Custom "Buyer" Pet Peeves

RJ, I agree in theory with all that you said in the above, however in practice I have been getting very good edges in terms of sharpness and edge retention by working in what I feel is the worst way possible. Using worn 100 grit cheap AO belts, I press hard, and don't buff the edge. After grinding I just strop on canvas loaded with paste to remove debris.

This method has given very strong results on rope cutting, for Carbon V, 440A (SOG), A2 (Mission), and whatver Camillus is using in the Becker line. I have not tested it yet on the CPM's but have just recently reworked a custom D2 blade (62 RC, cryo), that will see some cutting soon. I do have a CPM-3V blade that I intend to sharpen in this manner soon.

Of course the very aggressive edge thus formed would be very lousy on high impact work like chopping as it would get mauled very readily, but on slicing work it is the best I have seen so far for ropes and similar materials. I have not tried new belts yet though, so they may give even better results. You also run a a much higher polish, and getting a sharp edge gets much harder as you increase the polish.

A few questions :

What is sharp to you? Shaving is a very vague term, can your blades for example cut hairs above the skin going either forwards or backwards through the direction of growth?

Do you feel that new belts are also needed on the fairly plain steels like 1095, which are far more easy to cut than the high alloy CPM's?

Do you get better results on a particular type of belt, abrasive type or whatever ?

-Cliff
 
Cliff: For the steels you mentioned, I am not surprised that your technique works well. I can sharpen A2 in ways that have virtually no effect on the CPM alloys. My edge is not particularly polished either-polished edges do great on paper and shaving but do poorly for "real" cutting like flesh and rope. Having the microteeth can yield an edge that will do both.

WRT your questions on shaving-I have found it to be a very arbitrary comparison. When I am happy with an edge, it will pop individual hairs at the skin surface, cutting from any direction.
Honestly, at this point I can assess the edge best by how it feels against my thumb-when it feels "right", I know how it will perform in most of my tests without actually performing the test. That just comes from doing it hundreds of times.
I would worry about the durability of an edge that would cut hairs above the skin level, but, it may depend on the nature of the hairs, too.

WRT what belts to use, I like the 3M ceramic belts in 220 grit. A while back, I had posted that I wasn't happy with how sharp the CPM alloys got when I sharpened them. The new belt technique heas kicked up the sharpness to where it equals or surpasses any of the other steels (A2, D2) sharpened by my "old" methods.

Stay Sharp,

RJ Martin
 
Howdy RJ-
I guess it's no surprise to you that when people talk about "sharp" knives, your name pops up. I'm not brown-nosiong, it's a simple statement of fact. The extra effort shows.
 
I would worry about repeatability and heat using worn belts. The edge of the blade has a good heat sink in the rest of the blade, It cools quickly when removed from the contact with the belt. However, you are depending on the strength, hardness and wear resistance of the surface and the micro teeth on the edge and That is where the heat is being created. The heat treat of the edge needs to be retained. This is a major concern of mine.

My 2cents,
Dan Farr
 
I agree in theory with the concern about heat, but in practice I have never seen any effect on belt sharpening. This weekend I reprofiled a custom D2 blade (Mel Sorg), at 62 RC. When sharpening, my belt was getting worn (100 cheap AO) so I was pressing hard and doing multiple passes before cooling. Running the blade until it got that hot that I had to release contact. I was doing this on purpose as a worst case senario.

The edge formed was clean and sharp. With no buffing except canvas for debris removal, the blade started slicing 3/8" hemp needing only 7.5-8.5 lbs over a 2" draw. After 1022 cuts the force had only been raised to 12-14 lbs. It had dulled, but was still easily cutting the rope with no fraying. The blade could also easily slice fine newsprint vertically, with the paper floppy, not held rigid.

Checking the edge under magnification, much aggression remained in the form of large teeth at 0.2-0.3 (/20) mm, and micro teeth in between about ten times smaller. The microteeth had worn from the inital state and there were regions of flats present, but the blade obviously still had lots of life left in it.

I am curious to see how much rope it will cut before the force exceeds 20 lbs, and may try another thousand to see where that takes me. In any case, even then, it will still be twice as good as most factory blades in raw cutting ability as even the better ones come it at 30-40 lbs.

The edge is 0.030" thick behind the back of the bevel, which is ground at ~5.5 degrees per side. Essentially the blade was held flat to the belt.

Other steels may give different results, I will be curious as to how the CPM's will respond.

-Cliff
 
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