Full flat grind...

[JakeR]

Hi all,

I'd like to know a bit more about this grind and people's experience with it. I now consider convex to be my preferred edge, as i can handle it!

I was Magikelly that it held a sharper edge, but just not as long as a scandi. Im quite pleased i made the mistake between asking for a Scandi and a Full flat as it sounds quite good...stories? Sounds like it's easy to maintain as it doesn't require any accuracy in sharpening as you just lay the whole edge on a stone....Thanks!

Jake

 

[alick]

There are some storming good blades made with a full flat grind (which almost always have a small secondary bevel applied just to the edge).
Spyderco's military folder is one - a classic hard duty folder - so they're not necessarily feeble.

This grind makes a good slicing blade (something that the fat scandi ground blade of a woodlore does not do well however sharp it is). Full flat has lots of "relief" behind the edge. This is another way of saying that it lacks bulk behind the edge which in would force the cut open like a wedge and create resistance as the full depth of the blade goes through the material.

Full flat is very popular for kitchen knives for exactly this reason.

The angle between the two sides of a typical full flat blade is very acute though, often less than 30 degrees. This would make for a very weak edge, so it's normal to put a secondary bevel of say 40 degrees on the very edge to give it greater strength.

In normal use, only the secondary bevel is touched up, but when this starts to become too obvious after repeated sharpening, it's necessary to improve the relief by putting the whole flat of the blade to a stone and taking the primary bevel back down to the cutting edge. The secondary bevel is then renewed, but will be much smaller.

If I remember right, this is all very well covered in John Juranich's book on sharpening which is well worth a read.

It's horses for courses because this grind is inherently thinner than a scandi made from the same thickness stock so you trade off overall strength for better slicing performance.

Cheers

 

[Adi007]

I've got an EKA Nordic H8 that has a full flat with a slight secondary bevel on it ... the thing is scary sharp and easy to sharpen. That steel is Sandvik stainless. The Fallkniven F1 is also basically a full flat with a convex (that steel is laminated VG10) so you have options as to where to go ... however, keeping it a true full flat is going to be hard work!

Nice knife though!

 

[JakeR]

Cheers Alick. Im intrigued now!! I can't see any evidence of a secondary bevel on my Allan Blade. Which is good as it means i now have the option to add one should i feel it necessary.
It's quite amazing what i've learned (learnt?) on these forums. I've never been shown how to properly sharpen a knife. And i now, from what i've learned (learnt?!) here can get any knife i wish to a razor edge...more proof on how valuable this forum is.

Do you reckon it's much of a woodworker?

cheers.

 

[JakeR]

Sorry Adi, posted at same time. Cheers mate. I can't wait now...counting days...sat? Mon? ):

Does yours work as a woodworker Adi?

Jake

 

[Adi007]

Yeah, both the H8 and F1 are great on wood ... the H8 is a stout blade but can be amazingly fine while the F1 with the lam VG10 will cut and cut and cut and cut without needing reharpening.

H8 - http://www.toolshop.de/e/shop/knives_detail.jsp?productID=8005

F1 - http://www.toolshop.de/e/shop/knives_detail.jsp?productID=4056

 

[tomtom]

they dont seem to work for me Adi.. but i cant speak German i work it out.. :?:

 

[alick]

If you think about the edge you put on a chisel or plane blade, the most important thing for woodworking is to have an absolutely flat back to the blade going right to the edge. The "top" side is then sharpened at somewhere between 30 and 50 degrees to the back depending on what you want to cut. Fine angles slice better across the grain but aren't so strong. japanese blades traditionally have no secondary bevel. western woodworkers usually but a small secondary bevel on the top side, but just so that there is less metal to take off when touching up the edge.

With a full flat knife blade, as soon as you put a secondary bevel on both sides, you destroy the idea of a flat back to the blade that is so important for woodworking tools, so no, it's not a very good grind for woodworking.

The scandi edge with two meaty bevels going straight to the edge is much more like a chisel sharpened japanese style, and one of the reasons that that the scandi is so popular for bushcraft is specifically because it is good for woodworking and that's the single most important use for a bushcraft knife.

What I've never tried is taking a full flat ground blade, removing the secondary bevel from one side to make it absolutely flat then using it for woodwork. It could be wicked for paring cross grain like a woodworkers block plane. Problem is it would be assymetric and would only work well in one direction unlike the scandi which can be flipped and cuts equally well in any grip.

Having said that, the modification that I've just described is exactly how many japanese knives are made. Full flat one side with no microbevel, shallow scandi the other. I have a couple, both right handed, and they have terrific performance fine slicing across the grain of soft fragile food. Don't really want to attack a branch with them though ! :yikes:

 

[Andy]

I've found flat grind blades to be ok at wood work. They are harder to control but if you sharpen them at the samre angle tyhen they should cut into the wood with about the same amount of force.

Kitchen knives are rarely flat grind, at least for the good ones. They hollow grind them on a very large wheel to reduce the drag as they cut through the food

A full flat grind will ber better for food prep then a saber grind and make very good skinning knives

 

[JakeR]

Cheers Guys. I'll be interested as to how it works and how long it hold an edge etc...

I'll let you know.

 

[JakeR]

Allan has told me that in the picture he was yet to add a secondary bevel, so it will come with one, which actually, im pleased about. It would be very difficult to add one and get it as perfect as ther pro himself. (And also i have my nice pictures, all i need is my knife ): )

Never would have thought i would be more keen on a secondary bevel than a scandi, im getting more and more pleased i made the mistake! Afterall, i've already had loads of experience with scandi's, something new wil be nice!

Cheers.

Jake

 

[Hoodoo]

If you convex the secondary bevel, it will improve the wood carving ability of a knife a whole bunch, no matter what the grind. The way I look at it, wood is a very dense material and carving it with a knife with a secondary bevel is like trying to force a small blunt wedge through the wood. The smaller the wedge, the easier the knife will penetrate. I have some really thin flat ground knives with very small secondary bevels that do great on wood. Scandis with no secondary bevel or full convex grinds penetrate dense wood with greater ease because the point of entry, i.e., the edge, is very fine. This is less noticeable on green wood because it is softer and less dense than dried wood and therefore easier to penetrate. When you are slicing meat, bread, etc, the secondary bevel is less of an issue imo. Instead of push cuts you tend to use slicing cuts. Toothiness in the edge becomes an advantage. That's why you see so many serrated bread knives.

 

[JakeR]

Thanks Hoodoo, this is all getting too much ): .

Once i work out this camera i'll do a proper review. Could be a full-flat convert...you heard of those? :?:

 

[Martyn]

Thanks Hoodoo, this is all getting too much ): .

Once i work out this camera i'll do a proper review. Could be a full-flat convert...you heard of those? :?:

Here's me thinking you were a convex convert.

How did you plan to sharpen the knife without a secondary edge bevel?

 

[JakeR]

Im confused

Laying it flat on a stone, easy to do, but lots of metal to take off!

 

[Paganwolf]

Im confused

Laying it flat on a stone, easy to do, but lots of metal to take off!

You can get these floppy bits of leather that you put a compound on to hone an edge on your knife i think there called a sharky or something :roll: , try that :rolmao: :rolmao: :rolmao:

 

[rlinger]

I like full-V flat grinds for general hunting and table work. They make good slicers, I believe.

RL

 

[JakeR]

Paganwolf, i thought of it, but some magician somewhere has persuaded me against the idea...not

 

[Martyn]

Im confused

Laying it flat on a stone, easy to do, but lots of metal to take off!

There's a reason why full flat grinds always have a secondary edge bevel, or why scandi grinds never go all the way to the spine. Apart from obviously you'd have to remove metal from the entire surface of the blade in order to sharpen it, aside from that being massively labour intensive, you'd also be left with a wafer thin and increadibly fragile edge (unusable - unless you were a sushi chef, or unless the knife was made of inch thick steel). The bevel angles on a full flat grind are far too shallow to be sharpened to a zero edge. Itd be like using a sabatier kitchen knife for bushcraft - wouldn't last long.

Like rlinger says, full flat grinds make excellent slicers, good for hunting and kitchen work and the profile is seen often on knives designed for this. Adequate for woodcraft, better than a hollow grind, but not as good as a scandi with a zero edge. If the knife is going to be a bushcrafter rather than a hunter, you'd be better off convexing the edge. That's just my opinion of course, you may well love it as is.

 

[JakeR]

I may just do that. What do you reckon would be the best way to convex it? Aren't Gene Ingram knives full flat?

Cheers Martyn.