MEMBER ITEMS FOR SALE
Custom Knives | Other Knives | General Items
-------------------------------------------
New Posts | New PhotosAll Photos



Go Back   The Knife Network Forums : Knife Making Discussions > Custom Knife Discussion Boards > Knife Making Discussions > High-Performance Blades

High-Performance Blades Sharing ideas for getting the most out of our steel.

Reply
 
Thread Tools Display Modes
  #1  
Old 08-17-2005, 08:48 PM
Coutel Coutel is offline
Master
 
Join Date: Jul 2002
Location: NE North Carolina 27909
Posts: 816
torque wrench test

Hi.

I am curious to know how much difference in force is required to flex identical sized blades with different/selective hardnesses, ...... one fully hardened, one edge hardened with soft back and one full hardened but with the back drawn to medium hardness/spring.........??

For instance, does it take less force to flex a soft spined knife as it does one that is fully hardened (and tempered)......

I was thinking how to measure this difference ....maybe a large torque wrench would work.

Has anyone done any tests along these lines?

If I can find me a wrench then I will have a go.


__________________
Kevin Davey
Reply With Quote
  #2  
Old 08-18-2005, 10:05 AM
Kevin R. Cashen Kevin R. Cashen is offline
Skilled
 
Join Date: Feb 2003
Location: Hubbardston, MI
Posts: 324
Kevin:

If you are just flexing, there is no need to go through the trouble of testing, it was all figured out long ago and is a formula that is used everyday in engineering and desgining things with steel. You may have heard me spout off before about "youngs modulus" also known as "modulus of elasticity" . The formula for steel is as follows- E=30X106psi. (that 6 should be superscript), but you can ignore that gobbledy goop, since I hate math, it makes my head hurt in a bad way. What is says is that every material has a ratio for how far a given volume will stretch from a given psi. of load. 30,000 is an approximate for steel, but close enough for our work, so in tensile load, steel will elastically stretch 1/1000 of an inch for every 30,000 lbs. of applied. *

This does not translate directly over into a bending test, but it does lay down the groundwork to let us know that when we are dealing with flexing alone, heat treatment is entirely irrelevent. If you have two blades with EXACTLY identical cross sections, one fully annealed, the other fully hardened, it will take the exact same ammount of pressure to flex them since the material is still steel. In order to change stiffness and flexing, you need to change the cross section of the piece. If it takes 30,000 psi to elastically stretch a square inch of steel 1/1000" then making it a square 1-1/4" will take a heck of a lot more and making it 3/4" will take significantly less, but playing with the martensite, pearlite, cementite etc... inside that steel won't make any difference.

If you start any bending at all, suddenly the heat treatment will begin to have an effect on the results.

Forgive the geek factor here but heat treament doesn't come into play until after the "proportional limit" is exceeded. The proportional limit is the point in tensile loading in which the ammount of deformation strain will exceed the ammount of stress being put in. Below this point everything is proportional so when the load is removed the steel is able to return to true. When this point is exceeded, deformation will continue beyond the amount of load applied. Have you ever stretched something and stopped to see it stop moving as well, but at one point if you stop there will still be stretching in the center of the piece? This will usually be followed by necking or narrowing in the area still moving.

I am not discouraging your tests, since nothing confirms a concept better that seeing it with your own eyes, but if your blades are identicaly shaped you will need to actually bend them to see a difference on your torque wrench.


* what the modulus actually says is that it takes 30,000,000 psi to stretch steel to double its own length, but that doesn't translate real well into the real world so we work it down into numbers that do. I detest having to get this technical over such a simple coversation, but I have found that there are always yayhoos waiting in the shadows to jump on any opportunity to correct the smallest of details and prop up their egos by by finding an "i" you failed to dot or a "t" you failed to cross

Last edited by Kevin R. Cashen; 08-18-2005 at 10:21 AM.
Reply With Quote
  #3  
Old 08-18-2005, 11:25 AM
Coutel Coutel is offline
Master
 
Join Date: Jul 2002
Location: NE North Carolina 27909
Posts: 816
Thanks for replying and posting this in some detail Kevin..I really appreciate it.

So, if I understand right,....everything else being equal.... the heat treatment process will make no difference to the amount of force (pounds) that need be applied to move the steel ..be it bending annealed steel or snapping it because its fully hard.

Thanks.

(if I get hold of a torque wrench it will be interesting to test the theory).


__________________
Kevin Davey
Reply With Quote
  #4  
Old 08-18-2005, 11:56 AM
Kevin R. Cashen Kevin R. Cashen is offline
Skilled
 
Join Date: Feb 2003
Location: Hubbardston, MI
Posts: 324
Not at all. Here is where the conversation always gets confusing, it seems like certain words may be interchangeable but they are not. What it comes down to is "bending" is entirely different from "flexing". The term "flexing" assumes that it will return to true as soon as the load is removed. "Bending" means that the steel will not return to true when the load is removed. This is why, despite how techno-geek it may sound I preffer terms like "elastic" and "plastic". Some words are not just for confusing or impressing people they are just the most accurate way of stating things without confusion.

All dimensions being equal the amount of force to break hardened steel will be much greater that the force required to bend or even break (in tensile circumstances) soft steel. An edge quenched blade will bend farther without breaking but will bend very easy when compared to a full quenched blade that will require much more force to deform, and that deformation will occur at such a high level that it will be very close to the point where things will just break. But just flexing a blade and allowing it to return to true will require exactly the same force regardless of heat treatment.

One thing that can be blown apart here is the bad terminology of saying that an edge quenched blade is "stronger". That is patently and totally false (unless you count impact fracture as deformation then it could be said to have imapct "strength" but I would preffer to say impact toughness to avoid confusion) . One can safely say that a pearlitic spine is "tougher" than a fully hardened one, but the full quenched blade, by definition is the "stronger" of the two because it will resist deformation. A soft spine will easily deform so it cannot be said to be stronger, but it can have more impact toughness.

I have tried to dot all my "i" and cross the "t's" but I am sure some slide rule jockey could find something here

Last edited by Kevin R. Cashen; 08-18-2005 at 12:08 PM.
Reply With Quote
  #5  
Old 08-18-2005, 05:05 PM
Coutel Coutel is offline
Master
 
Join Date: Jul 2002
Location: NE North Carolina 27909
Posts: 816
Just when I though I understood..I didnt


but your second posting is comparable to what I was thinking the effect would be.....

thanks.


__________________
Kevin Davey
Reply With Quote
  #6  
Old 01-18-2006, 11:54 AM
Ed Fowler Ed Fowler is offline
Steel Addict
 
Join Date: Feb 2004
Location: Riverton Wyoming
Posts: 275
I have not read all the posts yet, but thought I would comment on our recent gizmo, made a jig with a bolt welded on it, the jig bolts onto the tang of a blade, like a sandwich, put the torque wrench on it and tried with a differentially hardened low temp forged 5160 test blade. It required over 115 foot pounds to flex the blade to 90 degrees. This was about a 4 1/2 inch medium weight pronghorn with the modified Michael Price grind. The torque wrench is easy to apply and may lead to some insight for those who wish to check for themselves.


__________________
Ed Fowler
Reply With Quote
  #7  
Old 01-22-2006, 10:24 PM
Thingmaker's Avatar
Thingmaker Thingmaker is offline
Steel Addict
 
Join Date: Jun 2002
Location: Washington County, Oregon
Posts: 160
How 'bout a longer blade? A shorter one? A thicker one? A thinner one? A wider one? A narrower one?

Being a slide rule jockey myslef, I kinda like to see more than just one number in vaacume. Is 115ftlb per 4.5" a good number? A bad one? An average one?


__________________
Perfection is a process, not a goal. Perfection is a journey, not a destination.
Reply With Quote
  #8  
Old 01-23-2006, 10:21 AM
Kevin R. Cashen Kevin R. Cashen is offline
Skilled
 
Join Date: Feb 2003
Location: Hubbardston, MI
Posts: 324
Quote:
Originally Posted by Ed Fowler
I have not read all the posts yet, but thought I would comment on our recent gizmo, made a jig with a bolt welded on it, the jig bolts onto the tang of a blade, like a sandwich, put the torque wrench on it and tried with a differentially hardened low temp forged 5160 test blade. It required over 115 foot pounds to flex the blade to 90 degrees. This was about a 4 1/2 inch medium weight pronghorn with the modified Michael Price grind. The torque wrench is easy to apply and may lead to some insight for those who wish to check for themselves.
Ed, the gizmo sounds useful for your testing. I find myself compelled to ask if the blade flexed to 90 and return completely to true or did it take 115 ft. lbs to bend to 90. It is easy to confuse the two terms. I only ask because I see potentially helpful numbers for the proportional range (true elastic flexing), but the information provided on the test piece only applies to the yield point (taking a set) and beyond. I think this is what Thingmaker is getting at with his question. To satisfy his curiosity one could simply give the cross-sectional area versus the length of the portion flexed, with no mention at all of forging or heat treatment and then the flexing numbers will make total sense. Or give the angle at which the blade first took a set and attach the forging and heat treatment information to that.

You can see how confusing it can be simply by allowing the terms "bend" and "flex" to become interchangeble, and us bladesmiths have been bad about that little oversight.
Reply With Quote
  #9  
Old 01-23-2006, 09:02 PM
rhrocker's Avatar
rhrocker rhrocker is offline
Hall of Famer
 
Join Date: Nov 2002
Location: Uvalde, Texas
Posts: 3,117
I was watching a ABANA DVD of a demonstrator named Beau Hickory. He was pretty far above my head (or at least I thought he was, I wasn't sure if he was brilliant, or yanking everyone's chains). At one point, he used the phrase "modulus of elasticity". I knew then, that he was a big put on, because no one would have come up with that silly phrase.
Er... ahem...until I just read Kevin's post above and found out that it's for real. Now, I take everyone serious (cept TM)


__________________
Robert Hensarling
Uvalde, Texas




Hensarling Custom Knives

Reply With Quote
  #10  
Old 01-24-2006, 04:30 PM
Kevin R. Cashen Kevin R. Cashen is offline
Skilled
 
Join Date: Feb 2003
Location: Hubbardston, MI
Posts: 324
Quote:
Originally Posted by rhrocker
I was watching a ABANA DVD of a demonstrator named Beau Hickory. He was pretty far above my head (or at least I thought he was, I wasn't sure if he was brilliant, or yanking everyone's chains). At one point, he used the phrase "modulus of elasticity". I knew then, that he was a big put on, because no one would have come up with that silly phrase.
Er... ahem...until I just read Kevin's post above and found out that it's for real. Now, I take everyone serious (cept TM)
Careful, who's to say I'm not full of ##@$ as well? Actually I have been known to spread some manure occasionally, I always do it with my tongue planted in my cheek, however. But you are correct, nobody could make this stuff up. Young's modulus (modulus of elasticity) is not a relative or abstract concept that only works in one shop and not the other, it is as fundimental and undeniable as Newton's laws of motion. But the sad and even frightening thing is that I have only encountered a handful of smiths that are even aware of it. The vast majority of bladesmiths just do not understand that heat treating has nothing to do with a blades flexibility, it only determines where and what happens when the flexibility is exceeded.
Reply With Quote
  #11  
Old 01-24-2006, 06:13 PM
Ed Fowler Ed Fowler is offline
Steel Addict
 
Join Date: Feb 2004
Location: Riverton Wyoming
Posts: 275
As soon as I can find it and figure out how to post a drawing of the knife with measurements etc. I will. Right now I am buried in other knife stuff.


__________________
Ed Fowler
Reply With Quote
  #12  
Old 02-04-2006, 11:43 AM
Burke Burke is offline
Steel Addict
 
Join Date: Aug 2002
Posts: 231
Here is the drawing of the knife that Ed is refering too. 5160 Test Blade post.bmp

Bill


__________________
Bill Burke
ABS Master Smith 2008
Reply With Quote
  #13  
Old 02-04-2006, 12:16 PM
Ed Fowler Ed Fowler is offline
Steel Addict
 
Join Date: Feb 2004
Location: Riverton Wyoming
Posts: 275
Thanks Bill for posting the drawing. I can't read the numbers as they came across, so here they are again.
top to botton
Ricasso : .257
.254

moving right .250
.195
.125
third column . 240
.205
.140
blade from spine to cutting edge 1.135
next column .234
.220
.151
fifth column .221
.210
.145
tip .165
length from tang to tip 4 7/8th. All measurments in inches.

All of the bending or flex as you wish to call it took place between the line measuring the distance form spine to cutting edge and the plunge line. This is where it was designed to flex by nature of what I call the modified Michael Price grind. We had to place the blade into the vice to about the depth of that line as the vice could not hold below that line due to the taper in the blade.

When you have to apply this kind of lateral force to a blade it gets kind of dangerous, blade slip can put a guy on the floor real quick.

The blade initially took a set at about 45 degrees.

The blade was edge quenched, the first temper line was about 1/3 up from the cutting edge.

We first did a 90 degree flex or bend, then a 180. At 180 degrees or a little bit more the hardened portion gave way in the form of a tear along the grain boundaries. It is significant to note the word 'tear' break would have been through the grains.

At the top of the tear the seperation split into a Y along the temper line. The softer area above the temper line did not seperate. The blade returned to about 30 degrees of bend on its own.

Other testing included rope cut, 400 cuts and would have done more.
Tip did not deform when punched into mild steel.
I pounded ont he spine with a 2 lb. hammer driving the tip through some very hard
aged cornual bone and the tip did not deform and could cut the ridges of my index finger print patten.

This was a blade we forged during a seminar, I had to rush the thermal cycles due to time pressure and it did not have the advantage of full 24 hour cycles between normalize, blade smith anneal, hardening or tempering or it would have done better.

This was 5160 steel that we purchased from Dan Grey who has it advertised on Blade Froms.


__________________
Ed Fowler

Last edited by Ed Fowler; 02-04-2006 at 12:22 PM.
Reply With Quote
  #14  
Old 02-04-2006, 05:21 PM
Coutel Coutel is offline
Master
 
Join Date: Jul 2002
Location: NE North Carolina 27909
Posts: 816
180 degrees is a 'U shape, being bent in half.....
The most bend I could put in a mild steel bar held in my vice would be around 120 degrees before the vice obstructed the bend... how do you bend a knife that size to 180?.. is it the preacher bar thats 180 degrees or do you reposition the blade in the vice so it can be squeezed?...just curious.

Thanks.


__________________
Kevin Davey
Reply With Quote
  #15  
Old 02-04-2006, 06:34 PM
Kevin R. Cashen Kevin R. Cashen is offline
Skilled
 
Join Date: Feb 2003
Location: Hubbardston, MI
Posts: 324
Thanks for going through the trouble of posting those numbers, they are not just valuable information if we are to consider comparisons within the proportional range for such a blade, but they are probably really great info for folks who love or may wish to collect your work.

Forgive me I do not wish to be a pain in the behind but I am just finding myself more confused with the terms you are using. I cannot draw any conclusion that I personally would find useful because the word bend and flex are still being used interchangeably, when they are unavoidably exclusive.

I think I follow you when you say, ? This is where it was designed to flex by nature of what I call the modified Michael Price grind?, I am with you so far since the grind would be the most significant factor in flexing the blade with given amount of force and having it return to true. But if the blade took any kind of a set, which you say occurred at 45 degrees, then you have lost me again because we have definitely exceeded the yield point and can no longer be flexing at all.

Now was the first test, which I will assume was a bend test, done on the blade in an annealed condition and subsequent tests done after the edge quench, for comparison purposes?

This subsequent test was once again either a bend or a flex, but I cannot tell from your description. Did it return to true or did it take a set at any point? If it did bend, was it a tight kink, or was it a gentle curve over the length of the blade? The closer to a tight angle you get, the more tensile forces were involved and the better it speaks for the condition the material itself, but the less I would like the heat treatment personally, but there are always tradeoffs in this stuff .

The word ?tear? and your definition of it, has confused me once again(don?t worry every year that goes by find me all the easier to confuse ). While fracture analysis can appear a bit complicated between ductile fracture and brittle fracture, I will assume from the way you describe it, that it is brittle fracture. This is because I have always observed and seen described, the two types of brittle fracture as intergranular and transgranular separation and cleavage, and you mention things happening between grains as apposed to within them . So I assume (and I know where that often gets me ) that under microscopic examination that you found it to be intergranular separation, which would make sense, I just haven?t seen it explained as ?tear? versus ?break? before, although in layman terms I guess I have mostly referred to intergranular separation as ?breaking?, heck it is all fracture to most.

But when the test was done the blade did still maintain a 30 degree set so I am going to risk concluding that this was a bend test and that the ft. lb. measurements are for taking the blade beyond the yield point and even, to some extent, failure, which heat treatment will determine the position of on that scale, in relation to true flexing, where it yielded and where it would fail.

As for the rope cuts, and the steel stabbing, I understand that that would indeed have nothing to do with the topic of torque wrench testing but is handy information for those interested in your blades, with which you are again most generous.

Thank you for the time to provide us with a better insight.
Reply With Quote
Reply

Tags
blade, forge, forging, hunting knife, knife, knives


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


All times are GMT -5. The time now is 06:35 PM.




KNIFENETWORK.COM
Copyright © 2000
? CKK Industries, Inc. ? All Rights Reserved
Powered by ...

Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
The Knife Network : All Rights Reserved