DId I ruin the steel

R

rkwalker

Joined
Oct 20, 2002
Messages
91
Was working on my first knife after lots of practice. Using stock removal and flat grinding on O1 steel. Had what I thought was a good flat grind went from 80 to 220 to 400 grit. At 400 I saw a couple of small flat spots on blade so decided to go back to 220 as I was grinding blade started to look wavy. Kept grinding to get rid of wave, after a while and getting to point I ruined my ridge line took a break and went outside. Heres the problem. In the sunlight Blade appears to be very stained and looks wavy but feels very flat. The staining is throughout the blade on both sides giving the blade the wavy look. Staining looks like hamon or water staining but is densily patterned. Did I change the structure of the steel by overheating as I was grinding (this never occured on any of my practice pieces). Don't know if I can save this one. Thanks for any comments. Don't have a camera to take pictures.
 
Is this steel that has been already heat treated ?? If not it doesn't matter. Grinding damage will show up as color .Other than that it's difficult to judge without seeing it.
 
The heat generated from grinding will not ruin or change the grain of the steel. I grind to 120 grit and leave the edge .040 to .050 thick before heat treating, then finish grind to 400 and hand sand.
 
Knife has not been heat treated. I think blade is flat but the staining gives the apperance that its wavy. Was going to take and go back to 80 grit but was afraid of removing too much my ridge line now is going the entire height of blade and don't want to make it worse.
 
For peace of mind, if you are concerned about flatness, color it with a magic marker or Dykem, wrap a peice of sandpaper around a file or flat chunk of steel and run it down the blade a few times. It will reveal your his / lows if you have them. Grind marks plus heat marks can give an optical allusion of a uneven condition that is simply not there.
 
well, unless you were grinding so hard that the steel was brought up past forging temperatures, you haven't done any permanent damage. if you only got a straw, brown, or blue color to the steel, you may want to re-harden and temper it.

Without seeing the stains and waves you are talking about, it is difficult to say what happened, several things come to mind: if you were dipping the blade in water to cool it, and then grindingto the point that the water evaporates quickly, you may get a yellowish oxide on the surface, that can easily be taken off with hand sanding. As for the waves, does it look like an orange peel texture? sometimes that texture shows up when try ing to polish a piece too quickly, or trying to grind too quick with a dull belt. Do you have a speed control on your grinder? the finer grits work better at slower speeds.

Hope this helps
Ken
 
Will try the dykem when I get home. Will the staining or discoloring go away after heat treat?
 
The coloring is a dull grey pattern throughout blade on both sides. It doesn't appear to be burned (I've done that enough) Am grinding until I burn my thumb and then dip in water to cool off. No adjustment on speed of grinder and water does evaporte quickly.
 
New discoloring will come from the heat treat process and you will have to sand/polish it out until any scale and/or discoloration is removed and the desired finish is acheived. For now, once you are convinced it is flat...press on and finish it. Oh and show pictures....you got to get a camera! Good Luck!
 
thanks for the info guys. I will continue working on this piece instead of throwing it into my growing pile of scrap. Really would like to get this first one out of the way so I can move on to the next one because I really need the practice and am getting tired of trying to make a hunter and ending up with a skiny steak knife piece of scrap.
 
Quick update; USed dykem and blade appeared fairly flatbut staining was still there. Didn't have and couldn't find any 120 grit for belt sander to take blade back down. Got some 120 for my disk grinder and after a couple of swipes the staining appears to be gone. Will hand sand with 220 now to avoid overgrinding or overheating the blade. Now if I can just fix my ridge line I can move forward
 
You should try to normalize/thermocycle the blade before you HT. This will equalize the grain structure and remove stresses induced by grinding. If you had forged the blade then you may have to worry but it does not sound like there should be any major problems. The only other thing is the steel may actually be flawed. try the normalize then HT and try to finish it out. I had a student who had a similar experience with 52100. The tip of the knife had not been normalized properly and it looked stained. After the knife had been re-normalized (properly) looked fine.

Chuck
 
Don't think I have run across the term normalizing before so don't know what that means but will try searching. Thanks
 
Get a piece of pyroceram for your platen. It will reduce the waviness considerably.

If you didn't forge the blade don't worry about "normalizing". Just heat treat it, or have it heat treated, whatever you do.

http://forgegallery.elliscustomknifeworks.com/
Pyroceram platen liner^. round over the top and bottom edges with 220 then 400 to ease the belt on and off the liner.

Make sure your metal platen is flat before epoxying the liner on, or it could crack.
 
Normalizing is heating to just above critical temperature and then letting it cool in air. Some makers do this and cool it faster by putting it in front of a fan or waving it in the air This is what is called thermocycling. If you plan to do a differential HT the you may want to normalize/thermocycle. Even if not it would not hurt so long as you don't overheat the material.

Chuck
 
This is a little OT but I have become confused about the order of things. What order do you anneal, normalize, temper, heat treat, thermocycle, (and other processes I may be forgetting) There is lots of info about how to do each of these processes online but no one seems to list the order you do these things even in the books I've read. I know there is a difference in steps required for stock removal and forging but don't know which processes go with which.
ie.. stock removal : grind, heat treat, temper ???
forge: ???
 
The way I do it is after I finish forging I will do 2-3 thermocycles/essentailly normalizing with a little help, then do 1 anneal. The anneal that most of us do in vermiculite or some other insulating agent is not really a true anneal. Rather a slow normalizing. Then I rough grind and finish shaping the blade. I take it to about 150 grit then I mark my blade via a stamp. Then I do one more normalize/thermocycle. Then I differential harden the blade, check for straight and then temper. This is what I do. If you do stock removal then you should be starting with annealed material. The first normalizing anneal etc is not required. But grinding can set up stresses so the second normalizing is your option. If you are not sure if your material was annealed then it is a must. It helps to keep things straight in the quench. If you want more information in much more detail Irecommend getting Wayne Goddards $50 knife shop. He covers the transformations you see in the steel during heating and cooling. It is in much more detail than can be covered here and yet it can be understood unlike many heat treating manuals. It is good for stock removal makers as well as those who forge.

Chuck
 
Ok I ordered the pyroceram platen for my grinder this morning (plus a couple bricks to made a two brick forge). Think I straightened out my ridge line (better anyway). Thanks for the break down AC that helps a bit. Have Waynes book guess I should read it over and this time from cover to cover (instead of skipping over what I think I don't need) I buy my O1 in bars from Jantz. THis knife might be ready to HT. Starting another this afternoon so I can HT a couple at a time. Going to try using just a bench mount disk sander
on this one to see if it helps maintain a better flat grind.
 
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