Learning how to do precision scraping!

This is the scraper I was heat treating earlier, along with the bottom of a spin fixture that I'm scraping as practice.
I left the scraper super hard (likely around 64HRC, I haven't checked), seems to be working nicely so far, though I think it needs more polishing... One of those times when a polished edge is the right thing for the job!

The blue dots you can see on the metal indicate high spots that will get scraped off. After they're scraped off the piece is rubbed against a surface plate thinly covered in 'spotting compound' which again marks the high spots blue. Repeat enough times and you end up with a surface that's as flat as your reference, in this case a granite surface plate.

Hand scraping is a very cool, and very old, technique. Really fun to finally get to try it out! The plan is to scrape the ways on my milling machine when I feel comfortable with the technique...

Photo by Aaron Gough on December 27, 2014.
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