Getting rid of scratches?

G

gipelprup

Joined
Nov 12, 2014
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My apology if this is a repeat; not sure how the forum works. Need advice on scratch/file mark removal procedures. Would appreciate email responses, if possible. Between final bevel grinding and final finish, I have problems eradicating file marks and scratches. Also to get rid of carbon "crud" after heat-treat. I have a Scotch-Brite buffer wheel that adds shine, but doesn't remove the imperfections. Are there more "aggressive" wheels available? Where available? What are they called? Do they require buffing compound? Grease-based or dry? Anyone aware of a source of American-made (or other "quality") files? The Chinese and Mexican imports are pretty pathetic. Any advice appreciated! Tks! -- paulallen1942@aol.com.
 
Yeah the surface imperfections after heat treating wil be partly from decarb which needs to be sanded or ground off. When sanding, alternate at 45 degree angles with each grit. This allows you to see all 120 scratches when you move to 220 and so on. If an 80 or 120 grit scratch is left behind at 220, 400 or 600 will take ages to remove it. The biggest thing is just making sure every single mark from the previous grit is gone before stepping up to the next one. Scortchbrite can give a nice satin, but only if the blade has a proper clean finish first.
 
They are easy to get rid of ... you sand them away. The state of the surface before HT greatly affects the final finishing ease. If there are deep scratches and irregularities in the blade before HT, they will still be there in the hard steel after HT. It is far easier to get them out in the soft steel pre-HT. I take all blades to a good clean 400 grit finish before HT.

Most use their belt grinder to clean up the blade after HT, then switch to hand sanding with a hard block behind the paper. However, a good blade can be done with only files and hand sanding. Power tools and fancy wheels/belts are not needed.

As to your scotch-brite wheel, it will probably make getting a good finish worse. It creates minute hollow scoops in the surface, which are sort of like millions of deep scratches. Hand sanding with a backer block is how to get smooth, flat, and shiny blades.
 
There are as many tricks as there are knife makers. Diamond plates can be used for flattening and EDM stones for "rough" sanding. You can alternate between belts and hand sanding changing the direction as you go. Scotch-brite is really a finish for our purposes, not an intermediate step. A hand rubbed finish as "course" as 220 grit can look quite good as long as it is clean and even.
 
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