On Edges & Tool Presentation

[Jeff Farris]

This show season, instead of just demonstrating the TORMEK out of our booth at The Woodworking Shows, we signed up to be the "Sharpening A to Z" eductional area. So now I give separate presentations on different groups of tools and how they are sharpened. I have a schedule (that I try pretty hard to keep to). My favorite session is my nearly one hour long presentation of sharpening turning tools. I try to pass along a lot of information about why tools are sharpened a certain way and also how to use the tools once they are properly sharpened.

That warm up is to explain a bit of an epiphany I had last weekend, when the previous week's SMC threads about TORMEK sharpened turning tools were rattling around in my brain.

I usually get the ball rolling by sharpening a very simple straight grind on a Robert Sorby 3/8" continental (forged) gouge. After sharpening and honing, I make a few cuts on the lathe, throwing beautiful curly ribbons off of dry cherry. Then I start talking about bevel angles and why different types of gouges are ground at different angles. I begin that section by explaining why the angle is important. If we're going to ride the bevel, we better have the bevel the right shape for the job at hand. That's the gist of my explanation, and I always make a few cuts on the piece of cherry to illustrate the difference between cutting and scraping. When the bevel is rubbing I shoot off beautiful curly ribbons. When the bevel is out of contact, I make a spray of sawdust and get a nasty torn out surface -- all from the same tool. Last Saturday in the middle of going back and forth between "spray of dust" and "curly ribbons" I noticed that my surface finish was not what I usually get and always expect. It wasn't awful, but it wasn't polished and shiny like it usually is. I didn't really think much about it until my presentation was over and I took a closer look.

Here's the point (finally, you say). The edge was "rolled". I have heard about "rolled" edges until I could scream. Until last week, I wasn't even really sure what that meant. Maybe I had not seen the phenomenon before because I don't scrape with my gouges. But at least now I know how an edge gets rolled --- it gets used improperly.

Unfortunately, the Charlotte show was kind of slow, and I had some time to experiment with different qualities of grind. The often repeated myth about highly honed edges rolling more than coarse or medium ground edges is just that, "myth". In comparing, if I would leave a moderately rough finish on the tool (as rough as you can get it with a TORMEK ), the edge would roll when used as a scraper just as quickly, or more so, than a highly polished edge -- it just wasn't as noticeable. The change in surface finsh after a few minutes of turning was more noticeable on a highly polished surface, because the surface was so good to begin with, but went to mediocrity in just a couple of minutes of being used as a scraper.

This did not change my mind on the value of honing tools. In fact, it reinforced my opinions. But, it did open my eyes to the fact that those who talk about "rolled" edges are very likely to be presenting the tool to the wood improperly -- unless they want to scrape. In which case, the polished edge is still the best way to go, but the bevel angle should be closed down to 60-80 degrees.

Sharp tools are one important element, but presenting them to the stock in the right way is just as important. Get those gouge and skew bevels rubbing!

FYI: This week the discussion of how NOT to use the gouge is going to be done before I sharpen it.

[Dennis Peacock]

Very educational Jeff. I admire what you are doing. I've demonstrated the Tormek several times, unlike you, I'm a rank amateur on demonstrating, but I have that passion for sharp tools and the Tormek was what got me loving sharp tools without all the time and hassle of hand sharpening with inconsistency.

Thanks for yet another educational piece on sharpening.

[John Hart]

As a tool abuser, I gotta say...What a great post Jeff! Thanks.

[Glenn Clabo]

One of those E-Pfff-E-knees Jeff? Informative post that explains alot about why people keep telling me...you don't have to have really sharp lathe tools.

[Bob Noles]

Great information Jeff and thanks so much for sharing it with us.

(Saving my pennies)

[doug webb]

Thanks for the information. Knowing no other turners here and there being no demonstrations such as you give, I get my "training' by reading and then experimenting. I do have a question though, obvious though the answer may be to everyone else. In respect to angles, where do you reference your angle to? Horizontal or vertical plane? 70 degrees and 20 degrees are the same distance from 90 degrees, but are not the same angle. So, your 60-80 degree bevel....... is it a sharp bevel or a blunt bevel. I believe I know but for once would like to be positive. Thanks again......doug

[Jeff Farris]

Thanks for the information. Knowing no other turners here and there being no demonstrations such as you give, I get my "training' by reading and then experimenting. I do have a question though, obvious though the answer may be to everyone else. In respect to angles, where do you reference your angle to? Horizontal or vertical plane? 70 degrees and 20 degrees are the same distance from 90 degrees, but are not the same angle. So, your 60-80 degree bevel....... is it a sharp bevel or a blunt bevel. I believe I know but for once would like to be positive. Thanks again......doug

A 60 - 80 degree bevel is a short bevel. a 25 - 35 degree bevel is a long bevel. Not to dwell on semantics, but "blunt" and "sharp" aren't very good ways to describe a bevel. I know you didn't mean it that way, but what happens is that things change in translation. You tell someone that a scraper should have a blunt bevel, then he tells someone else a scraper should have a blunt edge. After three or four transmissions, you don't even have to sharpen your scrapers at all!

The angle is measured horizontally from the flute. Spindle gouges should have bevels of around 30 to 35 degrees. Bowl gouges should be between 45 and 60 so that the bevel can rub even on the bottom of a deep bowl form. Roughing gouges should have bevels of 45 to 60 so that there's a bit more steel under the edge to hold up to the pounding of intermittent contact. Scrapers should be around 60 to 80 so that there is as much material as possible backing up the edge.

I know it is a long way, but if you come to Orlando for the show in a couple weeks we can get deep into this and up to our elbows in shavings -- no dust allowed.

[doug webb]

Thank you for clearing that up for me. Would love to attend show, but at this time I am unable to travel. Make a few shavings for me, please. Thanks again, doug

[Cecil Arnold]

Jeff, I'll take Doug's place when you get to Houston.

[Jeff Farris]

Jeff, I'll take Doug's place when you get to Houston.

Looking forward to it, Cecil.