Cutting edge angle

[Bill Thomas]

I just sent my first batch of knives to Peters Heat Treat. I left the cutting edges approximately .025. I don't know how to finish the cutting edge when I get them back from HT. For discussion lets say my original flat grind angle is 3.5 degrees on each side. I have read that the finished cutting edge should be around 20 degrees on each side.

With that said here are my questions.
Do I start my finish grind at the original 3.5 degrees or do I jump into the 20 degree range to finish the edge? If the answer is continue with 3.5, at what thickness do I start the 20 degree grind? I assume it boils down to this; do I want a wider 20 degree bevel on each side or a very thin 20 degree bevel (that's a question). What is best, wide or thin?
As I said I'm new at this so any advise is welcome and appreciated.

 

[Don Hanson III]

I want my blades almost sharp before I sharpen them.

I'd grind the blades to a edge thickness of around .010" after heat treating...

 

[Cody Hofsommer]

What is the steel and what is the job of the knife? A fillet knife and a chopper are goin to have different thickness and angle.

 

[Bill Thomas]

Thanks Dan
Cody, it's 52100 1/8 x1.5 skinners
Thanks

 

[Bill Thomas]

Sorry I meant; thanks Don.

 

[Hengelo_77]

clean them up after ht with the same gritt size as you finished with or one lower.
Then set the edge at 20degree per side measured from the flat (ricasso or above the bevel)
The smallest angle from a 1:3 triangle wit one 90degree angle is 20degrees.
1:4 is 15degrees wich can be used for a finer blade

 

[Cody Hofsommer]

.010 with 15 degree, each side (30 inclusive) should cut like a laser, and be tough enough for the intendid task.

 

[Bill Thomas]

clean them up after ht with the same gritt size as you finished with or one lower.
Then set the edge at 20degree per side measured from the flat (ricasso or above the bevel)
The smallest angle from a 1:3 triangle wit one 90degree angle is 20degrees.
1:4 is 15degrees wich can be used for a finer blade

I don't understand. Can you dumb down the 1:3 / 1:4 relationships?
Thanks.

 

[Bill Thomas]

.010 with 15 degree, each side (30 inclusive) should cut like a laser, and be tough enough for the intendid task.

Thanks Cody sounds like a razor. I can't wait to get them back.

 

[Omega Leather Works]

I've experimented a lot with edge angles over the last few years in various steels. There's never been a time when I needed 40° inclusive.

I don't have much experience with choppers or axes, but I wouldn't start with anything much more obtuse than 40° anyway, even in those circumstances. YMMV.

A microbevel is always an option too for an acute edge that displays signs of rolling. Your edge should be tougher, yet still has the geometry that an acute edge offers.

I do my mb's between 5-10° over the bevel angle. (30 with a 40mb)

I'm sure you already know (you're a knifemaker) but to clarify on the off chance that someone reading this doesn't...

The primary is the flats (on a ffg) that starts at the spine and continues down to the secondary, which is the bevel that we sharpen. A microbevel is the very short bevel that you apply to the secondary. That forms a very small shoulder and continues to the apex.

Usually micros, at least mine, are made with a couple of light edge leading strokes on the stone, or by lifting the angle of the guided rod on a guided sharpener.

 

[Cody Hofsommer]

I don't understand. Can you dumb down the 1:3 / 1:4 relationships?
Thanks.

I think what he is saying is a right triangle with one leg 1" and one leg 3" you will have 20 degrees at one corner. If that leg is 4" it would be 15degrees. I havent heard of this, but it's kinda cool of it works out. Correct me if I'm wrong

 

[Hengelo_77]

Yes, Cody that is how I mean it

Make sure that the angle between blue and yellow is straight (90degree)
Then if yellow is 3x longer then blue the angle between red and yellow is 20degrees
(say blue is 1" and yellow is 3")
4x makes 15degrees
I have two blocks of material in these angles in my sharpening box to help me keep the angle.
I put them on the flat of a blade, set the sharpener at that angle, make a dozen passes and reset the angle.
It helps to get a steady hand and keep your angle

 

[Omega Leather Works]

Oh hey, Hengelo, that's pretty cool. Now I understand it better.

 

[Karl B. Andersen]

I want my blades almost sharp before I sharpen them.

I'd grind the blades to a edge thickness of around .010" after heat treating...

I once heard you could only take Don't knives out of their sheath in a dark room because the shadow of his blade would cut the leg off a table.

 

[Don Hanson III]

I once heard you could only take Don's knives out of their sheath in a dark room because the shadow of his blade would cut the leg off a table.

That's right, bubba!!!