Removing Mill Scale

James Terrio

James Terrio

Well-Known Member
I'm working on a batch of 12 blades cut from CPM154 barstock. I profile them first, drill my holes and then comes the not-so-fun part... I'm going thru a lot of belts just getting down to bare steel. (Granted, I'm using cheap belts, waiting for a tax refund to stock up on good ones) It grinds real nice after that but sheesh, working on a dozen at a time, this step seems like it takes forever.

Short of having my barstock surface-ground by a machine shop, which would be lovely but sounds expensive, is there a better/faster/cheaper way to remove the mill scale? I seem to recall reading something about etching to help break it down but my search-fu has failed me. :(

Also, should I get the scale off first before drilling to help my bits stay sharp longer? That seems to make sense now that I think of it.

Incidentally, I'm not griping about the CPM154; I like working with this stuff and have had the same scale issues with others like D2, 1084, 440C, 1095... etc.
 
James, my search-fu work much betta than you. :D

From what I've read, soak your blank overnight in vinegar (it may take longer...maybe up to 36 hours if the scale is bad), and then you can scrub the mill scale off with a scotch brite pad. You can use something stronger, but fumes are no good, and you have to watch it to know when to take it out. Vinegar is cheap, and it works slow so you don't go too far without knowing it.

I've got to give it a try some time. My current method involves dull 36 grit belts (yuck :mad:)Throw a blank in vinegar overnight and let us know how it goes!

--nathan
 
Nathan is correct.

I did the vinegar trick and worked great. Just make sure and wash off outside with a hose and not in your kitchen sink.....Your wife will yell at you....LOL

Best of luck!

Chris

silver_pilate said:
James, my search-fu work much betta than you. :D

From what I've read, soak your blank overnight in vinegar (it may take longer...maybe up to 36 hours if the scale is bad), and then you can scrub the mill scale off with a scotch brite pad. You can use something stronger, but fumes are no good, and you have to watch it to know when to take it out. Vinegar is cheap, and it works slow so you don't go too far without knowing it.

I've got to give it a try some time. My current method involves dull 36 grit belts (yuck :mad:)Throw a blank in vinegar overnight and let us know how it goes!

--nathan
Click to expand...
 
Vinegar is the key. If you want to speed up the process, heat the vinegar.
 
silver_pilate said:
James, my search-fu work much betta than you. :D
Click to expand...

This why humbre grasshoppah come to the masters! *bows deepry* :p

Thanks for your answers guys, that makes sense. Don't have any vinegar on hand but I took one for the team and finished off a jar of pickles last night!! I'll drop a chunk in the leftover juice and see what happens.

If it works I can charge extra for my special "pickled steel" knives, right?!? :D

Vinegar is handy stuff in the knife shop. Good for forcing patinas and making cool stains for maple, etc. I'll be sure to pick up a big jug next time I'm at the grocery store. I know about stronger acids and have the scars to prove it; I used to work in a chemical plant. I avoid them whenever possible.
 
I just pickled mill scale off some 5160...I put them flat in a 9x13 pyrex pan (one that doesn't get used often) let it sit for about 24 hours, scrubbed it off with a stainless steel wire brush. Worked like a charm. Like Chris mentioned, don't do this in the kitchen sink.

Two more tips...DO NOT do this in uniform 5 minues before departing for work (splashes) and DO wear latex/nitrile gloves (soaks into the skin)! I went to work smelling like a.... well, I went to work smelling like vinegar, let's put it that way! If I had thought about it for a minute I could have avoided smelling vinegar on my hands for two days! :D -Matt-
 
Plain old cheap white vinegar. After using it strain it thru a coffee filter (not in the coffee pot) to get the bits of scale (iron oxide) out of it so that it will last longer. Neutralize the vinegar with baking powder mixed with water or Windex with ammonia or 4 to 1 water to ammonia (I think that is what Mickey Wise said at Batson's).
 
I forgot to thank you guys

Thanks guys! I filled up a glass jar with blanks, filled it with plain white vinegar and left it for about 24 hours. Scale comes off EASILY now!

I did try the old pickle juice too but it's too watered down, didn't do a thing.
 
This sounds good, but it's not going to get the low spots or pits out of the steel. Aren't you still going to have to put in on the grinder. I've been using 36 grit Blaze belts and they last a long time. I taper all my tangs too, so I'm grind off a lot anyway. I really think the Blaze belt make a huge difference. I actually save money because they last so long.
-John
 
You're right John, there are still minor pits in the steel which have to be ground out. But it really does save bunches of time by making the bulk of the tough scale come off very quickly. The CPM154 I'm using grinds real nice once the scale is off.

As long as I can afford a $2 jug of vinegar, I'll never grind barstock again without "pickling" it first. It really does help that much. Most of the scale comes off with a few quick wipes with SC sandpaper by hand!

I believe you about using good belts, as well. Got a little budget boost recently courtesy of Uncle Sam (tax refund) and will be stepping up to high-quality belts instead of the Craftsman AO junk I've been struggling with. The prices I'm seeing on Tru-Grit and SuperGrit are barely anymore than what I pay at Sears, and they can't possibly wear out any quicker, so I'm pretty confident it will save me money/time.
 
I have found that Tracy has a wider selection of Blaze belts and at a closer margin of profit. I have not used any ceramic blets other than Blaze and would like to know how they compare.
I had bought a good supply of Blaze belts before I left on my "Around the North East Tour". I sold every one I had and now am waiting for a resupply so that I can finish my knives for Blade. Boo Hoo!!cry me a river 1pup22thumbs
 
I would pickle and grind your steel before drilling the holes otherwise I believe you could end up with holes that are not perpendicular to your blade. Dan
 
This is off the subject but is another use for white Vineger.
If you get epoxy on your hands wash your hands with vineger while they are still stickyand off comes the epoxy
 
Wayne, I'ma be ordering some ceramic belts but never used Blaze's so I couldn't really compare. Good point, Dan, I hadn't thought of that. I'm no machinist but I do try to keep things straight, flat and square. Going to be ordering a nice new platen face for my lil grinder this week, can't wait to get it. Dave, I didn't know that, either! Sounds like a good tip.

Thanks again fellas! This is why I love this place.
 
Last edited:
I always grind a hollow in the handle (whether I'm tapering the tang or not) and pre-hollow grind the blade before I grind the flats, so there's not that much flat to worry about. Of course, this could be because I cannot stand the smell of vinegar...
 
You must log in or register to reply here.
Back
Top