Flat Sanding, Scale Removal and Surface Grinding ??

Normark

Normark

Joined
Nov 7, 1999
Messages
6,651
Hey Guys..

How do you guys get the Scale off your blanks ??

I flat sanded one side of a blank tonight on my platen using a magnet,, and HOLY Smokes does that take forever..I screwed around with that for at least 20 mins and still didn't get it all off using a 37 Grit belt...

Would it be more cost effective to have them surface ground ??

I'm using 440C which has a heavy scale on it...

Any ideas guys ??

ttyle

Eric
O/ST
 
If you have an angle grinder I'd suggest hitting it with that first, then flatten everything out on the grinder. The oxide is much much harder than the steel but the angle grinder takes it off no problem.
 
You'd be better off using pg ground steel.when i use mill steel,i first rough profile then remove scale.less to remove this way.
 
If you do not have a surface grinder then no it would not. Even if you do it will take as long or longer to get it flat and clean. You are trying to remove chromium oxide which is very hard. I would suggest going to a different belt maybe a trizact (3-m) or similar. The bubble alumina is made for removing scale also. If you have a milling machine then a nice carbide single point mill would be the ticket.
 
Hey Guys...

Jared....

Yaa the angle grinder will make a mess of things..I wrong move with it,,and a nick and you'll be sanding forever....


Bali..

Yaa maybe that the ticket...

Most of it will be under the scales, some will be ground off,,so Yaa maybe thats Exactly what I'm going to do...

I'm always afraid of hitting the hollowgrind and F-ing the grind up,, but I guess if I'm careful and if I do it before the grind is done it'll be fine..

Thanks guys

Eric
O/ST
 
I know this works on forged blades not so sure about stainless.... but have you tried soaking the blade in vinegar?
 
I use a 60 grit and grind the mill scale off using the contact wheel. Builds heat but works much better than the platen.

--nathan
 
Eric are you talking about mill scale - or heat treat scale?

Either way, on a 36 grit belt, 20 minutes should go all the way through a 3 foot bar from one end to the other, nomatter how hard the blade or scale is.

It might go slower if the belt is really worn though. A 60 grit ceramic belt should clean the scale off in seconds.

Rob!
 
I use an angle grinder for rough work, but if you are using the belt grinder, use a contact wheel and run the knife blank same ways as the belt, instead of perpendicular to it for the flats. Then switch to the platen to flatten it out.

I don't know what kind of belt you're using but it's possible you aren't using enough pressure, a 36 grit belt should be really hogging that scale off, if you don't use enough pressure on some belts it won't fracture and stay sharp.
 
I'm not sure how it will work on the oxide on stainless, but on carbon steels sodium bisulfate (jeweler's pickle) works really well. You can buy it at hot tub and swimming pool supplyplaces as "PH Down"
a s it is used for lowering the PH of swimming pools
Oh yes, use good ventilation, and do not get anything copper in your container, or you will copperplate your steel
-Page
 
Never had a problem using the platen to remove scale from flats. Switch to the glass to do finish grits. If I ever hang my disc off of a motor, I'll switch to the disc for flats.
 
Deep scratches that 36grit leaves behind can be a b1tch to clean up, so be careful :)
Don't use it anywhere close to when you approach finishing stages.

Removing the scale is not the matter of grit size but that of grit's hardness. Try ceramics.
 
I have used 3m 977F belts for a few years now and have good luck with a 36, then 80, then 120 or trizact 300 to quickly take off the outside 2 thousandths to get down to alloy that hasn't been oxidized. A quick wipe with gun blue will tell you where to grind more.
 
Normark said:
I'm using 440C which has a heavy scale on it...
Click to expand...
Just how heavy is that scale? Is it from the forge or oven during HT? While it's been a long time since I used 440C, the other SS and carbon I get with mill scale isn't all that thick and grinds off pretty easy. It's the heavy scale that builds up from forging (or HT'ing) that gives me problems.
 
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