Card Scrapers for Custom Mouldings

Hello All,
I've made several feet of black walnut mouldings using hollows and rounds for the bracket feet of a Penna. spice chest project. I went on to create a matching scraper out of an old saw plate to scrape those moulding profiles. My problem is that my burnisher doesn't want to turn a burr on the scraper. I'm assuming the saw plate is too hard. Can anyone guide me through the process to convert the saw plate material into a suitable scraper that will take a proper burr. I have access to propane, map gas, oxy-acetylene, a charcoal forge and my wife's kitchen oven (as long as I finish before she gets home from work!).:eek: Thanks in advance for your guidance.

William, how about using a harder burnisher like a carbide one, rather than annealing the scraper. Here's one https://www.lie-nielsen.com/product/...ide-burnisher-

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Originally Posted by William Batdorf

Hello All,
I've made several feet of black walnut mouldings using hollows and rounds for the bracket feet of a Penna. spice chest project. I went on to create a matching scraper out of an old saw plate to scrape those moulding profiles. My problem is that my burnisher doesn't want to turn a burr on the scraper. I'm assuming the saw plate is too hard. Can anyone guide me through the process to convert the saw plate material into a suitable scraper that will take a proper burr. I have access to propane, map gas, oxy-acetylene, a charcoal forge and my wife's kitchen oven (as long as I finish before she gets home from work!).:eek: Thanks in advance for your guidance.

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William, I was hoping you would get some suggestions on this subject. For myself I have never been very successful at turning a burr on the small tightly curved scrapers. I usually just use slip stones on them and try to get as close to a 90 as I can. They seem to do okay that way. I do have a small burnished that my grandpa made from a triangular file. It works to some extent, the operator has difficulty. The saw plate should work ok. I have made scrapers from saw plates, hacksaw blades and such.
Jim

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Originally Posted by Robert LaPlaca

William, how about using a harder burnisher like a carbide one, rather than annealing the scraper. Here's one https://www.lie-nielsen.com/product/...ide-burnisher-

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If the scraper isn't ductile enough then it won't form a good burr no matter how hard the burnisher is.

A typical sawplate (~Rc50) should be OK though.

I heard it both ways about burrs on small scraper blades. Some try to get a burr others don't. I can get a burr on smooth curve ones but tight curves or quirks are difficult to do a reasonable burr. So I usually go for a smooth 90.
Jim

My guess is the radius on the small bracket feet is something like a 3/8R, I would expect that for a radius along those lines a burr could be turned, although I do agree for smaller radii that 90 degrees does seem to work fine. The best burnisher are hard and highly polished..

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Originally Posted by James Pallas

I heard it both ways about burrs on small scraper blades. Some try to get a burr others don't. I can get a burr on smooth curve ones but tight curves or quirks are difficult to do a reasonable burr. So I usually go for a smooth 90.
Jim

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I go for a burr wherever possible. The cutting mechanics of a burred vs unburred scraper are completely different and I prefer the former.

A burred scraper actually cuts at a fairly low, plane-like angle, takes a plane-like shaving, and leaves a planed-looking surface behind. It doesn't cause tearout because the burr is very small and the face of the scraper therefore behaves like a very closely-set cap iron.

In contrast an unburred scraper cuts at a >90 deg angle, and leaves a duller finish.

Over-thinking things....

I usually can cut a piece of window pane glass to the shape required. Used like a scraper. When it gets dull, just cut a new edge. Stores that sell glass windows usually have a scrap bin you can get pieces out of for...FREE. I even use a piece with a straight edge as a scraper on flat work.

No "burr" required.

I was taught by Jimmy D'Aquisto on how to sharpen card scrapers to shape wood was to use a small, 5" diameter 100 grit or more grinding wheel at a approximately 5-10 degrees from square which will produce a fine burr. this only needs to be lightly touched to the grindstone to produce the burr on one side
I like this method of sharpening when I am shaping wood or scraping off an old finish of of wood
It is fast and effective, and if it was good for one of the greatest archtop guitar maker of the 20th century, it is good enough for me

I have made many a molding with a saw plate scraper with no burr. I would re sharpen it just by putting it in a vise in a horizontal position ,squeezing it a little convex,and filing the surface a little (as little as possible) to re sharpen the edge. Since these were only one use scrapers,I didn't mind the saw plate getting a little thinner with each sharpening. My moldings were too complex to try raising burrs on.

When I was working with only 18th. C. methods in public,it was the handiest way to make small moldings,and they had no machine chop marks on them,no rotating cutter head being used.

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Originally Posted by george wilson

I have made many a molding with a saw plate scraper with no burr. I would re sharpen it just by putting it in a vise in a horizontal position ,squeezing it a little convex,and filing the surface a little (as little as possible) to re sharpen the edge. Since these were only one use scrapers,I didn't mind the saw plate getting a little thinner with each sharpening. My moldings were too complex to try raising burrs on.

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Thanks for this tip George. Next time I need one of those small scrapers I'll try your method.

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Originally Posted by george wilson

I have made many a molding with a saw plate scraper with no burr. I would re sharpen it just by putting it in a vise in a horizontal position ,squeezing it a little convex,and filing the surface a little (as little as possible) to re sharpen the edge. Since these were only one use scrapers,I didn't mind the saw plate getting a little thinner with each sharpening. My moldings were too complex to try raising burrs on.

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I like that technique, I'm going to have to try it the next time I make a one-shot scraper. It has obvious advantages in terms of "shape preservation"

I should have been clearer that "wherever possible" in my previous post doesn't include complex profiles. In my experience the burr's cutting action because impossible to control once the surface is too steep (as in the sides of a bead for example) because then you can no longer vary its engagement by tilting the scraper.

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Originally Posted by george wilson

I have made many a molding with a saw plate scraper with no burr. I would re sharpen it just by putting it in a vise in a horizontal position ,squeezing it a little convex,and filing the surface a little (as little as possible) to re sharpen the edge. Since these were only one use scrapers,I didn't mind the saw plate getting a little thinner with each sharpening. My moldings were too complex to try raising burrs on.

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Ditto.

Flattening and polishing the face, as well as lightly stoning the ends, will remove the rounded edge and return it to square. You will need to lean the scraper at a greater angle, but it will cut this way.

Regards from Perth

Derek