Making a straight edge

Making a straight edge

Postby HenryP » Sun Mar 25, 2012 12:12 pm

Here's my latest endeavor - an attempt at the dark art of scraping, towards another first attempt - building a benchtop milling machine. Started out with a 2 1/4" x 1 1/4" bar of iron from Speedy Metals. The first pic is cleaning up and shaping it into a rectangular bar.
The second is milling a 60 degree bevel that I plan on using for fitting dovetails.
The third shot is of the bar shaped,and ready to get started on the scraping. Made the scraper from a piece of 3/16 x 5/8 cold rolled. Silver brazed a carbide tip into a notch milled in the end. A file handle completes.
Will report on progress. Henry
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Re: Making a straight edge

Postby Phil Morris » Sun Mar 25, 2012 5:55 pm

Really cool. So you scrape the ways on your milling machine with the scraper and check your progress with the straight edge?

Phil
Last edited by Phil Morris on Sun Mar 25, 2012 8:25 pm, edited 1 time in total.
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Re: Making a straight edge

Postby HenryP » Sun Mar 25, 2012 6:40 pm

The plan is to mill the mating surfaces, then use the straight edge as a reference to obtain a truly flat surface to mate against the other truly flat surface. We'll see how it works. Henry
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Re: Making a straight edge

Postby HenryP » Wed Apr 18, 2012 11:51 pm

An update on my scraping experiment. First the Prussian blue was really difficult to see, so I found some red spotting dye. It shows up with much more contrast.In the first picture I spread it on the plate too thick with a resulting thick coat on my workpiece.The last pics show the piece getting there. Also found that when I first ground the scraper I put too small of a radius on the tip.Flattened the radius to almost straight and works much better.Also got a more polished edge by spraying WD40 on the diamond wheel while sharpening. After my first sharpening, the edge had a burr, undetectable by the fingernail test but it left noticeable scratches on the workpiece. This is a slow process and I'm just putzing with it a little at a time. Henry
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