Lesson on sanding belts

K

KenH

Well-Known Member
Hello all - I'm posting this in the "New to Knifemaking" section because today I felt like a newbie of first order. Remember how we always say "use belts like they're free"? Today I had a petty chef profiled and HT'd nicely at 60Rc - this blade is S30V - "high dollar" (to me) steel I was trying out. It's .068" so only profile pre HT - boy was this stuff grinding SLOW!!! and having dickens of a time keeping it cool. I wound up getting too much color in bevel while grinding even though I was dipping in water each pass on grinding belt. I was using a 36 grit belt, while the belt was not new, it sure felt real rough so I thought it should be ok. Just wasn't cutting good at all. I told the wife this was because S30V is such a hard to grind steel and was easy to overheat. Well, after getting blue color on bevel while grinding a file will now cut the edge (.030" at edge).

I know I'll have to re-heat treat this blade - hope that's ok for S30V steel?

Well, to cut to the chase, I "Finally" got out a new 36 grit belt - boy did it cut, and no overheating at all! Had I got the new belt to start I'd never ruined the HT. I was thinking slow cutting was due to "tough S30V steel" rather than dull belt. While the belt was "rough", it didn't feel "sharp" the way a new belt does. I SHOULD have listened to my fingers when they didn't feel that "sharp", but only felt the "rough" of grit. Yes, I'm using AO belts because I don't really make that many knives and it seems AO give me decent life..... One belt per blade or maybe 2 blades depending on size.

Expensive part is getting Dry Ice to quench a single blade!

Ken H>

rant mode off - I've now let off frustration :).
 
Ken, I know exactly what you are speaking off. I use to do a lot of cabinet and furniture work. I had a big 4x24 hand held belt sander, it was a workhorse. I soon realized when it got down to exacting work never use an old belt as you can screw-up a expensive cabinet in a heart beat. All for a belt that costs a few dollars!!

I learned that if it wasn't cutting like I thought it should to try a new belt. There is always some use for those old belts!! Tuff luck on the knife and there is a lesson you won't soon forget. The first cabinet I screwed up cost me several hundred dollars and days of labor to build a new one!!
 
Yep, lesson's learned are usually the "hard way" by making mistakes. I knew to use sharp belts, and thought I was using a sharp belt, I could tell it wasn't cutting as expected, but thought the not cutting good was because of all the things I'd read about how hard S30V was to grind. Lesson learned: S30V isn't all that hard to grind after all - 60Rc S30V grinds much like 60Rc AEB-L does. No problem..... with sharp belts!

I've not fully decided if to re-HT or not. I've read that SS should not normally be re-HT'd. But - the S30V datasheet has instructions for "stress relieving" S30V that has been hardened, so maybe that would be ok.

Or perhaps ok just to grind back edge a bit and have a 1.3" wide blade rather than 1.5" wide blade? Not sure what I'll do just yet.

Ken H>
 
I'm bad about being overly optimistic when it comes to how sharp a belt is. Then I realize how hard I'm having to push to get it to cut. Like you say, when in doubt just go feel a brand new belt. All of a sudden "bumpy" doesn't feel the same as "sharp."
 
try a zirconia belt in 80grit, sharp enough to cut, not that much more expensive than AO. my last batch of 1/16"(0.0625") O1 knives, I ground a bevel and was about 0.03" pre-heat treat. had no issues with decarb or warping. might be something to try.
 
I've had good success with Aluminum Oxide/Zirconia combination belts from Pops. Cheap in price, but do seem to hold up a bit longer than pure AO belts. While I can profile with "not so good" belts, I want a fresh sharp belt for bevels and for working wood.

Ken H>
 
Why not profile on a bench grinder? I just did my first few on a pink wheel. It went very fast. Just asking. I had to do it that way as I don't own a belt grinder.
 
If you don't have 2X72 belt grinder, you use what you've got.... bench or side grinder.
 
David Boye wrote a whole book around making knives on bench grinders. At the end of the day, it's about the finished product regardless of how you get there.

Belt grinders sure do make life simple though.


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