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Main Boards => PowWow => Topic started by: tippit on February 08, 2007, 02:05:00 PM
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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
(http://img.photobucket.com/albums/v110/tippit/Knives/IMG_2440.jpg)
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Looking good Doc. I like the way you left the finger stop thick on the upper one.
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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?
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Tippit.... What's the difference between Flat ground and Hollow ground??..... Terry
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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.
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(http://i4.photobucket.com/albums/y110/robtattoo/grindtypes.jpg)
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
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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
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Hi Jeff
I think I'd like to own the lower one, is it for sale. Even with all the dust on it? :bigsmyl: PM me it so looks like it needs a new home.
Brent
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Thanks Guys....... Terry
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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
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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
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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
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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
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Thanks Big Ron & Rob for posting those descriptions. See ya in Texas :)
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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!
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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.
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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.
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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!
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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
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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! :thumbsup:
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Yep different "strokes" or in this case grinds for different folks. Lookin good Doc, like I said Buddy keep reachin up and havin fun. :thumbsup: :thumbsup:
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Nice blades as always Tippet. Bring a few of them "dogs" with you in May and I'll show you where to dispose of them.
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Hey Doc you do know I collect clunker knives. :rolleyes: So if ya wanna donate those clunkers to me I have room. I would share one with JC. ;) :readit: .Shell is yelling at me right now telling me how Shameless I am :goldtooth: :biglaugh: . A But really Doc you make a great knife. As does Mr.Campbell and Rob and Loyd Lippert.<><
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Thanks for the link Doc - I ordered both.
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Jason, You'll get a lot out of them. I still go back and pick up tips I've missed on previous viewings. I flat grind like Harvey Dean does on the right side of the platen but I hollow grind like Johnny Stout except freehand without the rest...Doc
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Since you won't sell one of your knives, we HAVE to work out a TRADE for one someday!!!!
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Brian,
I am waiting on some very fine files to finish up the Hurley Predator knife. I want to do a design on the entire blade. This knife just needs to be special. Once that is finished, I'll send it up to you for it's sheath.
Now I was thinking maybe if you are willing, I'd send 2 more knives for you to make sheaths. The plan is:
1) One will be mine (cause I'd like to have one of your sheaths too!)
2) The other will be yours
You choose which one you want. Just a small thank you for doing those St Judes sheaths...Doc
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Lookin' good Doc!
What are you grinding on? I've been looking at the Coote grinders. Just 'cause KMG etc. are waaay out of my range.
You don't know what you started!!!
Then again, mebbe you do :thumbsup:
Larry
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Doc,
That would be AWESOME, but I feel like you would be getting the short end of the stick.
WOW!!! I feel like I just won the Lottery!!!
I can't believe I am going to have an honest to goodness Tippit Knife!!!
WOW!!!! Did I say that yet? LOL!!
I am actually kind of speechless which is rare for a Baptist Preacher!!
Thank you is all I can muster right now.
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Brian,
The stick is more than even for making those St Judes knives look all prettied up :) Thank you.
Larry,
Did you get set up with a forge & have you been pounding hot steel? It kinda gets contagious just ask my wife :) I did get a KMG with all the goodies thanks to Mr Campbell & his horse trailer. But shoot look at all the money I'm making...oops I forgot I don't sell anything! Anyway I'm having fun. That grinder is so nice, I can't believe I was actually making knives with that sorry old Sears grinder. Sorry I'll miss you at the JLMBH...Doc
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Oh boy . . you bet!!
Been forging & beatin' on hot steel since last March! Got the whole business for forging goin' on right now except the grinder.
Can't seem to justify the $$ to the Ms. I actually used a KMG for a little while & IMO they're at the top of the list!!
Wish I could've taken it home w/ me! I know exactly what you mean about the small grinders. I'm using a 1x30 Delta right now . . it's killin' me!
I was really lookin' forward to seeing you @ the BH too. Have a whole lot of forgin' stuff to talk about (read that as questions).
Man . . I thought knapping was addictive! Nothing compared to this!
Thanks for the starting push!
Larry
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Larry, Send me some pictures of your stuff. I'd really like to see it.
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Oh come on guys! A 1x30 Delta is all you really need (just leave me my delusions, please!) I visited a knifemaker up in Long Lake, NY this last summer... he's got himself a Bader! I tried not to drool too much on his stuff, but watching him grind out a knife in no time flat was cool to see.
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Jeremy, That's the whole thing...how quick and nice those grinders work. I'm now spoiled but what the heck, I'm too old to be grinding my fingers on that old Sears :)
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I'll jump in here for Larry, I bought one of the Coote grinders like 13 or 14 years ago and it's still going strong. I mounted a 2hp motor and did a little modifying on it to fit my needs and am happy with it. Done a ton of grinding on it Picked up a variable speed KMG when I got Doc's so I'm in hog heaven now. Oh and I still use one of them old Sear's occasionally too, hang in there Jeremy ;)
Dang this is great to see all you guys getting excited about forging and grinding knives. :thumbsup: :thumbsup:
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Originally posted by JC:
Dang, and to think...20 generations of Japanese sword makers "wrong", just like that :rolleyes:
You do know what the advantages were right? At one time many of their methods were done out of necessity due to the poor quality of steel available to them. Even the folding of welding steel to made blade was desired back then. Today it simply isn't required or desired for function. We still do it because we are romantic and think it's purty. ;)
One reason not everyone does it is because it increases manufacturing cost. Hollow grinding a blade it consider more difficult to perform than all other grinds...or so I've been told. :)
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http://www.balisongcollector.com/grinds.html
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But then again, if you have money to spend on CNC equipment...
CNC Autoload Hollow Grinding
Our 6 Axis auto loading CNC Hollow grinder will produce a high volume of hollow ground blades at minimal cost to the customer. 4 - 5 step grinding processes which can take 4-5 setups can now be done in one setup. Complex shapes or curved blades are a simple proposition. Tooling is inexpensive and can be developed and running in very short lead times. Material can be ground hard or soft with predictable and repeatable finishes. A large capacity high volume paper and magnetic filtration system keeps coolant clean and contaminant free to prevent burning and premature wheel wear. Wheel sensors constantly adjust for wheel wear and compensate the control for less that .0002 variation per grind.
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basically most companies won't use top end steel because tooling cost to much and it wears very quickly. They also don't want to spend the time required which can be as much as 10 x more effort. If you use low quality steels by todays knife blade standards you need to all of your statements are true. If you use the best steel and have the time and money...none of them are.
I do agree about the differerent strokes though.
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From another high end manufacture that uses VG10 V30 ATS34 and such for blades.
7. Hollow Grinding
The next step in blade making is the hollow grinding process. Here, blades are ground (computer machined) to achieve a desired shape and slope from the top of the blade down to the cutting edge at the bottom. Predominantly, we use a "semi-hollow" grind to create an edge that will be sharp out of the box, retain its sharpness, be easy to re-sharpen and enable the blade to maintain its strength. Robotics is used for grinding to achieve a consistency not possible with hand grinding.
These cross-section diagrams show the four most common grinds used for knife blades.
Semi-Hollow - Creates a nice balance between a sharp edge and overall blade strength. It is the most common grind used today.
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The way the rest of us do it :)
(http://img.photobucket.com/albums/v243/jindydiver/knife%20tutorial/1011.jpg)
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i use old chopsaw blades stacked 7 deep, being cheap like i am its the only way for me, besides i get them free, but im running a 5 hp 3 phase grinder motor i got at a yardsale for $10.00. loyd