Thread: Belt Progression

Before I start my next project, I'm going to order in a few belts for my grinder, but I thought I'd check what you guys use first.
I'm talking about what grits you like to use for both before and after heat treat grinding.
When I'm hand sanding blades I take small jumps in grit, but I'm guessing the jumps can be greater when grinding.
Thanks for any input fellas.
Grant

Hey Grant,
On stainless i rough out in 80 grit. Then go to 180, 240, 400, 600. Then i usually start handsanding at 600, go to 800 and then heat treat by a pro in a vacuum furnace. No scale - just minor oxidation.
After heat treat i usually avoid the grinder if at all possible and start back at 600 hand sanding and go up.
With carbon that i heat treat myself, same progression prior to heat treat. i do not want any deep scratches that may cause stress risers. i do leave more meat on the edge to allow for scale removal and decarburisation.
Then i re-start at 400, then 600. Then start hand sanding at 600 and go on up.
As always, there is definitely more than one way to skin a cat, but with any of them the skin has to come off.
Hope that helps.
Adam

I have not found the perfect progression or perfect belt selection yet, for now

60-220-400-800-hand sanding

I am curious to see what others use

Charlie

I agree, I still play around with a lot of different belts and grit combos. That being said:
60, 180, 400, 600 before HT
180, 400, 600, 800'ish then hand sand depending on the razor.

Honestly, I think it's a lot like honing, everyone use a little something different but most have a similar end result.

I usually go 40 80 120 240 400 600 800 and then handfinish with some wet dry paper.

Is there a reason for finishing to a high level such as 600 or 800 grit before heat treating? If the razor was heat treated after grinding with say 180 grit, would the HT somehow be negatively affected?

I have only used carbon steels (forging, no stainless) and haven't yet made my first razor, still studying up a bit... On the knives I've made, the belt progression I use is: 50, 120, then heat treat. If I left a fair amount on or want to slightly change the profile, I'll go back to 50 grit, then on up to 120, 220, and finally 400. I have some of the J-weight 220's along with regular ones for the flexibility they offer in getting around small curves. I'm using Deerfos belts and like them fairly well. After the 400, I hand sand from there.

MattW-
I'll preface what I say about your question with I think it depends upon the steel being used and the individual maker's process. Someone using stainless steel that can heat treat it at nearly finished dimensions with foil or anti-scale compound will have less work to do on a blade after the steel's been hardened. My process, on the other hand, using carbon steel and quenching in oil, I need some more meat left on the blade to keep from warping as well as dealing with forge scale and de-carburization. What that means is, I'm going to need to grind more steel off after it's been heat treated. If I took all the time to go up through the grits, it'd be somewhat of a waste since I'm just going to grind through that higher grit...

That being said, Adam G. already mentioned something important-stress risers. If steel has deep scratches in it (50 grit, for instance) and is then taken to be quenched, bad things can happen. When steel is quenched, it's going through some serious stresses. If there are deep scratches in the surface of the steel, especially if it's thin, those stresses might just use that scratch to open up a crack. So, guys will take the grind to a higher grit before heat treat, to leave shallower scratches, hopefully not allowing for the cracking during the quench. I was taught to thermal cycle my steel at the end of forging (to help relieve those stresses introduced while forging into shape) and go to 120 before quenching. So far (knock on wood), no problems with stress risers or cracks during the quench and no need to go through more higher grit belts.

I hope that makes sense and is helpful.


Jeremy

I had suspected the deep scratches (high peaks and valleys in the steel) might have some effect, thanks for the explanation. I am doing some research on making my first razor from bar stock, so this is very helpful.

I go to320 on the belts and then hand finish with at least 400 before HT. Backs, tangs, and tails I finish to 1K by hand as they don't see any further grinding & working hard steel versus soft (pre-HT) will teach you that you can't really finish too high before HT. I don't do my own HT, they are done by a pro using a salt bath & there is less scaling than just open oven.

Also, doing a rough finish pre HT -> deep scratches.
Removing deep scratches after HT -> tedious.
Therefore medium grit finish pre HT -> less tedious