The varied convex grind

bindlestitch

bindlestitch

Joined
Oct 23, 2006
Messages
1,461
Hey guys,
Andy and I were talking about this grind I've been using on my "utility" type knives. I call it a "standard" grind because that's what I put on a knife when a customer doesn't specify what type of grind they want.
Basically it's a convex Randall grind.
Here's what it looks like.
grind%20standard%20grind%20pic.jpg


Here's the theory behind it:
Advantages:

The low grind height near the ricasso area is very much like the 1/4 height grind, meaning it's super strong. This is an advantage in a woods knife as much of the notching/carving work is done right in this spot. The middle of the blade has decent height for slicing but still enough metal behind the edge to be an excellent batoning knife. The tip, with it's full height characteristics, excels at slicing when skimming off extra wood or slicing potatoes around the campfire. I prefer this grind over all others for a general/hard use knife. It just can't be beat for utility purposes when used correctly in my opinion.

Disadvantages:

Only one that I know of, the tip isn't as strong as the 1/4 height grind. But with a little common sense drilling with the tip is no problem at all.
Click to expand...

For the last year or so I've been trying to come up with the super knife. Like (I'm sure) every other maker before me I came to the conclusion that it's not possible to make such a knife. There are specific grinds, stock thickness, blade heights, profiles, etc. for specific chores. This grind is the compromise I settled on. It does most things well but does nothing exceedingly well.

So the point of this thread is to start a debate of your thoughts on the benefits or detriments of the grind. I'm interested in everyone's opinion, good bad or indifferent.
Sorry for the wordy post.:(
Thanks in adavance,
Iz
 
Send me one and let me test it - then I will let you know. ;)

Seriously though - do you have any closer pics of blade only? I am intrigued.

TF
 
TF,
I don't really have anything that shows it clearly, honestly.
Maybe these will show somewhat

On this one you can see the plunge line runs only to about half height.
4133963816_52e09edd5e_o.jpg


When view from the top (it's hard to see in this pic) there's a close to normal looking distal taper you get from a full height grind.

4133202313_2b04516825_o.jpg


This one it's hard to tell on because of the sharpened top edge. But you can see the low plunge line and sorta see the taper at the tip.

4336761466_7be4d0a958_o.jpg


Iz
 
Oh yeah, in the interest of comparrison, this is a regular full height grind. You can see the height of the plunge line is a lot taller and the distal taper at the tip is close to the same as the varied grind.

4259742191_abd007f4df_o.jpg


Sorry for the cruddy pic.
Iz
 
The only drawback that I could possibly see being a factor would be if the slope of the primary bevel within the carving area makes for a fat enough grind to prevent the blade from biting deep enough into the material being worked on. I see that in a lot with knives like the RAT Cutlery RC-5. The thickness of the blade, combined with a relatively low grind height makes for a blade that isn't quite as good for fine work like carving and pressure cuts. A big part of that however has to do with the thickness of the blade on that knife. Depending on the thickness of the stock you're using, it might not be a factor at all. Anything less than say 5/32" thick probably wouldn't cause any kind of problem. On the other hand, I could be slightly off base here. It certainly wouldn't be the first time that I was surprised by a blade's performance. This is all purely based on just looking at pictures. Either way, it looks awesome and I'd love to play with one and check it out first hand. Great looking knives.
 
OK. I'm glad you started this thread. I liked your thinking, then kinda had the same doubts Dylan expressed. The area near the hand is for notching and carving as you said. I would think you would want that as thin as possible for performance sake. The only time I think a convex needs to be steep is in a chopping belly area on a larger knife (or axe). Even then, a little thick goes a long way to impeding performance.

Off track. I actually think this is a drawback of the Nessmuk hatchet. I don't use the thick side at all. The thin side chops better, and hasn't ever suffered damage (this is on my little Cegga head). So the thicker side, ehh, I don't really need it. Does anyone carve, or do fine work with a double bit hatchet? Not easy, or comfortable, why not use part 1 or 2 of your Nessmuk trio to do those tasks. Actually the double bit part kinda scares me also. I'm always expecting to sink it into a stump, then, being a dumbass, sit on the sharpened other side.

This is what interested me about the grind when I saw it on your website. Your take was opposite of mine. I know you know your convexes, so I found that interesting.
 
This is what I like so much about this place (BF and this subforum in particular), freedom to express different opinions without getting any "you're an idiot for thinking that way" responses.

My thoughts are along the lines of Andy's. Has anyone done exactly the opposite of what you've laid out here? In other words, start with a tall grind for doing detail work close to the handle and then shallow it out towards the tip to maintain a heavier edge for chopping. The latter would compromise the performance of the tip for drilling though; however, Andy's penetrator tip would go a decent way in offsetting that.

I really like these threads. They keep the creative juices flowing:thumbup:
 
Andy, you and Dylside are correct. It's a poor fine carver in that area.
I need to re-word that write up. I don't carve much because I suck at it, heh.
What I really meant/mean to say (and I'm sure there'll be some disagreement here too) is I like the thicker grind for feathering. For fuzz sticks and shaving. The steeper contour give me the ability to go deep or shallow when I'm taking off shavings for tinder.
I use mainly harder woods (willow, sycamore) for the bow and drill so sometimes I use a baton to carve out the ember notch. Here's where I like a little extra meet just in front of the plunge.
So yeah, you are exactly right, the grind there is to steep to be a good carving knife.
That's one of the hard things about making knives ain't it? I mean, I know how I use a knife but a lot of the time I do things totally different than others do. So if I make a knife to my standards it may be reversed to others. That's why these topics are fun, you get to see things from other perspectives and learn.

Jc,
I don't know if that's been done or not. It could be done, might be worth a try and maybe doing some testing. It'd be really cool on a bigger chopper, something like Andy's bow leg. Maybe a little smaller than that so you could use it as an intermediate knife.

Keep this stuff coming , guys. This is how million dollar ideas are made.:D:thumbup:
Iz
 
For anyone interested I took a few pics when I got done rough grinding today.

I left the layout dye on so you could see the grind line
4356092451_7b4af67baf_o.jpg


4356838962_2a21e86ba7_o.jpg


You can see that it's flat and lower as you get to the plunge line
4356092511_f53007b7a4_o.jpg


Here's the full height tip
4356092833_b3c6b0ddb9_o.jpg


The tip has almost the normal distal taper of a full height grind
4356839250_23f11f395b.jpg


of course the taper would be more prominent on a wider or longer blade.
Any thoughts? Good/bad?
Thanks for looking,
Iz
 
Great lookin work Iz. Can't wait to get my paws on one.
 
JC in SC said:
Has anyone done exactly the opposite of what you've laid out here? In other words, start with a tall grind for doing detail work close to the handle and then shallow it out towards the tip to maintain a heavier edge for chopping.
Click to expand...

A fairly common mod for machetes is to put a scandi edge near the handle for fine work, then changing to a stout convex for chopping at the "sweet spot." It's a similar philosophy to what you've stated here. I've never done it, but I bet it's effective. The thing is, it would only work on a larger, "choppable" knife, not something small like this one.
 
sircantaloupe said:
I love the concept - it's well thought out. Just gotta put it out there for proving.
Click to expand...

Thanks, man. I agree, I've got a few out to users now and have done limited testing myself. I plan on making one for myself in the next few weeks (I hope) and I'm gonna do extensive testing with it.
Iawoodsman uses the hell out of his so I'm getting feed back from him, too.
He's got a video review on his youtube page if you're interested in his take.
Iz
 
JC in SC said:
This is what I like so much about this place (BF and this subforum in particular), freedom to express different opinions without getting any "you're an idiot for thinking that way" responses.

My thoughts are along the lines of Andy's. Has anyone done exactly the opposite of what you've laid out here? In other words, start with a tall grind for doing detail work close to the handle and then shallow it out towards the tip to maintain a heavier edge for chopping. The latter would compromise the performance of the tip for drilling though; however, Andy's penetrator tip would go a decent way in offsetting that.

I really like these threads. They keep the creative juices flowing:thumbup:
Click to expand...

Sorry to bump this up but I took your suggestion Jc and went with it. This grind is based on your suggestion and on Mac's (pict) machete mod video.
Thanks for the inspiration, guys.
4654493507_3b817dbc7d_b.jpg


I haven't tested this one yet like I have the other one so I'm not sure how effective it'll be.
Iz
p.s. If anyone is interested in how the other grind performs I did a quick vid making the one stick fire here
http://www.youtube.com/watch?v=cSEbJSjqlzA
 
Wow. Now thats neat and new, and I've not seen it before Iz. That leaves the meatiest part at the sweet spot, and the sliciest part in the notching spot. Great idea.
 
BTW, as always, bumping and anything else you want to show on my forum is cool with me.
 
Very interesting indeed. I for one will be eagerly anticipating the results of your testing.
 
Fiddleback said:
BTW, as always, bumping and anything else you want to show on my forum is cool with me.
Click to expand...

Andy,
I can't tell you now much I appreciate that, brother. I really do. I've been hesitant because I don't want to seem like I'm trying to get sales here. I just love your knives and like being involved in this forum. You're one of the guys who has inspired me most in knife making so I'm careful about what I post and how often out of respect for you.
You rock, man.
Iz
 
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