Weird Shadow...

M

mtnsct

Joined
Jul 31, 2006
Messages
62
I was putting the final edge (DMT diamond stones and final pollish w/ Spyderco ultrafine ceramic) on a scandi grind O1 utility and when I started the polish w/ the ceramic stone a funky shadow began to appear in the middle of the bevel. Is this burned steel from final grind? It is difficult to determine exact color but to my eye it is a blend of slight grey brown to a hint of blue under low magnification.

Can over heated steel have discoloration under what appears to be clean HT'ed steel ( finished to 400 grit) only to show up after polishing?

From my limited experience I've thought discoloration from over heat during ginding was due to decarb and exposure to atmosphere; something that was only a few thousandths thick and ground off with another pass or two.

I have gone back several times to course grit on the diamond stones and work my way back to ceramic polish, have the shadow immediatly disappear with the course stuff only to have it reappear with the polish.
I am developing a slight pshycosis with this one.:confused:

Any help would be appreciated.

Rod
 
First, How did you HT your blade?

To be honest with you it sounds like a temperline or Hamon. The funny looking line is the transition from martensite to pearlite.

Chuck
 
Hi AC,

I don't think it's a hamon. I ht in an Even Heat elect. oven and do an interrupted quench in Brownells' tough quench oil with complete immerssion. It's just a strange discoloration in the middle of the bevel about 3/8" long. i don't know how else to explain it.
 
Do you forge or do stock removal? I do not think it is an over heating problem. Usually overheating lookslike cottage cheese after the HT. I had a student that overheated during HT and the tip was the only part effected. Just real blotchy looking. I have had lines in and above the hard area before. Could be many things, alloy banding (usually occures over a larger area), to even an impurity in the bar of steel. is the discoloration thin or wide? Pictures would be helpful. Probably will not cause a major problem.

Chuck
 
Hi Chuck,

I use stock removal. I get my steel from Crucible so I would assume it is clean. I'll see about getting a picture up today.
 
looks like a quench line to me. How long did you leave it in the oil before you pulled it out? maybe the middle of the thick part didn't cool below the nose of the curve......Oh, Kevin!!!! any comments? lol
 
Ok... So I had the same thing crop up with an A2 blade in the same place at the same time, during final hone. ...Well Duh!..The goofy discoloration is nothing more than rust/patina from my sweaty little thumb pressing on the newly polished bevel whilst sharpening the other side. I hadn't had this problem before since I was using oil when doing my final hone.

The instructions w/ the new Spyderco ceramic stone said no oils were needed, just water, so thats what I used to clean the stone.
I threw a little baby oil on the ceramic and problem solved.

Thanks for the help Guys. I'm a slow learner...but with your help I'll get it someday!

Rod
 
You must log in or register to reply here.
Back
Top