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

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  #1  
Old 04-23-2004, 11:20 PM
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Markus40 Markus40 is offline
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Concrete cutting blades - any good?

I have had generally good success with using sawblade steel for knives in the past. I recently came across a large supply of used concrete cutting (diamond tip) blades about 3-4 feet in diameter and 3/16" thick. It's really tough stuff. I cut some test strips, heated them up to about 1600 degrees and quenched them. They broke in the vise (after about 30 degree flexing) with a clean snap and very fine grain. Are these sawblades generally good stock for knives? I've heard mixed things about them in other forums. I have a lot of this stuff, if it's worth working. Is it high enough in carbon, and how should I heat-treat it?

Thanks!
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  #2  
Old 04-24-2004, 01:13 AM
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rlinger rlinger is offline
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Snaping at 30 degrees proves hardness. I know nothing about the steel you speak of but it is hard and brittle after your quenched. Drop you temperature down to 1475 - 1500 F, quench again, temper at 400 F and try the snap test again. Take it to 35 - 40 degrees and see if it returns straight.

Let us know. Be careful and do not try the snap test again without first tempering 1 hour.

RL

Last edited by rlinger; 04-24-2004 at 01:16 AM.
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  #3  
Old 04-24-2004, 09:19 AM
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Concrete saw blades that are diamond tipped are made of either 4140, or 4130, depending on the diameter. Small diameters are 4140 and larger diameters (anything over 20" are 4130) Quenched in water or "super quench" they make useful large chopping type tools if the edges are left fairly thick. I would not consider them suitable for small knives simply because the edges would not stand up in thinner cross sections.


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Old 05-06-2004, 12:07 PM
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Maybe there's hope...

Ed:

I took your suggestion about the concrete blades to heart, and was going to give up, but decided to give it one last try since I have such a huge supply of this steel! I cut out a test blade of about 4" and hollow ground it. By the way, the concrete blade diameter is about 21" and 3/16" thick. Then I water-quenched it at just past non-magnetic (my earlier tests were oil-quench). It came out with a slight warp in the handle area, but some stiff bending in the vise straightened it out. It had a very tenacious resistance, and didn't break. I didn't do any tempering on it, because it didn't seem particularly brittle. A new file skated across its edge with very little bite, which really surprised me. So I cleaned up the scale and put a nice edge on it. Then I proceeded to test it. I cut through a 2x4 with axe cuts. No visible edge damage. Then I did about 50 1/2" rope cuts before it started to slow down. It needed a minor stone dressing and it was off again. Seems like maybe there's something to this steel... am I missing something?

Mark

Last edited by Markus40; 05-06-2004 at 02:52 PM.
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  #5  
Old 07-01-2004, 07:30 PM
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Mark,
I to have access to an almost unlimited supply of large masonary/diamond blades. I have found that some blades respond very well to a good HT and some just fair. Unfortunately the used blades rarely have any referenceable mfgr. mark so I test a slice or two from each blade I cut up. I forge all my blades so flavor my response in that direction. Because I cannot be certain of the steel composition wihtout expensive lab testing, I only use the better responding stock for forging kitchen knives. They will still outperform the average store bought blade (and I include the overpriced Henkels in that list). I have also made a few fillet knives from this steel that are in their third year of heavy field testing (I can't get my buddies to let me have them back for inspection).

I have also come across an interesting phenomina in that some masonary blades have proven to be composit steel with grain structure very similar to wood fiber or micro cable damascus. This particular steel proved to have very good response to an O1 HT and turned out to be very tough to break. The edge holds up fair to good and is quite easy to bring back on a strop. The fiber pattern only shows up after HT (etching the masonary blade, as is, produced no pattern). Got all kinds of opinions from other makers but none that I'd feel comfortable in passing along. No offense fellas, just no hard facts.

The steel also welds up quite well with 10xx series hicarb steels for use in patternwelded steel projects. Use it to learn with and have fun with it. Just be honest about it if you use it in a blade you sell or give away. Blades, good or bad will speak for themselves.

Oh yeah, if you decide to cut them up don't waste time with a torch or chisel. Buy or borrow a Port-a-band Saw and put in a bi-metal blade. It'll slice like mild steel, just use a little forthought when you plan your cuts and stay away from the diamond matrix.


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Last edited by Crex; 07-01-2004 at 07:35 PM.
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  #6  
Old 07-02-2004, 09:40 AM
shgeo shgeo is offline
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I looked into lapidary blades last year because I had a source. I found that there is a wide range of steels used. Some are low carb, some 1050 and some L6. European one are sometimes 15N20. I couldn't get info on the ones available to me and experimented with lackluster results, so gave up on it. Good steels of known composition are too easy to get.

By the way, the material impregnated with the diamonds is often a Cobalt alloy like Talonite. I made up a few blades with the diamnod edge incorporated and gave them away as presents.


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Old 07-02-2004, 01:13 PM
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AUBE AUBE is offline
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Quote:
Originally Posted by shgeo
I looked into lapidary blades last year because I had a source. I found that there is a wide range of steels used. Some are low carb
hmmm i see potential marketing towards the Atkins crowd here
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  #8  
Old 07-02-2004, 04:19 PM
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I have been using the larger (24" and bigger)blades for a couple of years now and find if I normalise them the HT like 01 they come up hard and tough. Some of the stock has to be tempered a little higher or the edges chip if made too thin but overall I have had a lot of fun with them.

mick
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Old 07-03-2004, 07:11 AM
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I think Mick hit the mark with the "have a lot of fun with them" statement. The price is right, experimenting is an excellent learning experience, and it is a lot of fun. Let's face it - most of us got started pounding steel more for the fun and romance than anything else. It's hard hot work and requires determination, concentration, and a healthy amount of good nature (otherwise we'd laugh and/or criticize ourselves right out of the shop).

I personally enjoy experimenting with unknown steels as some can be quite surprising. I do all kinds of destructive tests with each new source of mystery steel before I start making a blade to do edge cutting test with. On the large masonary blades we are talking about here, I test material from each blade. So far I've gotten good results from 75% of the blades I've tested. I can live with that. The rest wind up in my scrap pile for fabricating other useful stuff. I hate waste!

If you're in it for the money and are trying to make a living at being a bladesmith then you really don't have the luxury of much time to experiment. So don't bother with "unknowns".
If you're in it because you love it and can't seem to quit, then by all means have fun and learn how to make the "unknown" steel work for you.

Carpe ferrum!


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  #10  
Old 07-09-2004, 02:59 PM
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Carl:

Thanks (and to everyone else) for your comments regarding masonry blades. I have spent a considerable amount of my scant spare time in playing with this stuff. I do this as a hobby, but have just received an order for a batch of 6 hunting knives for Christmas that I'm going to fill using this material. I have gained pretty high confidence in it. I just need a little more advice. I've been puttering with knifemaking for about 15 years, but I'm sure that my skills are far beneath your own. I've given away dozens of knives over the years, but I'm just now getting confident enough to sell them.

Just for a little background, I do only stock removal blades, and have done most of my work with old files and pieces of various kinds of sawblades (L6 I believe). Even some small paring knives made from table saw blades. Like you, I have an almost unlimited supply of the masonry saws. My buddy cuts concrete for a living, and gives me his old blades ($1,000 bucks new!) when he's done with them. Most of them are the 29" blades that are 3/16" thick. In keeping with Ed Caffrey's comments, my research has found that this stuff is probably 4130 or 4140. Lower carbon than, say, a Nicholson file, but absolutely TOUGH stuff. I'm convinced that the secret lies in proper heat treatment.

You mentioned treating it like O1. Can you give me more details on hardening and tempering? I've made 4 knives with this stuff now, and have done a water quench instead of oil. It just didn't get hard enough with oil. I haven't seen any indication of cracking from the water quench. Would brine be better? I'm tempering at about 400 degrees for a couple of hours. My cutting tests, though not extensive, have performed pretty well.

Like you said, cutting this stuff up with a torch was not good. I resorted to a metal-cutting disc mounted in my circular carpentry saw, and that does a good job. I hack it into nice rectangular blanks and then anneal the pieces in an oven at about 1500 degrees and let them cool overnight. They get some significant scale, but it cleans up nicely and is very grindable after that.

Any more comments would be appreciated before I turn out my six blades for sale! Thanks.
Mark
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  #11  
Old 07-09-2004, 04:15 PM
Wildman Wildman is offline
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http://ajh-knives.com/metals.html
http://www.knives.com/heatreat.html

These sites have all the info you will need to get started. Depending on the grind you put on the blades you may need to play with the temper temp'. The blades are not always going to be the same exact makeup as as if the steel was bought but you can figure out what it acts most like and just go from there.
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Old 07-10-2004, 06:21 AM
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Mark,
Mick tagged some good resource material, but you'll notice there is some variation between sources as to HT temps and procedures. Use them as guidelines and adjust from there, once you start testing your results. Remember you are working with much thinner material and different geometric crosssections than for what the standards tables are written.
Try a brine quench and test the results. I have been using a heated (150 deg) olive oil/mineral oil quench with good results but I have also used warmed water with good results. Every once in a while I get a blade that HT's like L6, in that it doesn't get hard immediately in the quench but test it again a little later and it had gotten much harder.
Ahh....the mystery!
You can also try varying your tempering heat 25 deg at a time to find a possibly more satisfactory temper. I usually don't go above 375 on the masonary steel.
Happy experimenting!


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  #13  
Old 07-10-2004, 07:23 AM
JGardner JGardner is offline
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I hack it into nice rectangular blanks and then anneal the pieces in an oven at about 1500 degrees and let them cool overnight. They get some significant scale, but it cleans up nicely and is very grindable after that.
Check out the tutorial on scale prevention by Terry Primos. I have used PBC compound for about a year with great success.

PBC Scale Prevention


Justin
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  #14  
Old 07-20-2004, 01:07 PM
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Markus40 Markus40 is offline
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Carl:

Since you seem to be the guy with the most experience with these big masonry blades, maybe you can help me. I don't think I'm getting the heat treatment right. I made a beautiful blade with about an hour of grinding on it, put it in the oven and got it up to just past non-magnetic. Then quenched it in plain water at room temperature (outside--probably 70 degrees). It came out with a slight warp. I put it in the vise, and tried to pull it back to true, and it snapped cleanly in half. Crap! I threw the pieces on the shop floor and haven't gone back since last night. My other tests with plain strips of this material quenched in water didn't seem so brittle. I have been able to straighten them after quenching with no problems. First of all: is it better to pull the blade to straighten it, or bang it with a hammer? But more fundamentally, am I using the wrong quenching medium? Is oil sufficient for this 4140 steel? I was worried that it wasn't getting hard enough. Also, should I temper before trying to straighten? What are your experiences? I'm trying to get this just right.

Thanks,
Mark
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Old 07-20-2004, 08:40 PM
stoneman stoneman is offline
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I am no expert, but I believe you should temper the blade before straightening. After the Heat treat Hardening Quench, the blade will be hard, but also brittle. Tempering should lessen the chance of it breaking.


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