Old Knives Re-visited

[tippit]

I have never really liked hollow ground blades.  With said I did get a 10" wheel with my new grinder just to try hollow grinding.  So I found 2 old early clunker knives that I had forged a while back.  They were beautiful when I had made them & didn't know any better     Anyway they were just thrown into a box and forgotten about.  Since they were poorly shaped and as thick as the original bar stock, I decide to learn on them rather than waste the time forging nicer blades.

Well, I've changed my mind on hollow ground blades.  It seems to be easier to do than a flat grind and on a thick blade it really brings the edge down to a slim profile.  Without a great grinder my old knives just take a back seat.  Always something new to learn...Doc
 

[Shaun]

Looking good Doc. I like the way you left the finger stop thick on the upper one.

[JC]

Yeah....junk knives....just send em on Doc and I'll dispose of them for ya! I will say, those are nice looking tools....but you certainly have improved your skills since these early models. Really liking that new grinder aren't ya?

[AZStickman]

Tippit.... What's the difference between Flat ground and Hollow ground??..... Terry

[BigRonHuntAlot]

Here is some info on the Hollow ground blade...

Hollow Ground Blade

A knife blade with concave beveled edges created by starting midway or lower from the top of the blade and grinding or tapering each side of the blade thinner toward the bottom or cutting edge by grinding a inward curvature. As the blade is ground the slight curve (concave) grind creates the "hollow" area referenced in the blade. Produced with either a fluted pattern or a beveled pattern, a hollow grind provides a very thin and exceptionally sharp edge that can be easily sharpened when necessary. It is a type of blade that is excellent for slicing due to the sharp edge, but not for chopping activities since the higher impact of the chopping action dulls or may chip the thinner blade. Unlike the taper ground blade that is made from a single piece of metal which results in better balance and stability, the Hollow Ground Blade is not durable enough to withstand higher impact activities.


Here is some on the Flat ground Blade.

Flat Ground Blade

The type of blade with a straight "V" cut ground into the steel edge. Varying in depth, the Flat Ground Blade can be made with only as very slight "V" cut or a longer cut that tapers slightly from higher up on the blade and extends downward toward the cutting edge. Knives with a flat grind can be used for cutting as well as chopping activities since the blade is generally very stable.

[robtattoo]

A = Concave or hollow grind. Created by grinding on a wheel, different diameter wheels produce differend severities of grind. The smaller the wheel, the deeper the hollow grind. A really big wheel, produces a hollow grind that is *almost* flat. Usually has a small secondary edge bevel, but not always.

B = Full Flat grind. Created by grinding off a flat steel or ceramic platen. The grind goes fully from the spine of the knife, almost to the edge, where it it almost always has a secondary edge bevel (no edge bevel would require sharpeing the entire flat surface of the knife - I've never seen a full flat grind without a secondary edge bevel).

C = Convex ggrind. Usually created by grinding the steel on a "slack belt". This means no platen, so to some extent the grinding belt deforms to the steel, producing a convex edge (*the same principle as a hoodoo hone). The true full convex grind, doesnt usually have a secondary edge bevel - a grannyB for example.

D = Scandi Grind. Many methods to create this style, but typically, the edge bevels only go 1/3 way up the side of the knife. This creates a very acute or "fat" bevel, which usually does not have a secondary edge bevel. Note the difference in "angle of attack" between this and the full flat grind.

All of these different blade geometries (or combinations of them) produce knives with different charicteristics

[JL]

I keep flipping between flat and hollow ground blades. Being I use both production and custom knives that use both grinding methods, I feel certian types of steels work better with different edges. The real hard stuff works great with a flat grind and softer steels benefit from a hollow edge. Maybe thats just my perception but makers tend to follow that train of thought also. Have you done any rockwell hardness testing on your blades Jeff?

JL

[hormoan]

Hi Jeff

     I think I'd like to own the lower one, is it for sale. Even with all the dust on it?    PM me it so looks like it needs a new home.

                    Brent

[AZStickman]

Thanks Guys....... Terry

[JasonV]

Doc, could we talk you into a brief 'how-to' for hollow grinding the blade - for those of us who dabble in metalwork -tips, pointer, precautions..(I've made a few with flat ground tapers, but I'd like to try it)

BTW, you "clunker knives" look better than my best work!!!  :D    :D    :D

[tippit]

I don't rockwell hardness test.  I do two other tests:

1) Brass rod deflection on edge:  If you roll the sharpened edge on 1/4 brass rod, it should deflect (bend) and come back to original shape.  If too soft, it will stay bent.  If too hard, it will chip.

2) Critter skinning:  If it skins more than 1 bear without sharpening, then it's just right!
Doc

[Marvin M.]

I agree.  If those were "scrapped", I'll voluteer to come carry out your trash.  I'd be proud to own either one of those blades.

Maybe someday I'll have the leisure/toos/gumption to try my had at one.  In the mean time, I just drool over the pictures on here.

Marvin "knife envy" M

[tippit]

Jason, If you really want to know how to hollow grind or true flat grind, there are 2 great DVDs.

1) The Fine Art of Hollow Grinding by Johonny Stout.  He grinds on a wheel with a rest.  I find it easier to grind freehand on the wheel.

2)Flat Grinding with Harvey Dean.

Both men are A.B.S. Mastersmiths.  Look up (www.ccinstructionalvideos.com).  They have other DVDs on all sorts of great things in bladesmithing from sheath making to decorative filing...Doc

[tippit]

Thanks Big Ron & Rob for posting those descriptions.  See ya in Texas  

[DarkeGreen]

I think some of the comments on hollow ground blade were true at one time when lesser steels were used. Today hollow ground knives are the nuts (good thing) of knife blades. It give you the ability to balance the knife better, provides a more durable and sharper blade, leave the knife with backbone, and with good steel chops better than any other design you'll ever use. Hollow ground blades are the be all, end all of blade design!

[JC]

Dang, and to think...20 generations of Japanese sword makers "wrong", just like that   :rolleyes:  

With respect Darke, in some instances, the proper tool for the proper job is still appropriate. There are some situations where hollow ground is not the answer. Otherwise, why wouldn't every high end knife maker do it? Chisel/flat ground is very popular for survival/UDT/extreme combat knives, most cleavers are convex ground for strength...etc.

Now, as far as broadheads, I've been very happy with both flat and hollow grind. Specifically flat grind from a file on a Wensel and hollow ground from my Simmons wheelie sharpener on my Deadheads. I don't think it would be possible to measure which would be a "superior edge", at least at killing animals.

[tippit]

I love the look of a nice flat ground blade and a hollow grind that goes to the top of the spine.  But a hollow grind that only goes 1/2 way up the blade or a more primative convex grind just doesn't appeal to me.  

The important thing is what appeals to ya' awl (there I go again practicin' for hunting hogs in Georgia    So I guess that's why there are so many different styles of knives & grinds out there.

[tippit]

PS:  I'm just having a blast figuring all these things out.  Maybe I should go back to working full time instead of 3 days a week.  Then all these new ideas wouldn't be so pressing....Naw!

[robtattoo]

Sorry DG, I'd have to dissagree. Look into any CCCT (Competetive Cutting Circuit Tour) knives & you'll find that they're all convex ground. The competitions include free-hanging rope cuts (from 1" up to around 6" rope bundles)-1cut, Chopping into 2x4-the record for a complete cut is somewhere around 2 secs, paper slicing etc.... all witout a resharpen. Honestly mate, try a convex sometime, yu'llbe converted for good!  :D

[robtattoo]

Originally posted by tippit:
 
The important thing is what appeals to ya' awl (there I go again practicin' for hunting hogs in Georgia     So I guess that's why there are so many different styles of knives & grinds out there.

Damn right!