Bad heat-treat on a BM?

J

Jeff O

Joined
Feb 29, 2000
Messages
507
I have two knives with ATS-34 blades. One is a Benchmade 720 and the other is a buck odyssey II. There is no contest between the BM and the Buck, in terms of edge holding ability. The odyssey stays sharp much longer and is easy to sharpen. The BM however, is very difficult to sharpen and does not seem to get as sharp as the Buck. I changed the angle of the edge bevel, which helped some but not much. Was my knife improperly heat-treated? Or is the heat-treat on my Buck just that much better? (If I am not mistaken, Paul Bos overseas the heat-treat process.)

Has anyone else had the same problem with their Benchmade?
 
It is probably not the heat treat that makes your axis perform poorly. My old ats odessey used to feel much sharper than my axis. It was because the axis was saber ground and the edge was thick like a chunk, while the odyssey was deeply hollow ground to a thin edge. Buck also puts a 15 degree grind on all their new knives making them feel very sharp out of the box. The Axis will be harder to sharpen because it has more metal behind the edge that needs removal. Don't do what I'm about to suggest. You could always test the heat treat if you were really worried by pressing the two knife edges together near the base of the blade. But don't do it if you want to keep your blades nice. My odyssey is no longer nice
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[This message has been edited by generallobster (edited 10-25-2000).]
 
A very long time ago, BM had some trouble with heat treat. They discovered this, Les de Asis told me, by the fact that the thumb studs, which were pressed into a hole, would crack through the hole. They modified the heat treat so that the steel was softer and tougher.

This was a LONG time, and many knives ago. I know of no current or recurrent problems with BM heat treating, but cutting to the chase, the only way you will know for sure is to send it back to BM and have them check it for you.

Walt
 
In my personal experience, I have seen problems with BM that indicate a poor and inconsistent heat-treat. I have never had an ATS-34 BM I could sharpen worth a damn (only had two or three). I have two of their butterfly knives as well (model 45 & 69), one sharpens up easily, and to a hair-popping edge, the other one is very difficult to sharpen.
 
A more obtuse edge angle requires less metal to be removed during sharpening because it is not as wide and as well will sustain less damage during use so less metal will need to be removed in the first place.

One of the main reasons that people cite difficulty in sharpening obtuse bevels is that they are using an angle significantly different from the NIB one and are not in fact actually grinding on the edge at all.

It should be possible to make the edge of your Benchmade sharp, however since the primary and edge grinds are both much thicker than on the Buck, it will not cut nearly as well.

Note as well that since the cutting performance of the Buck is much higher, it can get much blunter than the Benchmade and still out cut it, giving the impression that it has a greatly enhanced edge life.

As for Benchmade and heat treats, I have seen brittle blade failures under low stress on blades purchased in the last couple of years.

-Cliff
 
Thanks for the input. I understand that the Buck will appear sharper because of the blade grind and the angle of the edge. I spent what seemed like an eternity on the sharpmaker with the BM and created an angle that is only slightly more obtuse than the Buck. I can get the BM to cut hair off my arm but not effortlessly like the Buck will.

Here is the scenario when I noticed the difference in performance. I work in a sporting goods store and I used my 720 to cut open an order of Levi's that consisted of 10-15 boxes. When I was through, I wiped down the blade with some oil to clean it and then I inspected the edge. I could see light reflecting off of spots on the edge and there was no chance of cutting cleanly through a piece of paper, let alone shaving hair off my arm. I used my Odyssey to open the next order of Levi's that came in, which consisted of 15-20 boxes, and some other chores throughout the day. Needless to say, the Odyssey cut better because of the blade design. At the end of the day, I cleaned the blade and inspected the edge. It looked as it did at the beginning of the day and it could still pop hairs off my arm. I have had similar results with these two knives on separate occasions as well. That rules out the possibility that one set of boxes was meaner and tougher than the others.

It took five minutes or so on the sharpmaker to restore the edge of the BM whereas it took a couple of licks on a strop to bring the Buck back to shaving sharpness.
 
I've sharpened many a BM. All the same, no difference in ease or difficulty to sharpen them. I grind with a coarse stone at a 15-degree angle, then finish with the finer stones and strop. Always shaves.

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Chang the Asian Janitorial Apparatus
 
Jeff, thanks for the clarification. One thing you might want to check is to steel the Benchmade after it blunts. If it is significantly restored it might be a bit too soft. Or if you can take a look at it under magnification to see if the edge has broken away in the spots that reflect light. It might then be a little too hard.

The curious thing however is that you can't get it to shave well. This would make my first guess be that you are simply not sharpening it well to begin with. However if you have good success with other blades including when you had to change the NIB angle, I can't really see why you would have a problem with the Benchmade unless the blade geometry is odd (curvature or something).

The only thing that comes to mind is that there may be a difference in how the Buck and the Benchmade steels develop an edge burr. If you are leaving some of the burred steel on the edge of the benchmade this would explain the quick edge loss as well as the denting/fracturing that is causing the light spots.

-Cliff
 
If you have a few spare $$ laying around, try contacting Phil Wilson. If you include $5 for shipping/insurance he'll test the RC value for you. E-mail me for more details! My AFCK was tested by him. A nice 59 it came to!

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"Come What May..."
 
weird

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Take both knives to a third party (a local maker or shop) and have them professionally
sharpen the knives for you. Then test the knives to see how they perform. The knives have different blade grinds and need to be sharpened respectively for optimal performance.
 
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