Problem pulling a bur on scrapers

[Randal Cobb]

Hello all,

I'm pretty new to the "non-powered" aspect of woodworking... just really learning how to properly use and sharpen things like chisels, scrapers, plane irons, etc. I'm having a small problem with a flat scraper... I can't seem to pull a bur on both sides of the same edge. I don't know if it matters and I can't remember the name of the manufacturer 'cuz I threw out the package, but they were bought from Woodcraft and came in a plastic "slide package" with a green card on the back, and remember reading they were made in England.

Anyway, I've found the couple of videos on the net on how to properly file off the old bur and use the burnisher flat along the edge to pull burs on both edges, and how to angle the burnisher to give the proper angle on the bur... but no matter what I've tried, I can only get a bur on one edge. I thought maybe I wasn't using enough pressure but that proved dangerous, it slipped off one edge and I have a nice gash on my left index finger to prove it (of course, I managed to do it against the only bur currently on the scraper).

Any suggestions on what I have done wrong (aside from slicing my finger half off)?

Thanks in advance!

[Bob Barkto]

About the only thing that I can think of is the edge is a bit off square.

As a test, make one straight pass with the burnisher on a freshly prepared edge and see if you feel an equal burr on both sides. It will be small but you should be able to feel it. Use your good finger!

Bob
...who has a 30 year old scar from a scraper burnishing mishap

[Don Naples]

Randy, the most important part of sharpening a card scraper is to make sure the edge is perfectly flat and square to the side edge. Sharpen the edge to 40 micron or finer. I do mine to 5 micron. (P2500 is 8.4 micron). When you roll the edge, make the first pass flat on the side to push out the steel at the cutting edge just a bit. Take a second pass at 90 degrees to roll the burr up and then take one pass at 5 to 15 degrees to roll a hook. You can see a video of this and taking shavings on Bubinga at http://www.youtube.com/watch?v=VzAYZ92z5C4

[Randal Cobb]

Thanks for the replies...

Don, yes, that is one of the videos I had stumbled across... good video. However, I don't have a sharpening system like that... I use waterstones for my chisels and have relied on the factory grind so far (I don't have a grinder yet, either).

For the scrapers, I'm using a jointed block of mahogany that I have rabbeted so it fits over the file which lays flat on the workbench. I run the scraper across the file to knock off the old burr, then use the bench vise to hold the card upright to use the burnisher.

So, either my jointed block isn't a true 90* or I'm not holding the burnisher at a true 90* when pulling the burrs. I'll re-check the block to make sure it's true 90* and then try the method shown in the video Don provided by burnishing with the card flat on the edge of the bench.

Thanks again for the suggestions, they both are probably exactly what I am doing wrong.

[Don Naples]

Randy:

The method of sharpening, by hand or machine, is not important. Whatever method you use, keep the edge flat to the side edge. If you site down the edge and see a secondary line of light reflection, then the edge is not flat. You are correct that to get a good burr on both edges you need the edge to be at 90 degrees to the sides. The finer abrasive you use (within reason) the longer the edge lasts (at least in my experience) and the finer the shavings you can get.

[John Thompson]

Good luck in the quest to get an edge on both sides, Randy. I started using them around 1975 and use them almost daily at this point. But... for whatever reason unknown to me, I could never get a duplicate edge on both sides.

I will get an excellent edge on one side and the other side has an edge but just so-so? I quit trying to get an edge on both sides years ago and for me, that was a wise decision. The reason is it takes me about 2-3 minutes to pull up the file.. remove the dulled and burnish a new which I do about 3-4 times a project usually.

The wise decision for me is that I am getting one excellent edge and that is all I can use at one time. And when it dulls.. I can put another excellent edge on again in a matter of minutes in lieu of spending countless hours trying to figure out why I can't get on edge on both.

Life is simple around the Sarge Shop.

Sarge..

[glenn bradley]

John Thompson has got it. I too will catch myself spending way too much time trying to get something "right" while I could be working. Don't get me wrong, I will spend a couple hours to make a jig if it will save me 5 minutes the next 100 times I have to do the same thing.

Like John I just go with what works. I clamp the scraper in a wood vise, hold a squared block of wood and the file in one hand using the block as a guide, do the same with a diamond stone and then burnish it. A few strokes of the file and just a couple with the stone. One or (maybe) two swipes (each, flat and at an angle) with whatever you are using to burnish and then stop. If I play with it, I just botch it and have to do it again.

[Mark Singer]

I think you have good advice. I get 4 edges on a scraper and intentionally make 2 of them more aggressive and 2 less. That way it is kind of like a 4 in 1 rasp and you have options. Use a honing oil when you form the burr. One common problem is that often when people start using scrapers they over form the burr and roll it into itself. You should be able to feel it with your thumb. As you scrape slightly vary the angle and you will find a sweet spot.

[Ron Bailey]

I've had trouble getting a satisfactory burr for years. I was using a Sandvik scraper
with a Hirsh oval burnisher. I had nothing to compare to so I figured that my
sharpening technique was to blame - got "The Complete Guide to Sharpening" by
Leonard Lee. It is an excellent book but I still had only modest success.
Finally I picked up a Hock round burnisher and wow, what a difference. I put a great
burr on the scraper and was I raising piles of ultra thin shavings instead of the dust
I was used to.
I don't quite know what the big difference is in burnishers. The Hirsh, made in
Germany, has a rather uneven surface but it is certainly hard enough, the Hock
is mirror smooth and very very hard.

[Wiley Horne]

Randall,

Try this right after you have jointed and detailed your edge, and are ready to put a hook on it. Mount one edge vertically in a vise. Take the burnisher--by the way, keep a light coating of oil or white grease on the burnisher, it'll keep it from galling the edge. Anyway, with the edge you're going to work standing up vertically, take the burnisher and hold it horizontally--dead level with the edge--and mushroom the edge. Hold the burnisher in two hands, and run it down the edge away from you with some pressure on it, three or four times. This will flare the edge a bit. Now proceed to put the left and right hooks on the edge, as you normally do. By the way, I agree with Mark Singer and others who say that it's cool to have a heavy hook and a lighter hook.

In addition to mushrooming the edge, the other main key is to have a really well jointed and sharp edge. I think after your jointing step with the file, if you could sharpen that edge with an extra fine (~1000g) diamond stone or 800-1000g water stone or india stone you'd be in great shape. If you have a square edge on your bench, lay the scraper flat on the bench, and hold the stone up against the edge of the bench, so that the stone makes a right angle with the bench top. Then run the scraper edge along the stone surface to sharpen the jointed edge. If you find this helpful, you can even hone finer using the same technique--the sharper the edge, the better the hook, and the finer the lace, as others have said.

Wiley