sharping for the lathe

[sconi]

I was just wondering the sharpening angles for chisels for turning, when using the SS sharpening guide, if I recall I was told the tools that come with the SS should be sharpened at 8 degrees the bowl turing set at 4 degrees, what would be the suggested for the pen turing set, and particulary the 9 in one mini tool, and how the heck do you use that thing anyway. Thanks

[Rwsimons@web.tv.net]

l was told at the shopsmith academy and it was 10 degrees left for the gouge, 13 degrees left for the skew,8 degrees left for the parting tool with quick bursts, the round nose scraper is set at 0 degrees with the bevel side up. Your best bet would be to attend a shopsmith woodworking academy near you, the instructors are some of the nicest people you could meet.All the angles were left of 0 degrees.

[Nick]

Something you may want to consider, Sconi, is that the Shopsmith chisels come ground at a "utility" angle that can be used for both scraping and shearing, but isn't optimum for either.

(For those readers who are new to lathe turning, scraping and shearing are the two cutting techniques used to shape a turning on the lathe. When scraping, you position your tool near the middle of the turning and scrape away the wood; when shearing, you place it near the top and slice the fibers.)

Here's a chart of tool angles (the angle between the face and the back) for both shearing and scraping tools:

Shearing
Skew -- 30 degrees
Roughing Gouge -- 45 degrees
Spindle Gouge -- 30 to 40 degrees (higher angles for harder woods)
Bowl Gouge -- 40 degrees
Parting Tool -- 30 degrees

Scraping
Skew -- 45 to 50 degrees
Parting Tool -- 45 degrees
All Other Scraping Chisels -- 75 to 80 degrees

As for the 9-in-1 chisel in the pen turning set, nobody here seems to know. Our lathe expert (Dave Folkerth) is out for a week or so; I'll ask him when he gets back.

With all good wishes,

[Greenvilleguy]

Nick,

I ground a 3/8 SS bowl gouge into a fingernail grind and found it too agressive. I returned it to a normal grind, but wasn't sure I had the angle correct so I looked up your chart above.

I'm a little confused. I don't understand the the angle between the face and the back refered tp above. If I measure the bevel angle from the bottom of the tool 90 deg would be straight up, 120 deg would be fairly straight and 150 would be very angled. Based on this, should the bowl gouge be 130 degrees from the bottom, i.e. the 40 degrees above plus 90?

[Bruce]

Nick,

I ground a 3/8 SS bowl gouge into a fingernail grind and found it too agressive. I returned it to a normal grind, but wasn't sure I had the angle correct so I looked up your chart above.

I'm a little confused. I don't understand the the angle between the face and the back refered tp above. If I measure the bevel angle from the bottom of the tool 90 deg would be straight up, 120 deg would be fairly straight and 150 would be very angled. Based on this, should the bowl gouge be 130 degrees from the bottom, i.e. the 40 degrees above plus 90?

Nick is referring to the angle at the tip from the back of the tool, i.e. the angle between the bevel and a line extending out from the back/bottom of the chisel beyond the tip of the tool. You are measuring the complementary angle from the handle end rather than the tip end. By Nick's description, 30 degrees would be 150 degrees using your description. Clear as mud, right?

[Nick]

I don't understand the the angle between the face and the back...

On most lathe chisels, the "face" is surface you grind to create the tool angle, while the "back" is the surface that's left flat. These terms can be a little confusing because on the skew chisel you grind two surfaces to create this angle. There is no back to a skew; it has two faces. In my book Sharpening, I discarded the terms "face" and "back" and labeled one metal surface the "leading face" and the other the "trailing face." The tool angle is simply the angle from one metal surface to the other at the cutting edge. To forestall further confusion, here's the illustration from my book:

[ATTACH]30[/ATTACH]

P.S. Still hoping to solve the mystery of the 9-in-1 tool someday. Stay tuned.

With all good wishes,

[Greenvilleguy]

Thanks! Based on this, all of my gouges have 5 to 10 degrees too much bevel.

I wonder how that effects performance.

[deanthom]

As was mentioned in another thread, it's important to remember that most tools come ready to be modified for your use. That includes not only just plain sharpening, but even the establishment of angles.

Nick's explanation of the angles and the fact that SS tools come with "utility" angles is good. I'd like to add that folks have been "discussing" what proper angles for lathes tools should be for years. There is still precious little consensus.

Some of the most respected turners in the land have come to the conclusion that you should figure out what YOU're going to be using the tools for and make the angles that YOU find work well. One nationally known and respected turner now sharpens all of his gouges to 45º, whether they are fingernail, bowl, spindle, detail, or any other sort of gouge. He says that keeps him from having to make adjustments or decisions. No memory problems, either, for some fancier grind. They are all simply 45º. And he makes the bulk of his living selling his turnings. Most are NOT what you'd consider "art" pieces.

Truth be told, you have to determine what works for you within an acceptable range of angles. Too sharp a tool angle and the edge lasts one cut. Too blunt an angle and you'll never keep the bevel rubbing at the bottom corner of your cuts.

Same deal with scrapers and angles and burrs. The latest rage is "negative rake" scrapers. It looks like a skew designed to be used on its side, often with the burr left on.

And then the "to burr, or not to burr" question. Asking this in a group of woodturners is kinda like asking a golfer if he breathes in before or after he drives. Makes him think and confuses the heck out of him! And the arguements pro and con, big or little burr, yada yada yada. Funny to watch the blood pressure rise.

You've already recognized that if you get your angles too far out of the window of "acceptable", you're going to end up with tools that are not efficient or practical. Find out what works for you, document it, and stick with it. Don't change until you really have a good reason to do so. That will usually mean that you've tried someone else's exact same tool with a different angle that works better at doing what you are doing. THAT, IMO, is a good reason for changing. Otherwise, I find that I end up chasing the wind, spending more time worrying it out than turning. NOT a good thing.

Tip: Buy a HSS tool of similar size and shape that you can sacrifice as you learn. Those tools get short enough quick enough as it is. Drop me a note off list if you want me to go into more detail.

[Greenvilleguy]

This thread has really been helpful.

I went to a Woodcraft natural edge bowl class (Christmas present) last week and really liked the bowl gouges they provided. I asked the instructor there what the angles are and he has no idea. I did however discover his "formula" for fingernail grinds on bowl gouges.

He uses the Wolverine jig as do I. He has a stick that is 7 inches long with a 2" notch at the top. He sets the Wolverine jig up with V notch 7 inches away from where he wants the tool to hit the grinding wheel. The two inch notch is to allow him to set the gouge into the special fingernail jig 2 inches from the end of the tool. The fingernail jig is set in the 2nd notch.

I'm going to give this a try and if I can achieve the same results, I'll post the actual angles.