is the angle measured? Say I'm looking for 40 degrees, is the angle measured relative to the long axis of the skew? If that is correct, then is it correct that one has 20 degrees on each side if the centerline of the tool?

[Ryan Baker]

I've been using the skew exclusively for my pen turning lately. I've just used the angle that came on the skew and hand honed to sharpen. How is the angle measured? Say I'm looking for 40 degrees, is the angle measured relative to the long axis of the skew? If that is correct, then is it correct that one has 20 degrees on each side if the centerline of the tool?

Yes, it's 20 degrees on either side of the long axis. And the skew angle is 70 degrees from the long axis (or 20 degrees from square).