Flat - Hollow Grind

[gnique]

I just now came up from my shop with a blade that I am working on. I usually make kitchen knives and I grind them with a flat grind. I flat grind because I use such thin stock (1/16 - 3/32) and the blades are usually pretty deep. A typical chef's knife will be 2" deep. I grind the major bevel on a flat platen. I have found that a flat ground blade is very difficult to do right and make symmetrical. Anyway - I have KBO'd (kept buggering on) and have taught my hands how to grind a fair flat bevel. I just recently got a commission to make three hunting knives. What do people DO with hunting knives anyway? Do they stab bears with them or what? Never mind. I figured that I should use a more "manly" blade steel for such a "manly" implement so I dug up a length of 1/8" O1. Pretty thick steel from my point of view. I figured that those guys that hunt may need to dig up a stump or something while they are out in the "dark dismal woods" stalking their prey. So most of the hunting knives and combat knives (what the hell are THOSE things for?) I have seen have been hollow ground. I thought that I would try my hand a hollow grinding. I practiced on some paint stirrers and thought that I was good to go. And it worked!! I got good, symmetrical grind lines and was happy with the outcome and then my brain started to bother me (I often think that my brain has a mind of its own) and I wondered what would happen if I put that hollow ground blade on a flat platen and mixed the two geometries together (I am plagued with a degree in civil engineering - I can't help myself). I got an AMAZING combination of grind lines! What I need to know from you guys is if this is something new or have I rediscovered something that has been proven to be stupid over and over since the beginning of time? Help me out here - have any of you guys tried this?

 

[JasonSCarter]

I just recently got a commission to make three hunting knives. What do people DO with hunting knives anyway? Do they stab bears with them or what? Never mind. I figured that I should use a more "manly" blade steel for such a "manly" implement so I dug up a length of 1/8" O1. Pretty thick steel from my point of view. I figured that those guys that hunt may need to dig up a stump or something while they are out in the "dark dismal woods" stalking their prey. So most of the hunting knives and combat knives (what the hell are THOSE things for?)

Are you serious? lets not be a troll... :thumbdn:

I got an AMAZING combination of grind lines! What I need to know from you guys is if this is something new or have I rediscovered something that has been proven to be stupid over and over since the beginning of time? Help me out here - have any of you guys tried this?

What you have there is a modified Granton edge grind. The granton edge (air pockets) are ground into the blade to create air pockets! Less effort is used to slice the food.

Jason

 

[MeDoctor]

I've read of folks starting with a fairly shallow hollow grind done on a 10" (or even a 14") wheel, then converting it to a flat grind.

 

[AcridSaint]

I hollow grind all of my knives, even the ones I flat grind. I have flat ground from 8" hollow up to 14" hollow. Sounds like the flat didn't get get carried all the way up the blade. If it looks like the first reply then you may need to work on hollow grinding some more. No offense.

 

[flatgrinder]

I've seen a combo grind before.

Here's a picture of my 100+ year old Khukuri:

Overall, it's convex ground, but the front portion (tip to halfway down the blade) is hollow ground in the middle (but the edge is still convex) for increased speed when chopping. It's 1/2" thick at the ricasso!

This thing is old as heck, but it works! I used it to take an old tree down a few years ago and due to the weight, balance and geometry -it's incredibly efficient. I didn't even sharpen it.

You have a good idea there, nothing wrong with thinking outside of the box! See if it works for you, then go from there. :thumbup:

 

[gnique]

That's what I did! The grind I did looks almost exactly the same! I really like the look and though I have not yet completed the knife it looks to me like it will cut and slice just fine. Thank you for posting that picture. I will post a picture of the drop point hunter I am working on when it is finished. Thank you again for the picture. I knew that I was not the first one to try this method. I am going to pursue this direction and find out where it leads. Nicholas Jasper