Polishing a homemade blade

K

Kevin Granlid

Joined
Nov 7, 2021
Messages
9
Hi. I'm making my first ever knife and i am now trying to polish the blade. I have sanded it by hand from 180 grit up to 2000 and then buffed it with Autosol but i can still see scratches. How do i get the scratches out? Do i just have to start over from 600 grit and juist spend more time sanding or is there any other way.
 
Personally I'm not aware of any other way of superceeding the refinement of the scratch pattern, but others know more.
 
If you still see scratches, then you simply haven't removed them with one of your successive grits. You'll have to go back to a lower grit and keep working it until the scratches you are seeing disappear. It can help to change your angle as you are sanding so that you can see the previous grit disappearing more readily. When all of your scratches are running the same direction, it's harder to see when you've completely polished them out.
 
The higher the grit you go, the slower you'll remove metal. If you still have scratches from 180 grit, those are very deep scratches, technically you can eliminate those scratches will a 2000 grit sandpaper, but it will take a long long time, and you will go through a lot of sandpaper, maybe days of handsanding.

When you start from a low grit, 180 grit, and you go to 220 grit, you make sure that you have eliminated all the scratches from the 180 grit, because 220 grit can remove 180 grit efficiently. Repeat for higher grit. The reason Nick Wheeler tells you to go alternating 45deg is so that you can make sure you have eliminated all the scratches from the previous grit, if you just sand in the same direction, the previous scratches will hide in the current scratches.

I made a similar mistake with my very first knife, I finished the knife on a 36 grit belt before heat treat, you didn't read that wrong, 36 grit before heat treating, after heat treat, the scratches are to damn deep that it's impossible to grind out even with a belt grinder, I was still optimistic that I can hand sand everything, I went for days and wasted tons of sandpaper with little to none progress.
 
Thanks for all your help guys. I did bring it up to like 1500 grit before heat treat. But i was probably a bit hasty with going up the grit.
 
Also, contamination from a coarser grit can cause this. Everything must be clean after 1000 grit. Clean the sanding area, change the paper towels and anything that was in contact with the last grit. Wash your hands and the blade before starting the next grit.

Another issue is galling. This is caused by the swarf balling uo into tiny balls and acting as a much coarser grit. Dry sanding, not changing the paper soon enough or excessive pressure while sanding can all cause galling. The common symptom of galling is "J" hooks, which are lines that go down the blade and then curve and reverse at the end of the line. Do the final strokes as a long stroke from ricasso straight off the tip of the blade. Lift the paper or polish media and return to the ricasso for the next stroke. Don't sand back and forth. That is a good rule for most all sanding work beyond 400 grit, including polishing.

Personally, I do not polish blades. It is impossible for a polished surface not to get scratched in use, so the look will be destroyed soon anyway. A nicely done 600-800 grit satin finish looks and lasts much better to most folks.
 
PMQ said:
I made a similar mistake with my very first knife, I finished the knife on a 36 grit belt before heat treat, you didn't read that wrong, 36 grit before heat treating, after heat treat, the scratches are to damn deep that it's impossible to grind out even with a belt grinder, I was still optimistic that I can hand sand everything, I went for days and wasted tons of sandpaper with little to none progress.
Click to expand...

I feel your pain, I did pretty much the same thing. Now hand sand to at least 320 or 500, then heat treat.
 
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