How to prevent galling on stones?

the possum · Jun 28, 2007

Hey all. Been having this problem on and off for a long time, and finally thought I'd ask.

I'm using stones for polishing small parts (steel). I'm mostly using flat diamond sharpening stones (between 1000 to 2000 grit), and some Arkansas stones. I do this because I can't ever get the surfaces as flat as I want with abrasive papers, even glued to glass.

Just when I'm getting everything flat and fairly even in finish, I feel that dreaded scrape from particles of metal getting gummed up on the stone and leaving a deep scratch in the steel. I've tried water, but it doesn't seem to help, so I usually just polish a few strokes and wipe the stone clean with my finger. Very tedious.

I haven't tried oil yet because I don't want to spoil my other natural stones (never used oil on 'em yet) and find out it still doesn't work. Not looking forward to the extra mess, either.

So, have you guys found any tricks that could help me out here? How do you keep your stones from getting clogged- even just a tiny amount?

fdd19 · Jun 28, 2007

yeah my norton stone is all clogged up i suspect this is what screwed me over with the sharpening that and not having a variety of grits

Jeff Clark · Jun 28, 2007

The oil won't soak into your diamond hones so you could try that. I guess you just need to look for signs that the oil loosens your diamonds. You might try something solid like chalk. That is an old trick for getting a smooth surface using a file. You also might try a volatile solvent like alcohol or white gasoline.

Broos · Jun 28, 2007

Most of the knifemakers I've heard will not even attempt finishing with diamond stones - they are notorious for scratching. I don't know how well this applies to what you are doing, but check out Don Foggs site for tips on finishing:

http://www.dfoggknives.com/copy_of_index/sword.htm#Finishing

I've also heard some of them say they use windex on their stones (I just use water on my diamond plates).

Dog of War · Jun 29, 2007

Hey, Possum. Gunsmiths and machinists I've known keep non-diamond polishing stones and files soaking in kerosene, I'm sure they wouldn't tolerate any galling on a sear or other precision part. If the smell is a problem unscented lamp oil should work the same as kerosene, and unlike oil either should evaporate out cleanly if you don't like it.

Jeff Clark · Jun 29, 2007

Once a diamond hone gets well worn in produces a smooth finish.

Old CW4 · Jul 1, 2007

You can flatten out and "restore" a stone by sprinkling fine sand and water on a flat concrete surface. I use a section of the walk way beside my house. Rub (lap) the stone around with a circular motion and you'll have it flat and like new in minutes. You can also lap two stones together. I do that under a small stream of water in the sink.

the possum · Jul 3, 2007

Thanks for the thoughts, guys. I've got the finish good enough for right now, prior to heat treat. I'm saving the final finish work and cleanup for after I get around to heat treating it, so maybe in a couple days I'll get to report back with some findings.

The oil won't soak into your diamond hones so you could try that.

That's gonna be my first trial. I do have some lamp oil in the shop, and a couple unopened bottles of baby oil from when my daughter was little. I'll see if these help on the diamond stones. If I get decent results, I think I still have a small Arkansas stone somewhere I don't use much, that I may try with oil.

You might try something solid like chalk.

I didn't have any chalk handy, but I grabbed a piece of clean soapstone from the shop & rubbed it on my diamond hone. It actually made things much, much worse.

Most of the knifemakers I've heard will not even attempt finishing with diamond stones - they are notorious for scratching.

Well, I'm having the same problem with Arkansas stones, but I'm just using the tools I have on hand. Haven't gone out & bought a whole bunch of stuff to experiment with since I'm flat broke. Would like to try other options eventually.

If the smell is a problem unscented lamp oil should work the same as kerosene, and unlike oil either should evaporate out cleanly if you don't like it.

Yeah, I don't want to mess with the stink of kerosene if I don't have to. The lamp oil I have is parafin based, and if it does evaporate, it sure takes a long time.

Once a diamond hone gets well worn in produces a smooth finish.

The diamond hones I'm using are well worn from sharpening thousands of edges. They started out around 400 or 600 grit, and are now upwards of 2000 or so in the middle.

You can also lap two stones together. I do that under a small stream of water in the sink.

I have to lap my softer manmade stones, but the whole reason I'm using the diamond & Arkansas stones right now is because they're perfectly flat. However, I did try lapping two Arkansas stones together once, and nearly ruined them. It polished/glazed the surfaces to where they don't cut at all. Most of the surface actually shines like polished granite. I'm now forced to use the back/under sides of the stones.

Jeff Clark · Jul 3, 2007

Don't use soapstone. Even when you use chalk with a file you need to have a file card (like a short-bristled dog brush) to keep the teeth clean. You should have a fine toothbrush nearby to keep your hone clean.

gator68 · Jul 4, 2007

the possum said:
I'm using stones for polishing small parts (steel). I'm mostly using flat diamond sharpening stones (between 1000 to 2000 grit), and some Arkansas stones. I do this because I can't ever get the surfaces as flat as I want with abrasive papers, even glued to glass.

What kind of parts are you trying to polish? I was taught to use sandpaper on a surface plate to fit bolsters onto knives. If you're careful, you can get them flat enough that you have a hard time telling the bolsters are not integral. You have to be careful to change the direction you sand so that you are not preferentially sanding one side and making the surface slanted or rounded.

the possum · Jul 4, 2007

Gator-
They're miniature knife blades, actually. I generally work on a scale of around 6 or 7 to 1, so basically everything has to be 6 or 7 times more precise than what I'd consider acceptable on a full sized knife, or it will be obvious in photos. The blade looks pretty good with an 800 grit paper finish; things look flat and even. But the stones show how uneven it really is. Getting things truly flat with the stones makes a real difference in the crispness of the grind lines, etc.

Using regular SC sandpaper against a hard flat surface has proved nothing but an exercise in frustration. I just don't understand how it's even happening. Once I'm done with the stones, all the surfaces and intersecting lines are crisp as cut glass. But the finish left by the stones (that I own/use) is "not quite right", so I'd like to give things a final "once over" with the paper to make everything homogeneous looking.

I take a nice flat piece of 1500 grit sandpaper, glued to glass (with no excess glue underneath), and within five straight strokes across the paper all my lines are washed out and the surfaces rounded. And it's not just the edges, either. Even around my stamp on the tang, the whole surface gets dished in concave. I have no idea how that can happen. Maybe the paper just has too much "give" to it. My next idea to try was just rubbing some polishing compound directly onto a hard surface, like a flat piece of micarta or something...

Here's a close up of a polish job I was never happy with. You have to look closely at how the light is reflecting off the surface, around all the edges of the ricasso and spine, and even around my tang stamp, and you can see how hours of stone polishing were ruined with just a few strokes on paper.

gator68 · Jul 4, 2007

Hmm, I think you are beyond any help I can give.

That's a good looking mini!

If you can get good lines on a stone then I guess it is not the way you are holding the mini blade... Seems like it must be some sort of give or flex in the paper.

Since you just want to use the paper to clean up the scratch pattern, maybe you can make a "file" -- ie, wrap the sand paper around an edge of something straight, like a triangular file edge. Then fix the blade down and pull the file edge across the blade.