DIY Scraper

[thestelster]

I might be scraping some surfaces soon, so I figured I should prepare.

Made this out of an old dull useless file.

The actual scraping point is from an HSS planer blade.

Overall length is 16". I think I ground the blade a little too sharp, so it wants to carve instead of scrape.

Now to practice....a lot!

 

[Rauce]

3/16” x 1” flat bar makes a good scraper body. I cut a tang on the back and put a file handle on.

I haven’t really used HSS much for scraping, so I’m not sure what the ideal geometry is, but for carbide scraper blades you want 5ish degrees negative rake and a large radius to the cutting edge (2-3”).

 

[thestelster]

3/16” x 1” flat bar makes a good scraper body. I cut a tang on the back and put a file handle on.

I haven’t really used HSS much for scraping, so I’m not sure what the ideal geometry is, but for carbide scraper blades you want 5ish degrees negative rake and a large radius to the cutting edge (2-3”).

Thank you. I think Iground the radius too small. Easy enough to fix, and not sure what rake I put on it, but that's easy enough to remedy too.

 

[thestelster]

blades you want 5ish degrees negative rake

Can you show me a side view of your scraper on a surface so I can understand what you mean.

 

[Rauce]

Can you show me a side view of your scraper on a surface so I can understand what you mean.

Here’s a drawing from Edward Connelly’s book Machine tool reconditioning and applications of hand scraping.

The angle of (3) is how much negative rake there is. The drawing shows the blade as being double beveled, that way you can flip it when the edge on one side gets dull.

This book is pretty old so all of the advice on blade geometry and honing is concerned with tool steel .

Regarding radius, I think the typical advice is to use a larger radius for roughing and a smaller radius for finishing. A smaller radius on the edge makes for narrower scraping marks.