Relief (bevel) question for sharpening geeks

T

thombrogan

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Nov 16, 2002
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How many of the veteran sharpening geeks and sharpeners in training here drop the shoulders of their knives as low as possible before applying a microbevel as their main edge?

Also, is doing so with a stainless knife a good idea or is it better to just get a good, polished edge bevel that is fairly thick lest the bladechipping fairy pay your knife a visit?

Many thanks in advance,
 
Hm, i´m not a veteran. But for me, it depends on what i want to cut with the knife.

I got two razor blades wich are as thin as possible, by relief and edge. But i only cut my barb with them, nothing else!

I got a BM 812s, wich i found is quite small, not to consider it to "hard use", so i grinded the bevel in the way i take the knife for fine cutings (something between 10 or 15° not included).

My 806D2 came with a bevel around 15+°. I gave it to a prof to get it up to 20°. Just because i want the material over the edge (he is grinding by hand, so the edge is somehow convex), if i got a knife with a strong (thick) blade. It will never shave any hair, but it cuts from newspaper up to hard wood (and maybe will open cans for me) and holds its edge for long. If i would take a smaller angle, i guess reprofiling would be the most time i spent on the knife.

As long as nobody can definatly tell how strong steel grades are, i use to think, to have a stronger than average steel (D2) and follow those old fashioned instructions on edge bevelling. (On that day, when someone can proof me, that D2 has the double strength than AISI 420, i might set the bevel back)

So, my question back to you is: What do you want to cut with the knife and how shure is it, that you lead the knife without twisting?

This would determine, how thin a bevel could be.

JMHO.
 
You can do it with very brittle steels as well, I have a D2 blade at 62 HRC, which is relatively very brittle and the relief grind is the primary grind because I completely removed the shoulder. But yes in general, you have to leave thicker edges on less durable steels, so in effect those steels don't cut as well as they induce a greater constraint on the limit of the edge geometry.

Pushing as far as you can go besides increasing cutting ability, also greatly enhances speed of sharpening. I have recently been doing a lot of carpet cutting and as a side effect a lot of significant sharpening. Having knives with high relief grinds makes the process go even faster. It is not as nice as having a optimal primary grind, but outside of true custom knives (or a lot of time on a belt sander), that isn't really an option.

-Cliff
 
I want to use the knife for woodcarving, opening sacks of kitty litter and potting soil (two separate bags), cutting strings, cutting cardboard boxes to make forts for the pet rat, opening boxes, snake patrol, cutting branches and thorn bushes, cutting plastic such as soda bottles, and minor food prep.
 
The D2 blade I have has done all that, with the note that it has not been used to cut the very thick plastic around the bottom of the bottle, but can cut through the sides easily. The only concern in the above would be staples in the cardboard. Some of the heavy industry ones would badly gouge the blade due to the very acute edge bevel, for thick metals like that you can damage metal up to 0.005"-0.010 thick, which isn't significant for most knives, but on acute ones that can be up to 0.030" deep, which is far beyond the extent of the edge bevel and way up into the relief.

To clarify, I assume you don't mean chopping branches but just cutting them. If you are chopping them, and the knife is decently heavy you will need to thicken the edge. However it takes a pretty hefty knife to start to approach a 0.020" thick edge (10" bowie class), and the edge is then just 10/15 with a double grind. Small knives can still take heavy whacking with very thin bevels. The Pronghorn for example has an edge just 0.005"-0.0010" thick and has been used for extensive heavy chopping (snap chops with a two fingered grip from the shoulder) including into knots. No problems.

-Cliff
 
Yes, cutting, not chopping. The closest I would do that resembles chopping is push-cutting. I do have a D2 folder (806D2 from Benchmade), but I have some folders in 154CM and AUS-8 that I want to get the most slicing use out of them that they have.

Thanks, Blop and Cliff!
 
Why not a triple grind. What in fact you end up with is a staged convex gring. First, grind the flat, Second, grind away the shoulder then apply a relief. Works well with butchers and kitchen knives. Done properly you will not grind away a blade to nothing as some meatworkers do. They are obsessed with shoulders and wonder why their boners end up as toothpicks.
 
On most of my knives I put a 25* incl bevel on them at 1200 grit, then mouse pad them with 2000 grit, then strop. In the field they get touched up with diamond and ceramic steels, and/or strop, and then back on the mouse pad and strop at home. Effectively ends up being a convex edge, and lasts a long time. It works better than anything I've done in the past. I'm going to try some at 20* back bevel next time they need profiling.
 
JDEEBLADE,

Thanks for the advice. I don't want to sharpen my knives away to nothing so a triple bevel might be a great solution.

Stich,

I just used the EdgePro to put a 10 degree bevel on my Benchmade 730 Ares and then mousepadded it into an acute convex edge. Convexed it before, but it was too thick. It would shave hair, but the edge was too thick to cut branches. Last night, it got pushed into 45 micron, 5 micron, .5 micron, and .3 micron lapping films until a burr was formed and gently abraded off at a higher angle. Not sure how it will cut, but I can't wait to see how pretty it'll look after retouching the edge on the smaller grit papers over the next few months.
 
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