Ultimate scraper

[Mark Rainey]

One of the StewMac scrapers has a straight edge and a slightly concave edge. If you use a grinder to get a burr on the scraper, how do you get a
burr on the concave edge?

[Jim Koepke]

A burnishing rod will work on straight, convex or concave scrapers:

492762

HSS drill rod was used to make this burnisher and scratch awl for my grandson > https://sawmillcreek.org/showthread.php?294562 < I have a couple others in the shop.

jtk

[Maurice Mcmurry]

These are hardened steel, square or concave edge, thick scrapers that do not require a burr. There are several good threads regarding these.

Stewart MacDonald Ultimate Scraper (https://sawmillcreek.org/showthread.php?282116-Stewart-MacDonald-Ultimate-Scraper)

[John K Jordan]

One of the StewMac scrapers has a straight edge and a slightly concave edge. If you use a grinder to get a burr on the scraper, how do you get a
burr on the concave edge?

I mostly use the two rounded scrapers. To sharpen the one you mention I held it flat against the tool rest and rotated it slightly so it missed the flat part of the wheel and ground with the edge of the wheel, very lightly. I use a 600 grit CBN wheel to sharpen these and many other tools.

FWIW, I ground a slight radius on the corners on either end of the long straight side to prevent scaring a wider flat wood surface. The effect is similar to bending and tilting a conventional cabinet scraper which lifts the corners slightly off the wood. There are still two sharp corners if I want to scrap into a tight corner of a carving or turning.

JKJ

[Mark Rainey]

A burnishing rod will work on straight, convex or concave scrapers:

492762

HSS drill rod was used to make this burnisher and scratch awl for my grandson > https://sawmillcreek.org/showthread.php?294562 < I have a couple others in the shop.

jtk

Thanks Jim, but I believe the Ultimate scraper is different. They recommend grinding a burr on it.

[Mark Rainey]

These are hardened steel, square or concave edge, thick scrapers that do not require a burr. There are several good threads regarding these.

Stewart MacDonald Ultimate Scraper (https://sawmillcreek.org/showthread.php?282116-Stewart-MacDonald-Ultimate-Scraper)

Maurice, I do believe they recommend grinding a burr.

[Mark Rainey]

I mostly use the two rounded scrapers. To sharpen the one you mention I held it flat against the tool rest and rotated it slightly so it missed the flat part of the wheel and ground with the edge of the wheel, very lightly. I use a 600 grit CBN wheel to sharpen these and many other tools.

FWIW, I ground a slight radius on the corners on either end of the long straight side to prevent scaring a wider flat wood surface. The effect is similar to bending and tilting a conventional cabinet scraper which lifts the corners slightly off the wood. There are still two sharp corners if I want to scrap into a tight corner of a carving or turning.

JKJ

Thanks John, I will try your approach.

[Maurice Mcmurry]

I do not think of a ground edge as a burr but in fact it is. On these scrapers it is not a task for a burnishing rod. Thanks Mark for the correction!

[Derek Cohen]

I made my own several years ago. This is how one is sharpened …

https://i.postimg.cc/HHXsk8Nh/Sharpening-blade-scrapera-zpslgrvfjha.jpg

Regards from Perth

Derek

[Mark Rainey]

I made my own several years ago. This is how one is sharpened …

https://i.postimg.cc/HHXsk8Nh/Sharpening-blade-scrapera-zpslgrvfjha.jpg

Regards from Perth

Derek

Thanks for your advice Derek, however the challenge is creating a burr on the concave side of the scraper using a square wheel. John Jordan shared his method. Have you used your grinder on the concave side of the scraper in a similar fashion to John's method?

[Maurice Mcmurry]

For the concave section of the scraper you need a thin wheel with a convex profile. Like an ice-skate sharpener, only used crosswise. You can only use a flat wheel if you are willing to compromise your wheel and grind on the corners. Or you can dress a thin wheel yourself into a convex form.

492772

[John K Jordan]

There is only one good reason I know to buy a CBN wheel with radiused “corners”, otherwise they have several distinct disadvantages.

Note the scraper Mark asked about has an extremely shallow concavity: a special thin convex wheel is not needed and probably not desired, in fact it might be hard to control by hand to achieve a smooth concave grind. Light grinding on the corner of a CBN wheel compromises nothing and is relatively easy to control. In fact I grind aggressively on the corners of CBN wheels to shape and sharpen certain custom tools. (All my CBN wheels also have 1” of flat grit on the sides which helps with custom tool creation.)

For those who don’t know a CBN wheel cannot be dressed. One could of course dress a fine AlOx or ceramic wheel to create a custom convex face. That wheel might have limited general use. One could also order a custom CBN wheel with an appropriate convex face.

If grinding many of these StewMac scrapers ot might be useful to invest in special tooling. Perhaps that’s what Stewart MacDonald did to prepare the large scraper for sale.

JKJ



For the concave section of the scraper you need a thin wheel with a convex profile. Like an ice-skate sharpener, only used crosswise. You can only use a flat wheel if you are willing to compromise your wheel and grind on the corners. Or you can dress a thin wheel yourself into a convex form.

492772

[Derek Cohen]

Thanks for your advice Derek, however the challenge is creating a burr on the concave side of the scraper using a square wheel. John Jordan shared his method. Have you used your grinder on the concave side of the scraper in a similar fashion to John's method?

Mark, I do not have a thick concave scraper. I do have standard, thin ones, however. If I had a thick version, and used it frequently (otherwise why have it), then I would use a rounded pink wheel, say 120 grit.

Regards from Perth

Derek

[Reed Gray]

I do not have the Stew/Mac scraper. I did see a video about it some time ago. The standard burnishing tools used for our card scrapers will have a very hard time, pun intended, burnishing a burr on that scraper. If you have some carbide rod, like a small router bit, that can burnish a burr on it. They don't say what type of metal it is. I would suspect that it would be similar to the M42 HSS that many turners are using now days. I have taken my gooseneck card scrapers and stood them on end to grind the top surface that you burnish to raise the burr, and that does work. Not sure if the concave part of that scraper would come close to matching the arc of an 8 inch wheel or not.

robo hippy

[Edward Weber]

Remember, the Stew-Mac scraper is NOT supposed to have a burr like a standard card/cabinet scraper.
The Stew-Mac scraper uses what is usually called a "keen edge", much the same as using a piece of glass.
https://www.stewmac.com/luthier-tools-and-supplies/types-of-tools/scrapers/stewmac-ultimate-scraper/

[Mark Rainey]

Remember, the Stew-Mac scraper is NOT supposed to have a burr like a standard card/cabinet scraper.
The Stew-Mac scraper uses what is usually called a "keen edge", much the same as using a piece of glass.
https://www.stewmac.com/luthier-tools-and-supplies/types-of-tools/scrapers/stewmac-ultimate-scraper/

Ed, I think you can use the Ultimate scraper without a burr for fine work, but the video by Caruthers definitely illustrated how he grinds a burr for best performance.
This type of scraper has turned up in the past. Gene Landon would grind a burr on a power hacksaw blade for scraping.