Australian/New Zealand Luthiers Forum

Everyone has their own way off burnishing a scraper. Some work for you, some just never seem to. The scraper material has a lot to do with it. I like the Sandvik/Bahco ones. The secret is in having a steel alloy that is basically fairly soft, but which work hardens rapidly if it is deformed. So when you sharpen a scraper, the first thing to do is to file back to soft metal, get the edge clean, smooth and square and then you can start with your burnisher, which deforms the relatively soft metal and turns a hard burr. My tool of choice for this process is the Veritas variable angle burnisher, which does a great job and you can easily create a pile of shavings that look much like plane shaving and almost as fast. However, using the burnisher means you have to hold the scraper on edge in a vice, without damaging the opposite edge that you just burnished and this gets to be a problem when you've worn your trusty scraper down a bit. Faced with this problem I came up with a solution comprising a stick and an old solid carbide router cutter (with the business end ground off). It works just like the guts of the Veritas burnisher, an obliquely mounted shaft of tungsten carbide. The angle of the burr you put on the scraper depends on the "angle of dangle" of the stick. For this tool, if the stick is vertical, the carbide shaft is horizontal, so there is no "roll" angle when it is dragged over the scraper. When the handle angle of dangle is about 30 degrees from the horizontal, the burnishing angle is about 10 degrees. This tool works really well for those narrow scrapers. It would work even better if the 1/4" carbide shaft had been 1/8th inch, so when I have a worn solid carbide 1/8" shaft cutter I'll be mounting it in a nice Jarrah handle. The carbide shaft inside the Veritas burnisher is 1/8".

Another neat idea I saw on some website I can't remember (so apologies to the guy who came up with this one) is to mount the inner race of a small bearing on a shaft and then roll it down the scraper edge, burnishing both corners at once. This works OK, but not as well for me as the stick burnisher. The shaft the bearing race is on is 10mm diameter. It would work better the smaller the bearing. 6mm is likely too small (you'd risk bending the shaft), 1/4" you might just get away with, otherwise 8mm.

If you haven't mastered scraper sharpening, stick with it, because a scraper is the "go-to" tool for those gnarly jobs.

Thanks for that Trevor, I'm one of those struggling to get it right , I'm now off to the shed to find that nice little piece of Jarrah for the handle

Is this the scraper you use?


http://www.highlandwoodworking.com/bahc ... raper.aspx


How important is it to use a hard burnisher eg carbide versus something handy like a HSS drill shaft or screwdriver?

Matt, Trevor will probably chime in but till he gets here..the steel in the burnisher must be harder than the blade you are putting the burr on (burnishing) and a screwdriver won 't cut the mustard, too soft.

Steve

If you have a good scraper (hard steel) you will find that it will cut into the shaft of most screw drivers etc. Do yourself a favour and get a good burnisher if you are going to use a scraper.

I bought the veritas one as Trevor shows, and I think it's a piece of crap. Ended up getting a round one on a nice handle and it's a dream to use.