What happened to the convex edge?

while we're at it.....I have another question Ed...about forge reduction. You said you got your best results from the most reduction. What is happening to give you those results? Is reheating the key? Or does the reduction even out (align) the grain better?

Would you get the same effect if you started from a large ingot of your own making?
 
Dan: I strongly believe that the amount of reduction by forging at the right temperature and using the right methods dictates the nature of the resultant blade. We have a number of experiments designed to indicate how much reduction by forging provides the extreme benefit. I do know that I have never had a blade forged from a 2' ball out cut blades forged from 3" balls.

I just conducted an experiment where in blades were forged (all from 5 1/2 inch round stock), the same billet, each blade with increasing thermal cycles and found no limit reached when the final blade had been subjected to 5 times the thermal cycles than the first. Each got better!

Rex had located a large round bar, something like 30" diameter. Our intent was to have it turned down to various sizes and then blades forged from it to indicate how much was the optimum. Unfortunately a pending divorce and resultant lack of funds dictates the experiment is not going to happen for a while. Then I messed up my shoulder and that has severely limited my knifemaking. It may be a question to be answered by those who attend our high performance seminars and seek to find the answers. We do know that a 200 point reduction by forging results in wow stuff. The forging must be well planned and no errors to influence the results.

All experiments indicate that the greater the degree of reduction by forging can result in greater degrees of performance. There are many variables, I just spent two months on one experiment and learned a lot. It will be reported in Blade.

The thing to remember is that there is no limit to how far we can go, we have not found the end of the trail and I believe that the vast number of variables leaves plenty of room for experimentation and each experiment leaves new questions to be answered.
 
Thanks for that answer, Ed.



Do you do any heat cycles on your balls/bars before reduction?
 
What I have learned most from this thread, is that I have alot to learn.
I think it is a never ending process, with alot of facts ,opinions, and some hype, and bs mixed in. I have found that there are so many different views on what
makes a good knife that it can be confusing,especially for a new knifemaker.
I guess you learn everything you can, test everything you make , and make
what works in your opinion. then make it to the best of your abilities.
 
Daniel: I looked back at your question about reduction and grain allignment. I thought I answered it, but may not have. Back when I was using ball bearings, I tried to allign the grain before I started working on the ball, sometimes I missed by a few degrees. When I missed, some beautiful swirls appeared in the etched blades that originated through the less than perfect grain allignment. These swirls did not seem to affect performance, at least the way we test. In a knife blade slight variation's in grain allignment may not be extremely significant. This is probably due to the fact that working down a large mass results in a lot of allignment that may partially negate earlier errors. They were beautiful.

When working with the John Deer load control shafts as a spirce of 5160 I do not start off with any thermal cycles other than those that occur during forging. If my supply of 5160 was straight from the mill I might work it differently.

With the 52100 We soak the billets (3 inch or more) at a temperature just above critical for 2 hours for every linear inch to the center, bring them up to temp slowly, then allow very slow cool down times. I lost some of the ultra high levels of performance through this process, but now start the steel all the same and will hopefully learn how to develop the variables that led to the super stuff by plan rather than some unknown variable. The greater perfromace we found was wow stuff, but one #%&^^#@* variable also caused the wheels to fall of on one experiment that was one of the most devistating events of our (at least my) voyage. I was actually ready to quit making knives. I had figured that we were ready for the next stage of experiments, then the wreck. Now working back to where I thought we were and one less unknown variable to contend with.

Times are good again and much greater understanding has resulted from the wreck. Lots of seemingly insignificant events can come together to make a whole that is greater than the parts. When we share information we get a lot of flack, but like my friend HDT said long ago "All this worldly wisdom was once the unamiable heresy of some .... man".

I will return to your other thougths and see if I have neglected to answer any questions.
 
Dan, I have never hollow ground a blade ~ all mine have been flat except a couple of convex, so all I have is second hand thoughts. I have a friend that is an acomplished maker of over 30 years that told me that the only hollow ground blade that he thought was worth a darn is just as you described. BTW, Karl Schroen convexes his blades (or at least used to) so that they are thinner at the spine than at center mass for the same theory that you have.

Some one posted about cutting cheese with different bevel grinds. I personally find it much easier to slice cheese with a flat ground knife than with a blade that is ground on a 8" wheel. I find that the hollow ground blade wedges more, not less. YMMV. I think that a blade ground on something like a 20" wheel and with a convex edge would be pretty slick though. :)
stevo
 
my biggest complaint with plain hollow ground blades is that they are ground that way almost to the edge. I've yet to find any production type knives that had more than 1/4" of bevel on them beyond the hollow grind. Does anybody know of anyone who has created such a grind? (and tested it)
 
Thanks Dan, you just let my cat out of it's bag...;) But seriously, the grind that you are referring to is precisely what I am going to put on some chef's knives that I am developing. I am going to have a very shallow hollow grind to 1/4" of the edge, between a 24" to 36" radius with the last 1/4" of the blade being reserved for a convex edge. I can't wait until I'm setup to get one made for testing! I would love to hear of anyone's experiences with the same. I have all of the drawings done, just need to get the shop setup after moving again!
 
how far out is this testing going to take place? days, weeks, months, years?

I would be very interested in the results.

But in a chef's knife, it's more about overall grind thickness, is it not? I agree that a convex edge would be good for material separation, particularly if kept thin. I've put a full flat grind on most of my kitchen knives lately and find that they perform probably 80-90% as well. Not good enough for me, of course, but good enough for my customers. I still prefer a small convex bevel for ease of sharpening/maintenance as well as better material separation.
 
Dan,

Unfortunately it's probably going to be in the weeks to months category before I can get my shop setup and the prototype completed. Hopefully it will be much sooner.

In regards to your point about the thickness of the grind... I couldn't agree with you more. To date, my kitchen knives have all been finely flat ground with a full taper and a convex edge. I love the performance. The best overall edge for kitchen use that I have come up with so far has been to put a polished convex edge on the knife and then give it a few licks on a fine India stone to give it some "micro serrations". The edge seems to out last a standard beveled edge, but I have yet to quantify that with side by side testing. I'll give a full report as soon as I am able to come up with something solid.
 
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