Jump to content

Polishing - stone grit ranges...


Recommended Posts

Alright, so I've spent two hours working on my #8000 grit Naniwa water stone having jumped from #3000... I absolutely cannot get the scratches out. Is it simply too much of a leap? Do I really need a #5000 inbetween there?

 

EDIT: added some before and after pictures:

(LEFT: BEFORE | RIGHT: AFTER)

NOTE: This is not before and after 2 hours. The "before" image already has two hours of #8000 grit in it)

before.jpg after.jpg

 

This is after only a few hundred strokes across the #8000 stone - but I can't help to wonder if it has made even the slighteste scientifically measurable difference... I started on a rough stone - maybe #120, then #220, then I moved on to paper #600, #1200, #1500, and #2500.

I then moved on to stone #3000, and then stone again #8000.

 

There must be a better way of doing this. Faster, and more efficiently... I'd like to attempt to make a buck or two off making cooking knives, but at this rate - people will have to put up their homes for a second morgage just to cover my hourly expenses... :rolleyes:

 

Sincerely, Alveprins.

Edited by Alveprins
Link to post
Share on other sites

There are a few things here.
First there is no need for kitchen knives to be 8000 grit.
A really solid 500 grit polish is great for kitchen ware.
Next stones come in soft and hard.
A hard 8000 stone will gall the hell out of the surface of your steel basically destroying the work you've done.
While a soft stone may cut nicely.
It would be nice to see what your finish was like before you went to stones.
You have a lot of scratches that look a lot larger or deeper than 2500 paper, which would almost leave you with a mirror polish.
The thing about polishing is that each grits scratches must be completely removed before moving on to another grit.
This is why it is one at rotating angle.
So 220 is horizontal and 400 is diagonal or vertical and so and so on.
I use desktop magnified light to look at my work through and make sure all of the scratches from previous grit are gone.
Another way to see if all of your scratches are gone is to do a quick dip in ferric chloride and it will etch any of those sneaky bad boys and you will see them going against the polish.

  • Like 1
Link to post
Share on other sites

1. First there is no need for kitchen knives to be 8000 grit. A really solid 500 grit polish is great for kitchen ware.

 

2. It would be nice to see what your finish was like before you went to stones.

3. You have a lot of scratches that look a lot larger or deeper than 2500 paper, which would almost leave you with a mirror polish.

4. The thing about polishing is that each grits scratches must be completely removed before moving on to another grit. This is why it is one at rotating angle. So 220 is horizontal and 400 is diagonal or vertical and so and so on.

 

Alright...

 

1. It is my personal preference really. I have no plans to leave it mirror finish only, but I like to polish to mirror before I etch - so that I can see both the damascus pattern as well as my face in the blade. ^_^

2. I will go back to #600 and work my way back up through #1200, #1500, #2500 on paper - taking snapshots inbetween.

3. Yeah... Those appeared invisible on the #2500 though, as well as the #3000 stone. It was not until I jumped to #8000 I started noticing.

4. Will do. I simply hate doing it in the oposite angle because of my weak side... :lol: I suppose I will have to overcome it.

 

Its been years since I've made any knives, so I am sort of re-learning all of this. ;)

 

This is what the blade looks like underneath all those shiny scratches:

knife pattern.jpg

 

Sincerely, Alveprins.

Link to post
Share on other sites

If you are to speed up production, using softer steels in the san-mai "jacket" be an option. If im not mistaken, you used

20 and 15n20 steel for the damascus and "Øberg"(1.2% C) for the edge? Mild/15n20 gives a good contrast. Pure nickel/mild steel is soft and easily ground.

A belt grinder will of course help loads. I have belts from 40 to 400.. And buffing wheels may finish off the mirror polish without going through all those grits to 8000. Going from 3000 to 5000 grit seem to tip my knives from shiny to mirror when i'm not buffing.

Link to post
Share on other sites

If you are to speed up production, using softer steels in the san-mai "jacket" be an option. If im not mistaken, you used

20 and 15n20 steel for the damascus and "Øberg"(1.2% C) for the edge? Mild/15n20 gives a good contrast. Pure nickel/mild steel is soft and easily ground.

A belt grinder will of course help loads. I have belts from 40 to 400.. And buffing wheels may finish off the mirror polish without going through all those grits to 8000. Going from 3000 to 5000 grit seem to tip my knives from shiny to mirror when i'm not buffing.

Which "mild" steel would you suggest, and where to get it? It is so difficult to find anything here in Norway... :lol:

 

I've just recently set up a belt grinder, and I've got #60 and #120 belts for it (50x 2000mm). I set it up for doing the heavy grinding only, not finer stuff - but I might just have to change that. I suppose going from 40 all the way to 400 would speed things up. I don't even put an edge on the knife on the belt grinder - I get the edge from #120 stone - which feels like forever when the edge is 63HRC...

 

I will go back to paper tomorrow and work my way up to #2500 again, and then put it against the #3000 stone. From there I have no #5000 unfortunately, but need to go straight to #8000 - which I fear is too much of a jump. I don't much want to wait two weeks for a 80USD stone to arrive from Japan or the US before I continue either... :unsure:

Link to post
Share on other sites

One trick Aldo Bruno taught me that helped a lot when I wanted a certain finish was to paint the blade with layout fluid (Dykem or similar) and sand until it was all gone. It helped me a ton because the blue scratch was really visible and I didn't have to rely on the right angle of light to see if I missed one when I was two grits past it. That'll show you if the scratches you have are new from a hard stone, or if they are remnants from an earlier step. Just reapply the fluid before you move on to the next grit.

  • Like 1
Link to post
Share on other sites

Most construction steel are s235, s275 or s355. On this site you can find chemical comp. and so on:

http://www.b2bmetal.eu/en/pages/index/index/id/141/

 

Where in Norway are you located? If you live around Bergen, I can tell you where to go look for some cheap and good steel.

I used to work for a small steel supplier. If your far off, I can probably

send you some samples of some of the steel I use in trade for info about buying hammers direct from China ;) Not that I can buy one now, but who knows in the future.

Link to post
Share on other sites

One trick Aldo Bruno taught me that helped a lot when I wanted a certain finish was to paint the blade with layout fluid (Dykem or similar) and sand until it was all gone. It helped me a ton because the blue scratch was really visible and I didn't have to rely on the right angle of light to see if I missed one when I was two grits past it. That'll show you if the scratches you have are new from a hard stone, or if they are remnants from an earlier step. Just reapply the fluid before you move on to the next grit.

Wouldn't the oil/water lubricant on the paper/stone along with the grinding paste (particulates of stone/steel/abrasive) remove the layout fluid inside the little cracks?

What is the difference between using this layout fluid and simply using a permanent marker?

Link to post
Share on other sites

Alright... I think I've got my method down...

 

I've followed some advice from you friendly peeps, and made a couple of conclusions:

 

1. The scratches were indeed greater than 2500. They were in fact 1200.

2. I went back to 1200, and then went to 2500 and polished in oposite directions as so to visually see when the scratches from the previous grit were gone.

 

So, what I did was simply polish it back up to #2500 on paper using WD-40 as lubricant. When I was satisfied I had all the #1200 grit removed - I polished it in one single direction as to get all the little scratches from the #2500 in the same direction. I then buffed it to mirror polish using blue polishing paste - and then did a light etch in 30% acid sollution.

 

I can still see the scratches from the #2500 through the polishing if I get the angle right - however I got some #3000, #5000 and #7000 paper on the way from Hong Kong. I guess I will be polishing to #5000 on paper before buffing in the future.

 

Either way, I got my method down now - and it cuts down on time relative to using stones all the way. Cutting down on time = cutting down on cost for the consumer. ;)

 

Here are some before and after images for your consideration:

Before buffing:

polish 001.jpg

After buffing (side B )

polish 002.jpg

After buffing (side A ):

polish 003.jpg

 

After etching:

polish 004.jpg

polish 005.jpg

polish 006.jpg

 

Thank you everyone for all the helpful input. :D

Now I proceed to making the handle... ^_^

 

Sincerely, Alveprins.

  • Like 1
Link to post
Share on other sites
  • 4 weeks later...

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...