Saber grinds - pros and cons?

Starfish · Nov 12, 2001

First a definition check: when I say "saber grind", I'm referring to something like the BM 710, i.e., a flat grind that starts somewhere around the center of the blade. I guess that the BM 940 also falls into this category.

Now the question: what does a saber grind, ala the BM 710 or 940 offer over a full flat grind ala the Spyderco Military? And vice-versa: what does a full flat grind offer over a saber grind?

Please, let's not turn this into a 710 vs. Military thread (I've already started one of those in the past

). Let's leave handle ergonomics, lock strength, etc. out of it

Matthew

Architect · Nov 12, 2001

The saber grind keeps the full thickness of the steel for the length of the blade to the point. Good for stabbing and hardier use. IMO, not as great for precision cutting. However, like with all things, each knife design is unique and will vary depending on stock thickness; depth (tallness of the blade); primary cutting edge design and angle and whether or not a swedge is included. Most factory saber grind is used in conjunction with hollow grind, not flat grind.

Full flat grind delivers precision cutting with little resistance on the way through (like kitchen knives).

You mention the BM940 as a saber grind, and it is. But what is so great about that knife is that the shallow depth of the blade (top to bottom) and the thiness of the stock make this about a good of a cutter as a flat grind.

Take a flat ground, tall blade, like the Spyderco Lum Chinese. It gives you great thin cutting ability, and the tallness of the blade stabilizes the cut as you move from top to bottom.

Joe Talmadge · Nov 12, 2001

Assuming all other things being equal (same steel and heat treat, same spine thickness, same final edge thickness), the full flat grind has less metal going up from the edge, the sabre grind has more metal, coming out at a higher angle. For the purposes of a folding knife, this means that the sabre-ground blade will be stronger, but the full flat ground blade will cut better on anything but the shallowest type of cutting, and will be easier to sharpen. I would almost always rather have a full flat grind on my folders. If more strength or toughness is needed, I'd rather the manufacturer change the steel rather than the grind -- a high-performance edge geometry is my top priority.

That said, some of my favorite folders -- like the BM 710 -- have sabre grinds. In the case of the 710, the recurved edge adds a bunch of performance back into the equation. My favorite smaller knife is the calypso jr., which I like specifically for the outrageous performance that results from the full flat grind.

When it comes to bigger knives, like big choppers, sabre grinds don't just make the blade stronger, but the wider angles wedge the wood apart, and make knife less likely to stick.

Starfish · Nov 12, 2001

Joe spake thus:
Assuming all other things being equal (same steel and heat treat, same spine thickness, same final edge thickness), the full flat grind has less metal going up from the edge, the sabre grind has more metal, coming out at a higher angle.

(Forgive me if what follows is confusing - I am trying to state something in terms which I am not completely comfortable with

)

If I understand this correctly, a sabre grind has a wider final bevel than a flat grind. By final I mean furthest from the edge. Is that right?

Joe also spake:
For the purposes of a folding knife, this means that the sabre-ground blade will be stronger, but the full flat ground blade will cut better on anything but the shallowest type of cutting, and will be easier to sharpen.

I understand, based on what you said above, why a sabre-ground blade would be stronger. But is the blade considerably stronger than a full flat grind would be? And why is a sabre-grind harder to sharpen than a full flat grind?

Thanks for the responses!

Joe Talmadge · Nov 12, 2001

starfish -
The sabre grind can be a bunch stronger. As you go up from the very edge, the difference in angle (and amount of metal) can be considerable. And, of course, the more metal and strength the sabre grind has, the worse it will fare performance-wise versus the full flat grind in deeper cutting.

For the same reason, sharpening the sabre grind means you'll have to take off more metal as you sharpen up.

Joe

Starfish · Nov 12, 2001

Thanks for clearing that up!

Matthew

Burke · Nov 12, 2001

When it comes to bigger knives, like big choppers, sabre grinds don't just make the blade stronger, but the wider angles wedge the wood apart, and make knife less likely to stick

They also leave more mass, which can be useful for a chopper. I like full convex grinds, but that's a whole 'nother can of worms.

Cliff Stamp · Nov 13, 2001

Joe :

When it comes to bigger knives, like big choppers, sabre grinds don't just make the blade stronger, but the wider angles wedge the wood apart, and make knife less likely to stick.

This is always a losing proposition. If you have to force the wood further apart you have to exert more force on the blade, which means basically under a given load you will see far less penetration. Doing a partial height flat grind with vertical flats is a horrible configuration for chopping. Yes it will bind less than a full height flat grind, however this is mainly because it will suffer horribly in regards to penetration (decreased depth of cut, decreased about of wood to bind onto the blade).

There are far more effective ways to decrease binding as it is a more complex issue than just cross section. For example the worst blades in regards to binding are sabre-flat grinds - machetes. The wood will bind very strongly around the flats. The optimal profile for chopping, which achieves strong penetration with a minimum of binding is the triple convex - hollow - convex grind found on axes and khukuris. The convex grinds will minimize binding onto basically one point on their curvature and the hollow relief prevents binding along the main blade body.

In regards to mass, yes a sabre grind will be heavier, but again there are more effective ways to increase this apsect. Balance is key and a simple taper of a tang can shift the balance far forward and can get the necessary heft without having to give up all the cutting ability that a partial height grind produces. As well the blade can simply be made wider, a little longer etc. .

Sabre grinds are stronger than full height grinds, significantly so, but they are not more efficient materials wise. You can get the same level of strength with a greater level of cutting ability in a slightly thicker stock with a full height grind. For the vast majority of the time they are done simply because it is cheaper to do so. As well like Joe mentioned they give up cutting ability, and the only way to get the shallow cutting ability to be similar to a full height ground blade is to grind the edge on the sabre grind blade at a more acute angle, which will obviously weak it. So basically you are stuck with a poor cutting blade, or one with a weakened edge.

-Cliff