Factory edge, Cutting edge and sharpening

S

Soupladel

Joined
May 14, 2020
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17
Can someone explain, or point me in the direction of a resource that explains the thinking behind using a wider angle to sharpen a knife that has a narrower factory edge.

For example, I had read elsewhere that it was recommended when using the Spyderco Sharpmaker to sharpen a Leatherman blade, to sharpen at 40 instead of 30 degrees despite the fact that leatherman has a factory edge of 32 degrees total.

Equally i was given advice in these forums to sharpen my Endura 4 at 40 degrees also despite the fact it comes with a 30 degree factory edge.

I am sure there is a good and logical explanation for it beyond peoples preference for an angle to sharpen at. I can't help but think that sharpening at a wider angle than the factory edge will result in eventually rounding of the apex of the blade?
 
The sharpmaker is a honing rod, and is designed to work at an angle larger than the angle of the primary bevel. What is does is make a 40 degree (20dps) microbevel.

You can certainly sharpen a knife at a lower angle than the existing, factory angle BUT that will likely require removing a fair amount of steel to make a new bevel, more than is practical with the sharpmaker.
 
Thanks for that.

I realise that what you are talking about is effective re-profiling when looking to sharpen at a narrow angle than existing, but speaking in general is it better to sharpen at the same angle as existing or, like you say is creating that microlevel the way to go?

I realise its probably difficult to match the existing angle exactly (using a system such as the sharp maker) because its been done on a grinding wheel in the factory and probably isn't exact, but my worry is that a micro bevel will lead to worse retention or am i overthinking it?
 
The microbevel "doesn't care" what's going on further up the blade, as long as you are hitting the apex on both sides. Now if the factory edge was 10 degrees on one side and 25 on the other, like the Spyderco Manbug V-TOKU2/SUS410 I recently bought, then you will have to regrind the bevel entirely.
 
You could, over the course of time, use the narrower setting (30°) on the SM to gradually narrow the back-bevel behind the edge on knives with an edge angle wider than the 30° setting on the SM, while at the same time using the wider setting (40°) to do periodic touching up of the edge itself. In time, once the narrower back-bevel is set and getting closer to intersecting the apex of the edge, you could then start using the 30° setting to do the sharpening of the edge. How long all this will take, to get to that point, will depend on how often you do it and whether or not you take advantage of the coarser rods (diamond or cbn) for the Sharpmaker.

OR, at some point when you become more comfortable with freehanding on stones, or if you invest in a more versatile system for reprofiling, you could thin out the edge that way. In the long run, narrowing the edge angle to 30° or less (inclusive) will have the edge cutting much better than it will at something wider. Virtually any EDC blade used for normal, non-abusive tasks will hold up just fine at 30° or less. So there's good incentive for doing it, one way or another.
 
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i had considered getting the Lansky, but i have now had my head turned by the KME system which i will hope to get sometime in the future
 
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