Full Convex or Flat Primary Grind with Convex Edge Bevel?

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switched

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Feb 7, 2003
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By way of background:

This is in connection with a Dozier Professional Guides Knife. So that is a blade length of 4 3/4 inches. In S30V. To be used as a fisher, hunter and camper. First and foremost, my concern would be my idea of what a knife is really for - cutting, slicing etc. There is a tad of that elusive and illusory attempt to 'have it all' here though, such that if there were some 'in an absolute pinch' chopping ability then great. BUT, not if that is going to GREATLY reduce performance in the former respect. All a question of degree and balance, in other words.

Just to complicate things a bit more, I'm wavering just a little, thinking about the Straight Hunter. Mainly because I don't have large hands and some comments have started me thinking the PGK might be more that line. My hands are on the smallish side I'd say, near enough to identical to those of Jack Nicklaus in 'Golf My Way' I've noted, whatever that might mean. Anyway that might be more of a grip concern, which I can leave for now.

I've gone through Joe Talmadge's FAQ (doesn't really go into this level of detail) and other resources, like this one -

http://www.mhcable.com/~yocraft/sosak/convex.htm

I'm not resolved on which would be preferable, given my usage. Full Convex or Flat with Convex edge. Considerations which have occurred to me include:

- strength. Greater with full convex I'd think.

- weight. Again, greater with full convex.

- cutting.

- sharpening. In particular, I'd like to be able to restore/maintain the edge without scratching the hell out of the blade.


Any comment on the relative merits of these two?
 
I'm a recient convert to the convex grind having reciently in the last few weeks put a convex edge on one of my knives.

As for the pros & cons between full and edge convex sharpening I would say :

Strength - Convex edge, it will leave a thicker amount of steel behind the cutting edge.
Cuttting power - Full convex, to get a full convex you will have to thin down the steel imediately behind the cutting edge which will greatly reduce the friction of the blade passing through the to be cut medium.
 
Hi Switched,

To avoid scratches on the blade from sharpening, use several transition steps between your coarsest and finest abrasive. That's assuming that the edge isn't initially convex ground. Otherwise, use the strop and finest abrasive you can find.
 
I've owned 2 of Dozier's Pro Guide Knives which I've stupidly traded or sold away.
I have medium hands Bob's handles are probably the most comfy I've held yet.
Never understood why Dozier's site says they are for "big hands".
As for grind, I think Bob only offers Convex or Hollow Grinds on his blades, not flat grinds. If you really only want to cut, get the Hollow grind. An absolute killer combo with his awesome D2. The Convex grind will take more abuse, but his PGK isn't big or heavy enough to even do minor chopping. Plus the sharpening aspect of convex grinds may make it a hassle to get razor sharp again.
Lenny
 
That's a tough question. A full convex grind will add some weight to the blade end of the knife, which will in theory, add chopping ability. I personally don't think it matters on this size knife though. Both the Straight Hunter and PGK are probably too small and light for chopping. You're much more likely to be batoning such a knife to split wood. Fortunately, you also want a full convex grind for maximum splitting power with a baton, so you don't have to choose. Both aspects of wood preparation are better covered by a full convex grind.

The downside I see to the convex grind, in comparison to a flat grind with a convex edge bevel, is weight. The flat would probably be lighter. I'm not positive about this, but it's my gut instinct.

As far as finish of the blade goes, I think you’ll actually prefer the convex grind. Here’s the reasoning. If you get a flat grind with convex edge bevel, the blade will start off with a certain grit finish. As you sharpen the blade, you’ll only be changing the finish on the edge bevel. Depending on the grit you use, the convex portion might end up with a different grit finish than the flat of the blade. That could look pretty funky, depending on the difference in grits. Now, if you get a full convex grind, you don’t have that dual grit finish problem. A full convex grind is sharpened by abrading the entire blade, so the finish of the entire blade is determined by the grit you’re sharpening with. The whole blade will always have the same grit finish, which will probably look better.

I wouldn’t be too worried about scarring the finish of a full convex grind. As long as you don’t do something crazy, like using a hard stone to sharpen the blade, or using 200 grit SIC paper or diamonds, the finish will be constantly renewed by abrading the entire blade. The convex grinds I use in the outdoors look much better than my flat grinds. Just use wet/dry paper to sharpen the blade, with no lower grit than say 600 grit, and you’ll have a great looking knife.

As far as choice goes, between the PGK and the Straight Hunter, that’s a matter of personal preference and intended use. I generally prefer to carry the smallest knife I can get away with. I don’t enjoy looking like Rambo tromping through the woods. But many people like the “be prepared” philosophy of the larger knife. I will say that I seldom ever need a knife larger than a Straight Hunter in the outdoors, and actually need a hatchet if the Straight Hunter is too small. Then again, I live in the northeast USA. I haven’t got a clue as to what size tools work best in the outback. Think about the size fish you’ll be cleaning, and the size of the game to clean, to determine the size knife you’ll need.

I wouldn’t even bother to worry about handle comfort. My hands aren’t large either, and I’ve never handled a Dozier that didn’t feel comfortable. My Straight Hunter is easily the most comfortable knife in my collection, but I’m sure the PGK is no slouch either.

If the knife was going to do double duty as an outdoor/urban utility knife, I’d most likely prefer the flat grind. But for outdoor only use, the convex grind is easily my preference.
 
Thank you all for the helpful responses - appreciated.

I'm opting for S30V because as well as inland, a fair portion of my knife time is/will be spent on or by ocean. I've got no doubt about the virtues of a D2 Dozier, but corrosion is a worry here. Sure you can work around it, but still... Besides, I'm impressed by what I've heard about S30V per se.

Buzzbait you are correct about the weight. I'd already raised this with Bob and he's confirmed a full convex will be heavier.

But, subject to what I've said about smallish hands (so might reduce the grip a little) that could be an advantage, balance-wise. Although, Bob has indicated he doesn't think balance is a concern anyway. You see my intention is to have a G10 grip. G10 is heavier than the usual Micarta. So...a heavier grip and a heavier blade would counterbalance, kind of thing.

I hope Buzz was sitting down when he read that bit, being the fervent traditionalist he is. To explain, I don't mind the look of black and blue G10 and like the grip it affords, unpolished. A thought in all this was the possibility of accidental immersion of the knife in a mixture of saltwater and marine fuel say - don't think Micarta would like that much. The ironwood is pretty sexy, but don't want to be worried about what might happen to it, either - you know, if it were out late unescorted on a dark night in the middle of nowhere and so on.

With the chopping. Well it is the least of my concerns. Also, there's chopping, and then there's chopping. For full blown chopping , yes I'd take a hatchet also. I've given a fair bit of thought to blade length. As Buzz and others have said before, no knife will do it all and Rambo tendencies are unwise. I am however trying to obtain a knife I'm going to use more often than any other. With that and fish in mind, I thought the PGK's extra length was preferable over the Straight Hunter, although it mightn't be quite as good as the other for the inland stuff I guess. Not a huge difference in either case though.

There'll be no urban use and given what's been said about the finish upon sharpening, full convex it is I think. I think it should be a good marriage with the S30V, also.

I'd better get hold of Thom's mousepad threads...
 
Buzzbait has a webpage about convex sharpening.

Buzzbait,

Would you share that link with Switched? You said that you were switching ISP's and I don't know if the old link was valid.
 
yog :

Convex edge, it will leave a thicker amount of steel behind the cutting edge.
Click to expand...

It doesn't have to, this depends on the specifics of the curvature. You can have a fully convex knife that is in all respects thinner than a flat gound knife. For example when converting a flat ground edge to a convex one you can either (a) hit the shoulder at a more acute angle, which makes the profile thinner and cut better, or (b) hit the very edge at a more obtuse angle, which makes the profile thicker and more durable. Both of these were from flat -> convex, but had opposite results.


If Dozier is grinding the convex ones thicker, then get the flat ground one assuming you want cutting ability over lateral blade strength. There is no reason he has to grind the convex one thicker of course, he could also do a dual convex grind which tapers from the blade to the spine as well as to the edge. This reduces binding in thick materials as you don't have as much "sticking" along the primary. Ref :

http://www.physics.mun.ca/~sstamp/images/blade_profile_parrell.gif

If you want the "clean" nature of being able to hone the primary, you can still do this on a flat ground blade with a convex edge. You lay the blade flat to the paper and then towards the end of the stroke you roll it up slightly. I hone a lot of my blades with this profile in this basic manner as it acts to preserve the cutting profile and keeps the primary free of deep scratches and corrosion pits.

-Cliff
 
My signature now has the links to all of various pages. I just got things moved over last night. Everything has moved, so people will want to adjust their links and bookmarks accordingly.
 
Thanks again guys.

Cliff I was hoping you'd comment. From our email exchanges to date, my understanding is that Bob envisages a full convex on a PGK model to be heavier.

Meaning yes I appreciate that a full convex does not have to heavier/thicker, for the reasons you indicate there. But Bob's conception, in this instance at least, appears to be along that line.
 
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