Sharpening problems

[Shawngambrel]

hey everyone, I’m making a batch of skinner knives from 15n20 saw mill band saw blades. I annealed them and then heat treated and tempered. Does anyone find it difficult to get a good edge on them? I’m wondering if I’m making the blade to thin at the cutting edge then trying to sharpen them? It seems I can’t never get a quick edge on them. Also I know the heat treat should be good, the file skates across and I didn’t drill the holes in the tang first. It would cut with the drill bit I had to go lower in the tang to get the drill bits to go through lol

 

[milkbaby]

Maybe a sharpening issue? Possibly forming a wire edge/burr. Or a testing issue? What do you mean by you can't get "a quick edge"? A lot of people, including me, like 15N20 because it performs really well for a relatively simple steel.

 

[Shawngambrel]

Maybe a sharpening issue? Possibly forming a wire edge/burr. Or a testing issue? What do you mean by you can't get "a quick edge"? A lot of people, including me, like 15N20 because it performs really well for a relatively simple steel.

I’m using a lansky sharpener. I sharpen until the burr is found then I take against a leather belt. I can get it shaving sharp but it takes a while and seems like the shaving sharp goes away quick

 

[flatblackcapo]

I’m using a lansky sharpener. I sharpen until the burr is found then I take against a leather belt. I can get it shaving sharp but it takes a while and seems like the shaving sharp goes away quick

Get the blade under a good strong light and look at the edge with a magnifying glass or jeweler's loop. You might have a very small burr that is causing you problems.

 

[JTknives]

15n20 will get crazy sharp with a proper heat treat.

 

[Stacy E. Apelt - Bladesmith]

IF the HT is right, you should have no problem getting 15N20 really sharp.

Check list for troubleshooting an edge problem:
Did you remove all decarb before sharpening - the bevels need to be taken down after HT … and the edge does as well. Sand the edge back a few thousandths of an inch to make sure all decarb is removed from the edge.
How thin did you take the edge before sharpening - in sanding/grinding the bevels post HT, you need to take the edge to a very thin measurement. It should be a flat area around .001" to .005", depending on the knife use.
What angle are you sharpening at - The edge angle should be right for the tasks the knife will do. For a starter angle, try 20° per side.
Is the edge ready to sharpen - The edge should be straight, decarb removed, and at least sanded to 120 grit before sharpening.
Are you killing the edge in power stropping/buffing - It is pointless to spend t=wenty minutes getting a scary sharp edge only to ruin it on a power strop or buffer. The strop needs to be charged with compound, run reasonably slow, and only contacted lightly for a few passes. More than that may ruin the temper in the very edge. It is better to strop on a flat strop than a power strop.
Are you getting rid of ALL the wire - an examination under a loupe or other 10X magnifier should show a clean edge with no glints ( flat spots) or pieces of the wire left. If they are there, go back and repeat the last sharpening steps again until you have a smooth and continuous edge that is hard to focus on. A good way to remove the micro-wire is to cut a couple pieces of stiff cardboard after sharpening and before checking the edge under magnification. After cutting through a piece of cardboard four or five times, the edge should slice a sheet of printer paper effortlessly with no drag or skip.

 

[KnuckleDownKnives]

I use some of jt’s 15n20 from saw mill blades and have taken my blades to 0 before sharpening and the get super crazy sharp.

 

[Don Hanson III]

The steel isn't the problem.

 

[Ken H>]

Also I know the heat treat should be good, the file skates across and I didn’t drill the holes in the tang first. It would cut with the drill bit I had to go lower in the tang to get the drill bits to go through lol

Are you SURE about your HT? In your post it seems you said you could drill the tang with a drill bit? If so, that doesn't sound very hard.

 

[Don Hanson III]

Steel could have been overheated in the heat treating procese.

 

[Stacy E. Apelt - Bladesmith]

To add more about the HT ...
A file skating on the edge indicates very little. Even pearlite can skate a file. A blade at Rc50 could likely skate a file. And, conversely, a blade with decarb from a forge HT may file easily at the edge .
Yes, I do the "file test", as most folks do, but I don't panic when it bites in. Grind the edge back about .005" to .010" and it should be fully hard and good steel.

I was at a newer smith's very basic forge last year and he had just done a HT. He hit it with a file and exclaimed that the HT failed again. He said most of his HTs were easy to file the edge, and the more times he re-did the HT the worse it got. He was positive he had been sent bad steel. He showed me six knives in a bucket that were all "Bad". I took one out and went to the grinder (a HF 1X30, but it was all he had). At first it was like grinding mild steel ... virtually no sparks. A few seconds later there were showers of intense sparks. I told him he had to grind past the decarb to get to the good hardened steel. We re-ground the edge and bevels on every blade and all were fine. The other issue was he was forging the blades with a two-brick forge and doing fifty or more heats to shape the blade. With all the overheating and re-heating he had a serious layer of decarb on the blades. I explained that every carbon steel blade needed to be re-ground/sanded after HT. I showed him how to cycle the blades to repair the thermal damage and restore the grain, and remove the high amount of RA. He had much better results after that.

 

[Shawngambrel]

Well I believe it was burr issue I took a leather belt and increased the angle I was stropping it with. Now in just a matter of seconds it’s shaving sharp like crazy

 

[skillgannon]

To add more about the HT ...
A file skating on the edge indicates very little. Even pearlite can skate a file. A blade at Rc50 could likely skate a file. And, conversely, a blade with decarb from a forge HT may file easily at the edge .
Yes, I do the "file test", as most folks do, but I don't panic when it bites in. Grind the edge back about .005" to .010" and it should be fully hard and good steel.

I was at a newer smith's very basic forge last year and he had just done a HT. He hit it with a file and exclaimed that the HT failed again. He said most of his HTs were easy to file the edge, and the more times he re-did the HT the worse it got. He was positive he had been sent bad steel. He showed me six knives in a bucket that were all "Bad". I took one out and went to the grinder (a HF 1X30, but it was all he had). At first it was like grinding mild steel ... virtually no sparks. A few seconds later there were showers of intense sparks. I told him he had to grind past the decarb to get to the good hardened steel. We re-ground the edge and bevels on every blade and all were fine. The other issue was he was forging the blades with a two-brick forge and doing fifty or more heats to shape the blade. With all the overheating and re-heating he had a serious layer of decarb on the blades. I explained that every carbon steel blade needed to be re-ground/sanded after HT. I showed him how to cycle the blades to repair the thermal damage and restore the grain, and remove the high amount of RA. He had much better results after that.

Amen

 

[Michael Whipp]

To add more about the HT ...
A file skating on the edge indicates very little. Even pearlite can skate a file. A blade at Rc50 could likely skate a file. And, conversely, a blade with decarb from a forge HT may file easily at the edge .
Yes, I do the "file test", as most folks do, but I don't panic when it bites in. Grind the edge back about .005" to .010" and it should be fully hard and good steel.

I was at a newer smith's very basic forge last year and he had just done a HT. He hit it with a file and exclaimed that the HT failed again. He said most of his HTs were easy to file the edge, and the more times he re-did the HT the worse it got. He was positive he had been sent bad steel. He showed me six knives in a bucket that were all "Bad". I took one out and went to the grinder (a HF 1X30, but it was all he had). At first it was like grinding mild steel ... virtually no sparks. A few seconds later there were showers of intense sparks. I told him he had to grind past the decarb to get to the good hardened steel. We re-ground the edge and bevels on every blade and all were fine. The other issue was he was forging the blades with a two-brick forge and doing fifty or more heats to shape the blade. With all the overheating and re-heating he had a serious layer of decarb on the blades. I explained that every carbon steel blade needed to be re-ground/sanded after HT. I showed him how to cycle the blades to repair the thermal damage and restore the grain, and remove the high amount of RA. He had much better results after that.

Hi Stacy, Concerning the file skating. I'm working with 1084 and I sand away the decarb then check with a file. It has that skating sound but still leaves scratches. I sand away those scratches and try again. I'm sure I'm through the decarb but the file still bites, not much but still leaves scratches . Should the file not leave any marks at all if it's properly heat treated? I'm using a paint can Forge that easily get it to non magnetic. After testing for non magnetic I put it back in the Forge for only a minute or so then quench in peanut oil that's heated to 120/130 degrees. I also have a set of the Japanese hrc files coming in the mail in the next day or so, do you have any thoughts on them?

 

[Stacy E. Apelt - Bladesmith]

It depends, but yes. A good new file can be RC 67-70. Hardened 1084 should be Rc 64-65. You are listening for the sound more than looking at the marks.

 

[Michael Whipp]

That's good to hear, thanks. It's definitely making the skating sound that I've heard in a bunch of videos. And I'm using a nice new old stock hand saw sharpening file.