Questions about double-beveling

Starfish

Starfish

Joined
Jun 14, 2001
Messages
1,256
There have been several threads recently where Cliff Stamp pointed out one virtue of double beveling - namely, speed of setting a secondary bevel at a slightly more obtuse angle than the primary bevel.

This observation is borne out by my own experience as well, most notably in the reprofiling of a mini-AFCK with M2 steel to a 30 degree included primary bevel and 40 degree included secondary bevel (can anybody guess which sharpener I was using? :rolleyes: )

Questions:

1) Are there any other benefits to double-beveling besides ease of sharpening? Any disadvantages?

I'm thinking of thinning out the primary bevel even more on my Mini-AFCK and setting the secondary bevel at 15 degrees per side. However, as I am using the Sharpmaker (whoops, gave it away!), this means that I must either freehand the primary bevel or adjust the base of the Sharpmaker somewhat. Which leads me to my next question:

2) Is there a general rule of thumb for the angles used when double beveling? Something like, "if the secondary bevel is at x degrees per side, then the primary bevel should be at most y degrees per side."

Thanks for your help,

Matthew
 
1. Advantage: Less steel behind the edge to hinder your cutting performance.

Disadvantage: can make knife look less pretty. You can smooth out and polish your back bevel by going over it with finer grit abrasives than the one you originally used to grind the back bevel.

2. No. Unless you have the neuromuscular control of a surgeon or or own a sharpening system with more than two preset angles (EdgePro, Lansky, Gatco), it's touch-and-go. If you win the raffle on the Razor Edge Book of Sharpening, you'll see knifes ground in ways that make me nauseous to make the finished edge cut better.
 
thombrogan spake:
If you win the raffle on the Razor Edge Book of Sharpening, you'll see knifes ground in ways that make me nauseous to make the finished edge cut better.
Click to expand...

Well, I wasn't planning on doing anything THAT extreme (I have the book too!)...but I would like to see how far I could take it before I have to sacrifice the finish of the blade itself :)
 
...could you try using the super-secret official Bladeforum method of applying a convex/Moran ede to your blade using wet/dry sandpaper glued to mousepads?

I was going to use a RazorEdge guide to put three or four bevels in my 140HS and then try that method, but, since I'm a total novice with a clogged up course stone, I'm going to try just using the mousepad and sandpaper within the next few weeks (don't really need to as I only seem to use folders, but I want to see how it looks and cuts).

Does anyone who invented the 4M (Minnesota Mining, Mineral, and Mousepad :p ) method? I like crediting the proper sources. I currently call it the Buzzbait/Stamp method.
 
I have an Edgepro, and have been playing around with this. I took a small carbon steel pocket knife, and set the primary angle/relief at 20 deg total and the secondary at 30 deg total. This thing cuts like a laser. Only problem is that it is VERY susceptible to edge damage, especially when whittling. You might want to go slightly thicker.

A couple of observations:

Razor edge book recommends re-grinding the primary bevel to a burr every time you sharpen the knife. This seems like it's wastefully removing too much steel. With a quality knife, I've been steeling 4 - 6 times when it's dulling, then when that no longer works, just sharpening the secondary bevel. I can get away with just sharpening the secondary bevel several times before I need to thin out the relief. Like Cliff says, grinding the secondary bevel takes about 10 strokes on a stone.

Once you get the primary bevel done, it's quite easy to sharpen the knife by hand from then on. It really works well.

As for ugly, my primary bevel is about 1/8 to 1/4 inch wide, so it doesn't look so nice, but man, does it cut. Even when it's dull, it out-cuts a lot of thicker grinds.

Have fun!
 
swede79,

Stupid question: how do you tell when it is time to thin out the relief? Do you just go by how long it is taking to grind out the secondary bevel?

Thanks,

Matthew
 
Another question swede - silly or otherwise:

What advantage(s) did you see in purchasing the EdgePro as opposed to the Apex?
 
Starfish,

Yes, usually it takes about 10 strokes on a fine ceramic or fine Norton India stone to get the secondary bevel. When it gets a lot longer, OR, when I have to greatly increase the sharpening angle to only use 10 strokes, then it's time to thin it out.

When I'm not sure if I'm doing things right, I'll use my Edgepro as a check. My secondary bevel, if I make the angle 3 - 5 degrees more obtuse, is only a mm or two wide. That's why it's so fast. Also, in case my last post wasn't clear, I steel several times between EACH sharpening - the beauty of steeling...

Switched, Thombrogan is right, I have an Edgepro Apex. I find it to be just fantastic, although I'm really starting to enjoy freehand also. There's no way, however, that I could get the inital primary grind (relief) by hand, I'm just not that consistent. I don't feel too bad about it, since most makers use a belt sander.... :D

I used to want an Edgepro Professional after watching the video, but honestly, the Apex is just fine for my needs.

These are great questions, keep them coming. The devil is in the details.

Keep in mind that I'm not a good sharpener, it's taken me a long time and a lot of experimentation to get here, and I still have a long way to go. I watch my father in law, who is a machinist, "break" all the "rules". He holds the stone (little 4 inch deal) in his left hand up at chest level, the knife in his right, and in about half a minute, gets a hair popping edge that scares me. There's no substitute for experience....
 
Thanks for that swede. After a fair bit of reading over, it seemed to me the Apex was the go. Notwithstanding a considerable amount of support and the diamond rod option, the Sharpmarker seemed a bit limiting in certain respects and wasn't that much cheaper on the diamond rod basis in any event.

No Thom swede didn't indicate precisely which one he had. But if someone says "EdgePro", that is suggestive of the full version, to me. If I had the other I would say "EdgePro Apex", or get "Apex" in there in some way, at least. Unless you'll tell me people would say "EdgePro Pro" for the alternative? Maybe they should, but I haven't seen it done to date.

Edited to add:

It's late here, so... All I mean is, no swede didn't say which etc. But that was the point of my question, in order to assist my own choice in this respect. Which swede kindly did. No biggie.
 
Switched, you're right, I left it open for interpretation. I'm a lazy typist.... ;)

I wonder if I just type Apex, would people know what I mean?

At any rate, I HIGHLY recommend the Apex, it's great!!! :)
 
That'll do me, regardless.

You strike me as knowing your stuff. No doubt your FIL is a wiz but I don't have any delusions concerning myself in that regard, that's for sure.
 
I like a pretty coarse edge, but no matter what finish edge you like do this. I polish the back bevel. Also I will round off the small shoulder.
 
Honestly this can start to feel like some secret society.

What's next? Colonel Mustard in the library with the candlestick?
 
db,

sounds like you might want to switch all the way to a convex edge. Buzzbait posted some outstanding instructions on how to do that. That's my next project, to get proficient at that.

Mr. Green, wrench, the study... :eek: :D
 
Yes well I think I'll adjourn before it gets to the Cliff Stamp on the bannisters with the crowbar stage, at this rate.
 
It was Switched, with the keyboard, in Australia!

Did I guess it correctly?

Switched,

I hope that my rude and brusque reply hadn't implied that I knew which model of EdgePro, Apex or Professional, was being used. My initial assumption will always be the Apex as it costs less.

Speaking of costing less, if you're handy with glue or tape, you could adhere course sandpaper to the medium rods on the Sharpmaker and replicate the diamond rods at a fraction of the cost.
 
Starfish :

Are there any other benefits to double-bevelling besides ease of sharpening?
Click to expand...

As Joe noted it eliminates burrs really quickly. It can also make a dramatic difference in edge durability.

Any disadvantages?
Click to expand...

There is a slight loss in cutting ability due to the more obtuse bevel, but since the bevel is very narrow this isn't significant.

Is there a general rule of thumb for the angles used when double bevelling?
Click to expand...

In regards to ease of sharpening and burr removal you don't need to go beyond 1-2+ degrees. If you want a large increase in durability then set the angle accordingly. As noted since the bevel is very narrow you don't lost much in cutting ability so don't hesitate to go even fairly obtuse like 22 degrees or so.

swede79 :

Razor edge book recommends re-grinding the primary bevel to a burr every time you sharpen the knife.
Click to expand...

That is not necessary and removes the primary advantage of double bevelling and as you note is very wasteful besides.

As for ugly, my primary bevel is about 1/8 to 1/4 inch wide, so it doesn't look so nice, but man, does it cut.
Click to expand...

Yes, if looks are a concern you could always carry a really nice looking knife to admire and another that actually cuts.

Starfish :

[when it is time to thin out the relief]

Do you just go by how long it is taking to grind out the secondary bevel?
Click to expand...

Yes, and also if you notice any decrease in cutting ability.

thombrogan :

[sandpaper + mousepad]

I like crediting the proper sources.
Click to expand...

Claiming to invent this is only slightly less extreme than claiming to have invented abrasive sharpening in general. As long as there has been sandpaper people have used it to sharpen knives. Sandpaper is after all the same abrasive that is in a hone. It is very popular in wood working groups, do a net search for "scary sharpening" or "scary sharp".

In regards to convex bevels, Mel Sorg told me about using sandpaper on a soft backing to put a full convex bevel on a knife, from spine to edge. This was on Knifeforums back before Bladeforums existed. He learned it from his father who worked cutting paper and doubtless learned it from the people he went to work with. You can do it on both a hard and soft surface with a slight change in technique. You roll the blade on the hard surface to create the curvature. On a soft surface it is created naturally as the surface indents.

A year or more later I worked with a native knife maker from Malaysia who showed me the traditional way of sharpening full convex bevels on large parangs with a flat hone by working a small hone edge trailing, very similar in essence to the technique that Mel Sorg described on the hard surface. They used two grades of hones and just broke up a large 8x2 into a bunch of small pieces. He also later made a knife from Al and sharpened it with sandpaper, steel wool and Brasso.

Buzzbait I think popularised the idea of a mousepad, and could have been the first person to mention it on the forums.

Joe popularised most of the current forum info on sharpening and was the first person to promote several very valuable tips such as leaning other hones on the Sharpmaker, double bevelling, multi-bevelling (sharpening different sections of the blades in different grits), etc. .

-Cliff
 
Originally posted by Cliff Stamp
[sandpaper + mousepad]

Claiming to invent this is only slightly less extreme than claiming to have invented abrasive sharpening in general. As long as there has been sandpaper people have used it to sharpen knives. Sandpaper is after all the same abrasive that is in a hone. It is very popular in wood working groups, do a net search for "scary sharpening" or "scary sharp".

-Cliff
Click to expand...

Thank you very much! So it looks like edge-trail sharpening, ala Buzzbait, is popular in North America and the Indochinese penninsula. So the inventors may have been Dutch, French, or Portuguese explorers seeking riches and dispensing convex-edge sharpening tips across the world. Or, after inventing the internet and the mousepad, it was former USA VP Al Gore's invention.

:rolleyes: Just kidding! No flames, please!
 
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