A deep scratch appeared when sanding down shaped blade

M

Musicman88

Joined
Sep 25, 2020
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Hey everyone, so I’m making this knife for my sister in law (based on the Bastinelli diagnostic) and as I was sanding the belt marks off the bevels i noticed a deep scratch near the plunge line. I started going at it with a 200 grit and it actually removed a lot of it but it also made the edge thinner on the side of the scratch. Any ideas on how to get the scratch off without thinning out the area more? It was tough to free hand these bevels on the belt grinder and no way am I touching the knife on it at this point.

https://imgur.com/a/wDFFber
 
I would use EDM stones at this stage if you don't want to go back onto the grinder.
The 120 grit is like a magic eraser for scratches like that. Then you can switch back to hand sanding. A 320 stone is an optional intermediate step.
I get mine from Congress Tool, 1"x1/2"x6".
 
Richard338 said:
I would use EDM stones at this stage if you don't want to go back onto the grinder.
The 120 grit is like a magic eraser for scratches like that. Then you can switch back to hand sanding. A 320 stone is an optional intermediate step.
I get mine from Congress Tool, 1"x1/2"x6".
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Thank you Richard those look extremely useful! In fact looks like they are golden for finishing a blade. Unfortunately there is no store that I can get them from in Cyprus and it will take about 2-3 weeks to receive them if I get them online. I will order them regardless, just want to finish the blade in time for her birthday which is under a week. I have the lansky stones for curved blades do you think that could work? 120-250-600-1200 grit
 
Nathan is talking about using the EDM stones. They erode while in use, but the resulting slurry is useful, so just keep going without cleaning.
Given your situation and the small bevel, I would just hand sand with a good backing, starting back at 120 grit until the scratch is gone
 
Richard338 said:
Nathan is talking about using the EDM stones. They erode while in use, but the resulting slurry is useful, so just keep going without cleaning.
Given your situation and the small bevel, I would just hand sand with a good backing, starting back at 120 grit until the scratch is gone
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Right, I guess I will continue hand sanding although im a little worried that the edge is thinning down on the scratch side.
 
How thick is the edge currently? It looks relatively thick and I would just keep hand sanding. For reference I’d take that size knife down to .015” or less or .38mm if you use metric.
 
Joshua Fisher said:
How thick is the edge currently? It looks relatively thick and I would just keep hand sanding. For reference I’d take that size knife down to .015” or less or .38mm if you use metric.
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Hey Josh, my thickness measurement tool is currently mia, but its thinner than lets say a penny. 😬
 
Musicman88 said:
Hey Josh, my thickness measurement tool is currently mia, but its thinner than lets say a penny. 😬
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Depending on how much thinner than a penny you may have a ways to go before I’d say it’s too thin. I just checked a penny I had and it measured .050” so with that in mind I’d be shooting for less than half the thickness of a penny.
 
I shoot for that after heat treating, didn’t know you hadn’t hardened the blade yet. Before heat treating you definitely want to leave some meat on the edge. Most of the time I harden full thickness and grind post heat treat unless I’m working with shallow hardening steels like W2 or 1095
 
Joshua Fisher said:
I shoot for that after heat treating, didn’t know you hadn’t hardened the blade yet. Before heat treating you definitely want to leave some meat on the edge. Most of the time I harden full thickness and grind post heat treat unless I’m working with shallow hardening steels like W2 or 1095
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Ok now it makes sense hehe. Due to the curvature and the intricate bevel as well as the fact that my “belt grinder” is a modified bench grinder with no table or jig, I kinda have to bring the edge as close to finish as possible before ht cause there is no way I can find my lines again so I could not leave too much meat on the edge. I work mostly with o1 and o2. I made a 1095 tanto before but with my current tools its almost impossible to get the blade to harden properly. It got hard but I dont trust it. The O steels always get me good results with the coal forge.
 
Update: after about an hour of sanding i managed to get rid of the scratch. Thanks for the tips guys. I will surely order some edm stones they look extremely useful.
 
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