Spyderco Sharpmaker Question: Getting a better edge on a ZT 0350

[Maniacal Pete]

I'm working on a ZT 0350 (recurve folder s30v) and I am making progress;
near mirror finish on the bevel, but it still doesn't seem to be as sharp as
I would like it to be (tested by cutting cardboard, feathering paper).

Should I be working at 40 degrees or 30?

With the sharpmaker do you need to raise a burr each step of the way?

When I switch from the corners to the flats on the tri-stones,
the knife still doesn't seem to make much contact,
is this normal?

Any other thoughts?

I have diamond through ultra fine stones.

 

[dalefuller]

Unless your 350 edge bevels match up to the SM's 30 or 40 degree angles, you're not going to make full top-to-bottom contact down the entire bevel. If you can already see some polishing taking place through the entire width of the bevel, then that may not be a problem. The other issue is that a recurve blade is going to contact the flats on Spyderco rods differently than it will contact the corners. When the blade begins to curve back up, the angle of the bevel changes and you have to compensate for that with angle of your hand that's holding the knife. That's easier to do if you use the corners of the SM rods. The corners are very narrow and will get in places where the flats are too wide for full contact.

When I had my 350s, I just used the corners to maintain them, but I didn't care about polishing the entire bevel. I was just looking for contact at the very edge of the bevel to keep them sharp, sort of a microbevel. It may be that your 350 is close to the SM angle that you're using, but not exact. In that case, you'd see some progress along the bevel but you'd still be doing a bit of re-beveling until the angle matches the SM all the way down to the very edge. I know from experience that the last little bit you're trying to remove with a SM can be really nasty, even with diamond rods. You may just not be down to the very edge yet. Even if that last bit is too small to see unaided, it can still be perceived when you test the edge's sharpness. That makes it seem like you're not doing anything when, in reality, you just haven't finished the job yet.

 

[RevDevil]

I agree with Dale, the corners are the trick to getting a microbevel. If you are after a complete reprofile, you might be in for a whole lot more work.

 

[HoosierQ]

Basically, with Sharpmaker I have taken to re-profiling everything so that it is 27.50 inclusive degrees. That way, I can use either the 30 or the 40 and get a microbevel of a known angle on there and maintain it. I have yet to find a factory edge that lined up exactly at either 30 or 40 and a surprising number are more than 40.

 

[SusAntigoon]

Basically, with Sharpmaker I have taken to re-profiling everything so that it is 27.50 inclusive degrees.

How do you know you're sharpening a 13.75 degree angle on each side? I do reprofiling on the EP (with the help of an angle cube) and maintain on the Sharpmaker, which makes it sort of accurate, but only with a Sharpmaker?

 

[HoosierQ]

It's really sort of an estimate. I compute the distance of the center of the spine over the stone based on the width of the blade and hold over that much. It's approximate but I know it's about that because with my method, the 30 degree sharpmaker makes a micro.

 

[Maniacal Pete]

I agree with Dale, the corners are the trick to getting a microbevel. If you are after a complete reprofile, you might be in for a whole lot more work.

I went through a series of sandpaper grits, 250 to 1200 wrapped on a dowel to create a back bevel.
It ain't especially pretty or precise, sort of dimpled, yet shiny.
Then I went back to the Sharpmaker on the corners at 40 degrees.
I could see the metal dust flying off.
After about 10 minutes - I had it sharp, but then I made a tiny, tiny chip near the belly - damn!
Went back through the stones one more time and when I was done I was able to split
a hair lengthwise; first time evah!

Now I don't want to cut anything with it!

This was a great learning experience,
these hard steels are tricky to work with.