Full Chisel Blog

June 24, 2009

Scrapers again

Filed under: Historical Material,Of Interest,Scrapers,Techniques,Uncategorized — Stephen Shepherd @ 5:59 pm

I have more to say about scrapers.  The mere act of cutting the blades and grinding them changes the edge characteristics of the metal and adds to work hardening.  I also suspect filing and even stoning add somewhat to the work hardening of the steel above its original hardness.  And old saws aren’t that hard which is fine, they don’t snap when kinked.

The Stradivarius scrapers are made of a particularly pitted old saw that I have cut down to make another pattern makers saw.  I don’t care about pits on the saw blade but it can cause problems on a scraper.  So all of the edges have been ground somewhat, the knife blade shapes are sharpened like knives.  The others are sharpened with a 45 degree bevel and capable of only a single burr.  But they don’t necessarily need a burr.  A rough grind will quickly scrape a surface, albeit rough.

 sharp Strad scrapers

Sometimes the best metal is under the handle and toward the heel which usually has less rust.

good steel

I am going to make a couple of 45 degree luthier scrapers and a square card scraper from the ones on the left.  The small one on the right has already seen good service.

 I also have a couple of original scrapers, the upper one is from a nineteenth century English tool chest and the other is marked OSBORNE, which are known for their leather working tools.

original scrapers

The rounding of corners is the condition that I found them.

And if it is too pitted you can always make a glue comb from the blade.  This is discussed in Hide Glue – Historical & Practical Applications on page 42.  Used for a uniform coat of hide glue on all glue joint surfaces, especially for veneer work.

Glue Comb

Stephen

 

6 Comments »

  1. Nice looking scrapers there.

    On photos of some of the old violins, you can see scraper marks under the varnish. Modern luthier scrapers tend to the thin side, so that they can be flexed while scraping — to give a very fine finish.

    Comment by Ken Pollard — June 25, 2009 @ 6:59 am

  2. Ken,

    Interesting, although I don’t know how a thinner scraper would give a finer finish? Looking at the original photograph, the two thin long ones seem to be made of old swords and appear to be much thicker than the ones I made. I need to find an old sword or two and remove the tips, well alright I need to find reproduction swords, etc.

    The two thin ones are quite flexible, but I can see how they would be more useful if they were thicker. I used one on the inside of the pitman hole for the spinning wheel restoration I am doing, and it would have been better if it had not flexed, as I imagine the originals didn’t.

    Stephen

    Comment by Stephen Shepherd — June 25, 2009 @ 9:57 am

  3. By flexing the scraper, you apply the cutting force on a smaller surface, for very focused application. One of the most challenging areas is the channel scoop on the spruce top. Following the purfling, you are cutting across grain, with tear-out being very likely. Bending and controlling the edge of the scraper, you slide across the grain, while cutting at an angle, which gives a clean finish.

    A pretty bad description, I’m sure. My previous scraper stock was 0.020″ thick. The new stuff is 0.010″ thick. Very nice. Make one. Try it.

    Comment by Ken Pollard — June 26, 2009 @ 10:15 pm

  4. Ken,

    I will have to give it a try as soon as I find some steel that thick. And if it were not for a Standard Wire Gauge I own, I would not be able to measure that thinness.

    Stephen

    Comment by Stephen Shepherd — June 27, 2009 @ 5:38 am

  5. Good stuff. Making wooden bows requires a LOT of scraper use. I usually switch between cabinet and goosneck scrapers. Scrapers are a very handy woodworking tool.

    Comment by Jonathan — June 27, 2009 @ 7:00 am

  6. […] here is the trick; I used a glue comb to evenly spread a given amount of liquid hide glue over the surface of the pine substrate, the […]

    Pingback by Hammer Veneering with Liquid Hide Glue « Full Chisel Blog — November 26, 2009 @ 7:39 am

RSS feed for comments on this post. TrackBack URL

Leave a comment

Powered by WordPress