How To Methods for mirror polishing a forged texture knife

[maps_mackenzie]

Hey y'all

First time posting a thread. I looked high and low for a post on this topic but couldn't find anything, if this has been asked before I'm sorry!

Here goes - I'm looking to replicate a yu kurosaki senko finish. I'm not against hand sanding a knife, but keeping the forged finish and tsuchime is important to me. I'm working with AEB-L, and bead blasting at 30psi with 80grit media)

I've tried bead blasting and mother's mag polish, But was never able to got a good polish. I saw somewhere that a bead blasted then muriatic soak could do it but wanted to ask before learning safe acid handling.

I looked into in some electropolishing but achieving that in the workshop without aforementioned lack of acid handling has been impossible, but really seems best left to pros

I have a buffer, but avoid it due to the danger and it doesn't seem to get the deeper divots.

Thanks for looking!

(Edited to add specific knife steel and current bead blasting grit and psi)

 

[Evan Wilson]

muriatic is a bit harsh I would dilute it a bit 1/3 to 2/3 water if that is not strong enough could go with a 50/50 mix remember to nutralize the acid baking soda and water mix. as for the divets might try a dremel a good amount of work but should get it done for a good mirror a buffing wheel is the way, I feel not wanting to use one without riveted mail.

 

[Bill DeShivs]

Polishing consists of removing the larger scratches and replacing them with smaller ones. Then removing those by replacing them with smaller ones, and so on until the surface is shiny.
You aren't going to accomplish that with bead blasting and acids.
And, just a buffer won't do it either, unless the surface is prepared as above.

 

[Stacy E. Apelt - Bladesmith]

In a very simple description:
Finish the cleanup on the blade - bead blasting, etching, etc.
Mask off the kurouchi with heavy tape (duct tape works well).
Using a hard backing block (aluminum or micarta works well) start with 120 grit wet-or-dry paper ( Rhynowet Red Line is a good brand). A few drops of dish soap in the water bowl helps with smooth and clean sanding. Rinse off the blade regularly.
Once the surface is flat and evenly sanded, clean up before going to 220 grit. Wash your hands, the blade, and change the water bowl to avoid carrying any 120 grit forward. Do this with each grit change.
Go to 220 grit. Sand until all the deeper scratches from the 120 grit are gone. Changing the angle of sanding will show if they are there or not.
Once all of the 120 grit marks are goner go to 220 grit.
Once all the 220 grit marks are gone go to 400 grit.
Repeat with 800 grit, 1500 grit, and 2500 grit.
At this point it should have a shiny white surface. If you want a mirror polish (I hate them on a working knife because they don't last more than a few cuts), start the polishing steps with your desired polishes. Red Iron oxide or green chrome are popular.

Personally, on a knife like the one you plan on making, I only take it to 4500 grit or 800 grit.

 

[maps_mackenzie]

muriatic is a bit harsh I would dilute it a bit 1/3 to 2/3 water if that is not strong enough could go with a 50/50 mix remember to nutralize the acid baking soda and water mix. as for the divets might try a dremel a good amount of work but should get it done for a good mirror a buffing wheel is the way, I feel not wanting to use one without riveted mail.

Appreciate the info on muriatic, but also agree on that darn buffer, thing is a menace

Polishing consists of removing the larger scratches and replacing them with smaller ones. Then removing those by replacing them with smaller ones, and so on until the surface is shiny.
You aren't going to accomplish that with bead blasting and acids.
And, just a buffer won't do it either, unless the surface is prepared as above.

Totally fair, I've just been trying everything. What do you suggest, Blasting, acid, then buffing? Are there specific compounds or blasting grits you'd recommend?

In a very simple description:
Finish the cleanup on the blade - bead blasting, etching, etc.
Mask off the kurouchi with heavy tape (duct tape works well).
Using a hard backing block (aluminum or micarta works well) start with 120 grit wet-or-dry paper ( Rhynowet Red Line is a good brand). A few drops of dish soap in the water bowl helps with smooth and clean sanding. Rinse off the blade regularly.
Once the surface is flat and evenly sanded, clean up before going to 220 grit. Wash your hands, the blade, and change the water bowl to avoid carrying any 120 grit forward. Do this with each grit change.
Go to 220 grit. Sand until all the deeper scratches from the 120 grit are gone. Changing the angle of sanding will show if they are there or not.
Once all of the 120 grit marks are goner go to 220 grit.
Once all the 220 grit marks are gone go to 400 grit.
Repeat with 800 grit, 1500 grit, and 2500 grit.
At this point it should have a shiny white surface. If you want a mirror polish (I hate them on a working knife because they don't last more than a few cuts), start the polishing steps with your desired polishes. Red Iron oxide or green chrome are popular.

Personally, on a knife like the one you plan on making, I only take it to 4500 grit or 800 grit.

This is an awesome hand sanding write up, really appreciate it. But thats for the bevels specifically right? How would I get the rest of the blade to the same level of at least shiny white?

 

[Stacy E. Apelt - Bladesmith]

As a matter of practicality, you can't make the kurouchi the same shininess as the bevel. By description kurouchi is a rough finish.
You can bead blast it with several stages of finer grit or try soda blasting for removal of all the darker forge finish.

The blade you pictured appears to have bright cuts. These are done on an engine lathe or with a flex shaft. The bit that does the cutting is normally a diamond bright cut bit, or a highly polished carbide cutter. Done right and with lubrication the cut is mirror bright.