Bevel rubbing vs scraping

Re: Bevel rubbing vs scraping

Robert Edington

I suggest you look on youtube at Mark Sillay. I just took a class with him on wood slicing. We only worked on 2x4's. No sanding required. Finishes on the 2x4 smoother than anything you could get using sand paper. We used a 3/8" spindle gouge ground to a 30 degree bevel with the back of the gouge hollow ground. (He shows how to grind and all his techniques on the video. It's about an 90 minutes long. It can be found on the Guinnette Woodturners channel. The class I had with him was very eyeopening and rewarding. He's an outstanding instructor, who loves seeing success in his students.

RP

Re: Bevel rubbing vs scraping

john lucas

Mark is a friend and a really good turner and teacher. I have turned a lot of 2x4's and some of them will turn to a glossy finish with the right tools. One time I was doing demos at a tractor show. A guy from up North was standing at my booth and bad mouthing southern machinists so he had already ticked me off. Then he said yea some guys claim they can turn wood and not need to sand, that's a bunch of crap. I was turning a piece of 2x4 with a lot of sap in it using my skew. So I took my time and really worked it over. It came out with an almost mirror finish. I handed it to him and said, oh you mean like this. If you slow down your feed rate on woods like that the bevel will actually burnish the surface. Of course the tool has to be sharp enough to not leave any tearout what so ever. I've Done glossy finishes on Cocobolo using the Hunter tools.

I remember Mark saying he uses 30 degrees on his spindle gouge. Mine is 35. The Hunter carbide cutters have an edge that is somewhere between 25 and 30. I don't have a tool that will measure it accurately because it slopes but the first 2 mm is really acute and sharp.

Re: Bevel rubbing vs scraping

robo hippy

If I was there, I would let you use a shear scraper that was sharpened on a 600 and 1000 grit CBN wheel. I had a highly figured piece of sugar maple, and played around with it a bunch, with all sorts of different tools. Best 'zero' tear out was with the burrs from the 600 and 1000 grit wheels and a shear scrape. My skew skills are not very good. With it sharpened on the 1000 grit wheel, I could get a pretty good surface going one direction, then needed to hone the burr over to the other side to reverse directions. I need to work on my honing skills as well.... I need to play with the burnished burr for shear scraping too....

robo hippy

Re: Bevel rubbing vs scraping

John C Lucas

I have a 1000 grit sanding belt and can try raising a burr on that. However i have a John Jordan shear scraper and you raise the birr on that with a ceramic hone. Dont know the grit on that but its finer than 600 just using my fingers to feel. It leaves a very clean surface but not as good as i get off of a freshly sharpened gouge with at least a 40 degree grid or sharper. It will clean up chip out better on the uphill grain of a bowl that than i can with a gouge.

Re: Bevel rubbing vs scraping

John C Lucas

I need to try that ceramic hone on my Thompson negative rake scraper to see if it raises a better burr. That would be a wonderful tool to use as a shear scraper on the inside of a bowl if it raises a good burr.

Re: Bevel rubbing vs scraping

John K Jordan

Do you think there is a difference between the burr raised by the ceramic stone and one made with a carbide rod? I use the carbide but never tried a piece of ceramic.

I have the JJ shear scraper too but I also can't get as clean a surface as with the side of a gouge.

JKJ

Re: Bevel rubbing vs scraping

John C Lucas

I dont know John. I use it to the way i use a steel to raise a burr on a cabinet scraper. It has a rounded edge.that i lever against the point after using the flat side to polish off the old burr.

I ha e.been thinking about building something similar to the Veritas cone shaped burr raisig tool. I was just going to make the cone out of high carbon steel and leave it fully hardened. Do you think that would work?

Re: Bevel rubbing vs scraping

robo hippy

There are huge differences in burrs. The burr from a new 80 grit CBN wheel is bigger and coarser than one from an old broken in wheel. The one from a 600 grit wheel is much different than a hand honed one. These change according to how you sharpen as in just kissing the wheel, or pushing it in with some force. I do look at the hand honed burrs as being similar to burnishing since you aren't doing nearly as much cutting as you do with a wheel. I haven't tried the ceramic hones though. Hmm, I do have a ceramic knife sharpening thing in the kitchen that is too fine to be of much use.... The diamond and CBN ones seem to raise similar burrs, which are not as sturdy as the ones from the grinding wheel. For my carbide burnishing tool, I put an 1/8 inch 'resharpened' carbide drill bit into a steel rod with just the haft/butt sticking up. A couple of light passes is all it takes. For some reason, it doesn't seem to make any difference in how much I try, I can't hone off all of the grinder burr. I would consider a broken in 600 grit and/or 1000 grit wheel to be almost like burnishing as it polishes more than it cuts. Then there are the burrs where you hone across the face of the bevel, and the ones where you hone up and down along the bevel..... Well, that is a couple of days in the shop....

robo hippy

Re: Bevel rubbing vs scraping

John K Jordan

>>>I ha e.been thinking about building something similar to the Veritas cone shaped burr raisig tool. I was just going to make the cone out of high carbon steel and leave it fully hardened. Do you think that would work?

Do you mean the one that you fasten to the workbench that has both a cone for burnishing and a cylindrical pin for a fulcrum? I have one of those and I used to use it with my big scrapers. I haven't used it in years since I don't use the big scrapers much now. It will let you put a LOT of force against the edge. I don't think I'd use it for negative rake scrapers since the cone angle is too steep and no force is needed.

You can borrow it if you want to experiment.

The hardened steel rod should be sufficient. I've used all kinds of rods for burnishing but the reason I use the carbide now is because I have one. (Some years ago someone on this forum was selling the rods for cheap.)

JKJ

Re: Bevel rubbing vs scraping

robo hippy

Well, the burr I get from a carbide rod is different than the burr I get from a standard burnishing tool. I think the carbide advantage is that it is considerably harder than the steel rod, and to me, that seems to make it easier to turn the burr. The thing about the Veritas burnishing tool that with the pivot point rod, it makes it very easy to 'over burnish'. It actually takes very little effort to turn a burr, even on a 70 degree bevel scraper. It would not do a good job on a NRS, unless it was a 70/25 type NRS rather than the 30/30 types.

robo hippy