Knife polishing (12c27) - mirror look

R

Revan03

Joined
Jan 28, 2023
Messages
4
Hello,

I always wanted to do some knifes by myself and recently I started. I slowly learned, how to do basic shape, grind edges on belt grinder.

I use for my knifes steel 12C27 and I am satisfied with this steel. Currently, I am struggling with final polishing to mirror. I would like to ask more experienced knife-makes for advice.

How to do that mirror shine?

My steps:
1.) Grinding with belt grinder in jig using cubitron belt grit 60 - rough shape
2.) Still in jig using Trizact belt with renctagles grit 220
3.) SStill in jig using Trizact belt with renctagles grit 400
4.) Still in jig using Trizact belt with renctagles grit 800
5.) Hardening


6.) Surface is already not so bad and my thinking to finish was:
- Use belt grinder again with belts to grit 1000 and finish again in belt grinder with felt belt and paste chromax an as last felt belt with paste titan extra
- Result is not good, hold knife in hand in exact angle using tin belt grit 1000 is difficult to me and surface is not homogenous. Polishing paste does not stick to felt belt much, definitely I did not get mirror shine


- I tried also hand grinder (something like dremel) with 3 leather discs and paste instead of belt grinder and I am also not happy with result, there are still scratches, which I am not able to get rid of.


- I tried to do that just with sand paper, bought big set from grit 800 to 7000. Took a lot of work but at the end, seems to me, that there are still visible scratches from first 800 grit sand paper


I invested to felt belts to belt grinder, than to leather discs and big set of sandpapers. Definitely, I am learning and probably not do everything good, but which way give me best result?

Also, I am little-bit lost with amount of polishing disc types and paste types. Please can you advice which equipment to buy to get good result?

Thx.
 
I don't know the cure, but I can tell you that 12C27 definitely has a tendency to "orange peel" in final polishing, and it can be difficult to get a really good finish. It's not impossible, I've seen this alloy take a good shine, but a lot of makers simply give it a satin finish and call it good. Hope you find some good info. Aside from that issue, this is a really good all-around blade steel.
 
Careful hand wet-sanding up to 2000 grit or higher and then buffing on a 6" to 12" buffing machine in several steps in compound (black - red - green) using a separate wheel for each polish grit is what many folks do. A Dremel will not work!

Personally, I prefer a good satin finish at 800grit over a mirror polish that will be ruined the first time you use it.
 
Hello guys,

thank you all for advices. Ok I will try with this buffing. Maybe, I bought wrong compound for buffing. I used leather disc and compound titan extra "grey" and after that compound chromax "white". Maybe I screw up with this. I had a feeling, that after this grey compound surface is worst, but was difficult to judge. I was not sure, if this scratches were done by this compound or was there from beginning and compound just show them.

Can you advice some good buffing set with discs and compounds? There is also many types of leather discs and for me difficult to choose correct one.

Thank you one more time.
 
I don't mirror polish, but Dialux has orange paste which is apparently made for prepolishing of stainless steel.

Also, good handsanding technique and good sandpaper from one producer to be sure in your grit progression is vital. If you haven't watched yet, watch Nick Wheelers handsanding video on YouTube.
 
Looking at the picture, you have some marks that wern't sanded out with the coarser grits and that makes it hard to get them with the finer ones.

When hand sanding metal I sand at 45 degrees while working through the grits and alternate the direction so you can see the marks from the previous grit are gone before changing direction with a finer grit. Final grit is used straight along the length of the steel.

I have some mass produced kitchen knives and in the right light you can see they were finished across the blade and not down the length of it.
 
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