Bevel Angles- Raffan (Henry Taylor) Radius Skew Chisels

[gjamison]

The TTS-100 offers only two presets for these chisels; with included bevel angles of either 30 or 45 degrees.
Most authors suggest angles of 25 - 30 degrees for soft woods; higher values for harder woods and less proficient users.
When I received the 1/2" and 1" chisels from Craft Supplies, the included bevel angle is roughly 60 degrees for the 1/2", and 45 degrees for the 1".
Raffan's book and video (which are excellent) does not include recommendations or a hint of what he uses (perhaps I missed it).
It seems odd that there are such high angles on these new tools given reported/published recommendations, and a general expectation that the bevel should be consistent with the developer's (Raffan's) practice/recommendations (otherwise why does it bear his name).  Further, there is an implication in the Tormek materials that the presets for the radius skews are largely influenced by Raffan's input/practice...the 30 or 45 degree choices.
So, before I start the slow process of seriously regrinding these tools, is there something I am missing...seems unlikely that Raffan would be using these at the angles they are produced at?  I am fully aware of the skill level issues, wood type, personal preference, etc,...I am a novice turner, prefer cherry and similar woods.
My instinct says reshape the 1/2" to 45 degrees, and clean up the 1" at its present 45 degrees and try them.  I am hesitant to grind new chisels down to the 30 configuration only to find it was a big mistake.  I also realize I am not bound by the presets.

Thank you

[Ken S]

Welcometo the forum, George.

We had a topic several years ago concerning how Richard used his Tormek (horizontal or vertical) when sharpening gouges. I was curious to read what the master himself might say, so I got up on his website and sent him an email. He sent a nice reply. He also gave me permission to post his answer, which I did. I suggest you contact him. Please post his answers. He seems like a nice, helpful guy.

As a novice turner, I would suggest you start with the basic settings. They are a product of much research by a Tormek committee which included Jeff Farris. If you do not already have the Tormek woodturner's information kit (DVD and book), it is a must. I consider it Tormek's best DVD.

I did a lot of study in determining bevel angles while developing the kenjig. It is for knives, but started out as a way to automate chisel bevel settings. The theory would apply to skew chisels, too. I suggest you locate the document I posted on the forum explaining the kenjig. I think you would benefit from printing and studying it. A simple kenjig or several for different bevel angles could be easily made at home.

I am away from my home computer. I will write more in a couple days

Ken

[Rob]

Let me "yes and" Mr Raffan's comments. If you watch his much praised video "turning projects" and closely scrutinise his skew, you'll notice the bevel is really short. This means the included angle it's ground at is high. Certainly way more than 30 degrees and I suspect there are a number of reasons for this:

1) he lives in Canberra and turns a lot of Australian hardwoods like Jarra et al which will blunt a low angle quickly
2) his skew technique is arguably the best ever seen in the global Woodturning community. He's fast, merciless with the risks he takes and yet rarely gets a catch and a "blunt" angle serves that technique
3) if you notice his grip it's the primary secret to his success with that grind. He hooks his forefinger under the toolrest which gives massive control over the tool because of the downward pressure into the work. He takes big bites and much like the principle of the meat cleaver "blunt" bevel to go through bone

The combination of these factors have evolved his unique approach which is why I think he's recommending the standard approach/angles while you get some hours in front of the lathe. I can't answer the question about why his signature tools don't map his style other than to suggest the majority would benefit by "not" copying his grind for the reasons stated above. At the end of the day when a manufacturer offers to pay you a royalty for every tool they sell in your name, to a struggling artist Woodturner, regardless the grind, that's a good deal!

So it's possible other commercial forces are at work behind the grind that comes out the factory with his name on

The basic problem is he's in a league of his own he has such skill

[Ken S]

Rob,

Outstanding post! Not being an active turner, I missed what you observed. I am glad you posted!

Now, back to matching bevel angles. With a skew we have two variables plus the skew angle. Set the skew angle first. Then set the TTS-100 to the grinding wheel using the setting (A or B), whichever is closer to the bevel angle you want. Blacken the bevel with a marker. Place the skew in the jig and eyeball the projection distance to where the bevel appears flat on the grinding wheel. Turn the grinding wheel by hand until you are happy  that the projection matches your bevel.

I placed a piece of white label tape in one of the projection slots of my TTS-100. Place the skew in the jig into the slot and make a mark where the long point is on the label tape. Label this mark. (X degree bevel with X skew setting A or B).

For future sharpenings, set the skew angle; set the  universal support with the TTS-100 with setting A or B; and set the tool projection to the point marked on the label. Fast, easy, and accurately repeatable.

There are variations on this technique. I think this is the easiest way.

Good luck and keep posting!

Ken

[Jan]

George,

In the picture below you can see how I use the square edge jig to sharpen straight edge of standard skew chisels.



The chisel shown has an edge angle 60^o and skew angle 30^o. In this configuration you are not limited to settings predefined by the TTS-100. May be it will inspire you to shape curved edges using the multi jig.

Good luck!
Jan

P.S.: The usage of the angle master is only indicative because the values are biased thanks to the skew.  Use the notches of the angle master to check the real edge angle.

[Ken S]

Jan,

Your well done photo illustrates the need for good light when using the anglemaster.

As much as I value precision, "only indicative" seems "within tolerance" in this case. 

Ken

[Jan]

Ken, I have added the caveat because there are two ways how to measure the edge angle of a skew chisel. Either perpendicular to the edge or parallel to the side of the blade. 

Jan

[Ken S]

Good thought, Jan.

In this case, I believe either would be accurate enough. My thought is to be able to set a bevel consistently and repeatably. I don't believe a degree or two in either direction is critical.

Ken

[gjamison]

Thank you Ken, Rob and Jan for your response.  I haven't figured out if there is a way to post a reply to individual responses, so this aggregated reply.
Ken, I am familiar with Ruffan's use of the vertical rest...thanks.  I had not considered contacting him re the bevels on "his" Henry Taylor tools, but may.  The suggestion to use the basic settings (presets) matches my preference; I have found the book and dvd very useful.  However, as stated in my post, the question is, which of the two presets for a radius skew to select (if not some other value).  Of the two presets, Tormek would say use 45 degrees unless you are a pro.  Thanks for the kenjig lead.  Your response to Rob is basically the technique I use for non standard settings, including the use of spacer blocks (in lieu of hole A or B).
Rob, I take your "yes" in the reply to be agreement that Raffan would likely not be using radius skews at the angles they are being produced?  I too had noticed that his bevel lengths appeared "short" in the videos...not what a 25 or 30 degree included angle looks like on bevel length.  Great observations on reasoning for his higher angles.  You mention believing that Raffan is recommending "standard approach/angles" until experience is gained.  The Tormek choice thus would be 45 degrees.  I that what you are suggesting/referencing?  That's about where the 1" is factory ground...the 1/2" at about 60 degrees is another story...like your meat cleaver description.
Jan, thanks for the helpful image; interesting approach to use the square edge jig...for straight edge skews.  Had to grin at the caveat re the angle measurement...normal to the edge or along the side of the tool.  As an engineer, I suffer from similar thoughts...in fact I posted another topic basically asking why Tormek doesn't give us the equations or at the least the dimensions they use, so we could work up or own set of presets.
Overall, I feel more inclined after these replies to grind the 1/2" down to 45, and leave the 1" at 45...just clean it up.  Seem reasonable?   Don't want to suffer from paralysis by analysis...been there more than once.
Thank you all.
George

[Ken S]

George,

Good post! It gave me a good laugh. "Paralysis by analysis" Great phrase! 

I would suggest just starting with a standard repeatable setting and marvhing on; you'll do fine!

Ken

[gjamison]

Ken,
Engineers are accused of the paralysis by analysis malady, most often mistakenly by spouses, family and friends.

George

[Jan]

George,

paralysis by analysis is the perfect phrase for my for my caveat concerning the edge angle definition for skew chisel. Thanks for your feedback, appreciated. 

My seeking for perfect solutions is given by my experience that in math even small discrepancy may indicate an error because "the devil is in the detail".

Just out of curiosity, the difference between the two ways of measuring the edge angle of the shown skew chisel is 7^o. The chisel bevel wobbles in the 60^o notch, when not inserted perpendicularly. 

Jan

[Ken S]

Jan,

It's a good thing that I am the moderator instead of the navigator. I had not realized the difference is seven degrees. Would either method work as long as we compensated for the difference?

Good find!

Ken

[RichColvin]

I'm certainly no woodturning expert, but I've found a good grind for my skew with which I can make a lot of really nice cuts.  I use a Sorby skew with an end that has a 70 degree angle (as shown below) :



I use the SVS-50, set at 20 degrees, a projection of 65mm, and hole B.

[Jan]

Rich, I am wondering what is the edge angle of your skew chisel? Based on your jig settings the edge angle should be 30^o. Could you please measure it using the notches of the anglemaster?

Jan