burnishing

[Wes Ramsey]

I'm not too familiar with burnishing and haven't done it myself, but I get the gist of it. From what I understand given Reed Gray's writings, the rolled edge is necessary for clean, high-angle finish cuts. To be honest, as a noob turner I didn't waste many brain cells thinking about this cut, but the more I do it the better finish I get. Haven't had to use 80 grit in a while!

I haven't noticed much difference in my round-nose scrapers whether I sharpen the tool with the top up or down, but I don't do a separate burnishing step on the edge. I have noticed that the tool loses that edge rather quickly which has me thinking about burnishing rather than sharpening every few cuts and maybe make my tools last a bit longer. What is your process for burnishing, what tools do you use, how often, how much, and does it take the place of high-frequency sharpening?

[John K Jordan]

...the tool loses that edge rather quickly which has me thinking about burnishing rather than sharpening every few cuts and maybe make my tools last a bit longer. What is your process for burnishing, what tools do you use, how often, how much, and does it take the place of high-frequency sharpening?

I prefer the burnished edge over the grinding burr. For me the grinding burr is gone far too quickly.

I used to use this for big scrapers. It's great but easy to get too much force and roll the edge too much.

339341

These days I use a carbide rod in a handle, both for turning scrapers and for card/cabinet scrapers. It doesn't take much pressure. You should be able to feel the rolled edge. The round shaft of a HSS tool works as well as the carbide rod.

For a negative rake scraper, I make 2-3 passes holding the burnishing rod just a few degrees off the lower bevel. I do burnish again at least once before resharpening.

JKJ

[Wes Ramsey]

Thanks John! Was hoping for a few other replies, but apparently burnishing isn't common among turners. I will see if I can rig something up to burnish with the rounded edge of a file and see what shakes out. I think I have one that will work.

[Reed Gray]

I think I saw this one, then forgot.... I don't burnish as a rule, but need to go back and experiment some more. The burr for fine finish cuts is generally finer than the burr for heavy roughing cuts. The burrs you get from the different types of grinding wheels can be huge. I use the CBN wheels, and have for so long I can't remember what standard wheels do, but the burr from the CBN wheels is by far superior to the standard wheel so, excellent for heavy roughing, and off the 180 grit wheel it also makes nice high shear scrape cuts. The 600 and 1000 grit wheels make far better burrs for fine finish cuts, but not good for heavy roughing. The burnishing tool up above, isn't one I have used, but I agree that it is simple to over burnish with it to the point that you get a burr that rolls over too far, or is so big it is very catchy. I found some small carbide drill bits in the shop that I intend to make a small burnishing tool with. Not sure how much difference it makes using carbide compared to HSS for raising the burr.

John, do you have CBN wheels?

robo hippy

robo hippy

[John K Jordan]

...Not sure how much difference it makes using carbide compared to HSS for raising the burr.
John, do you have CBN wheels?

I saw no difference between the carbide and HSS. I use the carbide because many years ago someone on this forum, I think, was selling very nice carbide rods for not much money and I bought two of them and put one in a rosewood handle. That one is easy to grip and use. Either a HSS or hardened drill rod should work the same. Presumably burnishing a tool harder than the HSS rod or gouge shaft would eventually cause some wear but at the low forces we use I suspect any wear would not be noticed before thousands of uses.

I currently have four CBN wheels and another on the way:
10" wheel, 2" wide:
- 600 square edge for the Tormek

8" wheels on 1/2 speed grinders:
- 600 square edge
- 220 radiused edge
- 180 square edge
- 80 square edge on the way

All CBN wheels have 1" of grit down each flat face as well.
All are aluminum wheels from Ken Rizza, Woodturner's Wonders.
Your research and writings plus an endorsement from John Lucas got me replacing my Norton AlOx wheels with CBN.

I like the CBN wheels over the traditional wheels for sharpening lathe and woodworking tools but I keep the traditional wheels on other grinders in my little weld shop for carbon steel and rough grinding. (My favorite grinder there is a Metabo, excellent grinder.)

The 220 CBN wheel is up for trade if you have a use for it. I decided I have little use for a radiused edge but prefer the full width of the wheel and square corners on the edges. Also the 220 is to close in size to the 180. When I can afford it I want to try a 1200 on the Tormek.

JKJ

[Jamie Straw]

Doc Green has a very good, especially for "noobs", 3-part section on scrapers -- http://www.docgreenwoodturner.com/scrapers1.html for page 1. Writes about the different types of burrs, ways to make them, how to avoid mistakes, ways to grind. I like the Veritas burnisher -- it's screwed to the cabinet top in back of my grinder.

[Wes Ramsey]

Thanks for the comments guys! I'll check out that link, Jamie. May need to do some experimenting with file edge or drill rod. The burr I get from the OEM (80 grit?) wheel on my Rykon grinder is nothing special and doesn't last. Could also be that I've ground that one past where it is hardened good.

[John K Jordan]

...Could also be that I've ground that one past where it is hardened good.

You don't need a Rockwell hardness tester to get an idea of the relative hardness of various metals. The harder one will scratch the softer one. This method has been used long before accurate hardness testers were developed.

For example, carbide will scratch hardened steel, hardened steel will scratch softer steel, etc. You might get a good idea if you are into soft metal on a tool with the old file test - use a small file on several areas of a known good tool then compare the "bite" you get to the same filing on the tool in questions.

Without files calibrated for hardness you can't determine the precise hardness but you may be able to check the relative hardness.

JKJ