View Full Version : Concrete cutting blades - any good?


Markus40
04-24-2004, 12:20 AM
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!

rlinger
04-24-2004, 02:13 AM
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

Ed Caffrey
04-24-2004, 10:19 AM
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.

Markus40
05-06-2004, 01:07 PM
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

Crex
07-01-2004, 08:30 PM
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.

shgeo
07-02-2004, 10:40 AM
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.

AUBE
07-02-2004, 02:13 PM
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 :p

Wildman
07-02-2004, 05:19 PM
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

Crex
07-03-2004, 08:11 AM
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!

Markus40
07-09-2004, 03:59 PM
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

Wildman
07-09-2004, 05:15 PM
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.:)

Crex
07-10-2004, 07:21 AM
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!

JGardner
07-10-2004, 08:23 AM
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 (http://www.primosknives.com/articles/scale_prevention/no-scale1.htm)


Justin

Markus40
07-20-2004, 02:07 PM
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

stoneman
07-20-2004, 09:40 PM
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.

Crex
07-20-2004, 10:37 PM
Mark,
The blade snapping like that is not a bad thing. It indicates you are getting the hardening temp pretty well on the nose. I don't think there's many of us out here that haven't snapped a few. I do it just to test unknown steels all the time (just don't make them into a blade first!). There is a small window of opportunity to straighten a blade with some steels after the quench, but it's very small and not worth the risk to me. Since I forge all my blades I always have a heat source ready for redo if necessary during the HT process.

Are you normalizing of the steel after grinding? It will make a world of difference in how the blade responds to HT. Take the blade up to critical, remove and hold in still air until the color goes flat black. Allow to cool further until it's cool enough to touch. Repeat the process total of three times and then go for the HT. You can also take the blade through the annealing process after normalizing (go to SEARCH) but I haven't seen any significant difference with the saw blade steel doing this.

I always make sure there's no warp before the quench with a quick look down the spine. With practice you can do it while in motion to the quench tank. If you still get a warp, reheat and straighten while hot. You have caused uneven stress during the grinding process. On a stubborn piece try just an edge quench, sometimes that will allow you to salvage the work.

I do the normalizing process while I'm forging the blade and after I prepare the blade for HT. I strongly suggest adding the step to your process.

Carpe Ferrum!

Markus40
07-21-2004, 11:34 AM
Carl:

That was invaluable information. I've never normalized steel in all my years of knifemaking. I guess I'm just lazy, or didn't quite understand what the extra work (and oven kilowatts) was all about. Obviously I need to improve my processes. I've never tried edge quenching, but I've read a lot by Wayne Goddard about how he does it. Last night I relented and opened the shop doors again, found the broken blade (snapped mid-handle) and salvaged it by arc-welding a piece of mild steel all-thread on as a stick tang. So all is not lost! We'll see how it turns out.

I agree with your first statement that I'm probably hitting the hardening thing right on. I examined the break, and the grain was tight and clean. This steel really does harden up nicely. I don't know if you have found this to be the case, but even annealed, this stuff seems to grind slowly--say, in comparison to annealed L6 or files that I've used before. What temperature would you recommend annealing at? I'm wondering if I'm getting it soft enough.

I'm taking one of these 28" blades to an industrial laser shop to have them computer-cut a zillion blanks for me all at once. That will save me lots of time hacking out rectangles and then spending so much grinding time on the profiling.

Mucho thanks again for the advice!

Mark Russon
Computer Programmer
Knifemaking Hobbyist
Woods Cross, UT

Crex
07-23-2004, 06:32 AM
Mark,
Glad to be able to help. Let's face it, unless you get a lab analysis of the steel you don't really know exactly what type of steel you have. The way you described the break and hardness, I'm not sold on it being 41xx series. If it's still tough after annealing then your annealing process is not right for that particular steel. Many of the alloy steels require a multi-stage annealing to get them to "dead soft". A lot of alloy steel aslo "air hardens" to some extent so just bringing up to critical temp is not all there is to the annealing process. Best results come from very slow cooling down from critical. Most simple Hi-carbs respond well to over night in a bucket of vermiculite that has been preheated with a chunk of hot scrap steel. Bigger the mass of the scrap the slower the cooling process.

Critical temp varies from steel to steel. The magnet test has always proven satisfactory for me. I do my HT in my forge and go by mag and color to determine the critical temp, so I don't have a set temp # to give you. Also I do very little grinding other than to clean up profiles. I do 85 to 90 percent of my shaping and bevels with hammers. Can't say that my hammer has noticed any problem with the normalized steel hardness :).

On the normalizing, I usually take the unknown steel to critical temp (non-mag) and then take out and let cool in still air. If you are doing this in an airconditioned shop or with a fan on, you need to turn these off so that the air is still. I handle everything by the tang and move slow and deliberatly, clamping the end of the tang in a nearby vise and let cool to touch before doing it again. If this doesn't work for this particular steel, suggest slipping it into that bucket of vermiculite for a couple of hours then pull out and air cool to touch.

How much will it cost you to have the blades laser cut? You might come out better in the long haul to buy a good "port-a-band" band saw and a supply of bi-metal blades. This will cut up any masonary blade quite well (ifyou avoid the diamond matrix) and you have a very versitile and usefull tool for other projects and needs. I find mine quite indespensible. A little planning and attention to cutting and you should be able to cut your blanks down to pretty close to profile with very little effort.

Carpe ferrum!

Markus40
08-15-2011, 02:52 PM
I thought it might be fun to follow up on this thread. It has now been 7 years since I posted about using concrete-cutting diamond saw blades for knife steel. I have made hundreds of knives since then, and I'm still using it. I think it's great material. I still don't know exactly what the composition of the steel is, but what I've learned from a practical standpoint is enough. I've been told the steel is everything from 1050 to L6 or L7, or possibly 4130 or 4140. What I know is that there's enough carbon to make a fantastic, tough blade if you do the heat treatment right. I've settled on only using the larger blades, I think they're about 28" in diameter and 3/16" thick. The smaller, thinner blades don't seem to have the same quality of steel. I still cut it out into rough rectangles with a 4" angle grinder and cutting disc. Then I anneal it in my oven. It often warps during this process, but is easily straightened in the vise. At this point I can finish the profiling with my metal-cutting bandsaw, or with a grinder. It drills very easily. After I'm done grinding, I stamp the tang with my logo, and normalize the steel. I've gotten the best results by taking up to almost non-magnetic, then air cooling in still air until I can touch it. With large blades, I do this three times. I find that this keeps the blades from warping in the quench. Then I do the hardening. For small blades, I heat them up just past non-magnetic and quench them in plain water THREE times. That seems to be the magic number. More than that, and I don't get any more benefit. Less than that, and I don't have quite the maximum grain refinement and toughness. I've tried using brine as a quench, which is obviously pretty aggressive, and that has worked for small utility blades. But I've had too many blades crack, so I steer away from brine most of the time. For larger blades 5 inches or longer, I quench in oil three times. I like cooking oil discarded from deep-frying turkeys. It smells good after you quench! Finally, I draw the blade with a torch just along the spine to color. I have done all kinds of cutting tests, bending the blades, break tests, file tests, spark tests, and feel pretty satisfied that I'm getting the maximum performance from this steel. I'd love comments from anyone who is also using this steel. Maybe I'm missing something. But this has made consistently great knives of all kinds for years. And since I have a ####load of it, I'll keep using it!

Here is some of my work: http://www.wasatchmountainknives.com

Ed Tipton
08-15-2011, 05:38 PM
Markus40...My comment is limited to the problem of warping. Generally speaking, all forging or grinding should be done as evenly as possible on the blade. If you're grinding predominately on one side more than the other, that could be the cause of the warping. I forge my blades....and I have never tried to work with any saw blade materials, but in my forging and heat treating, I have found that treating each side in a similar manner helps with the warping. I usually forge to my satisfaction, do a "very close to finish grind", and then normalize the blade prior to the heat treatment cycle. This is done in an attempt to reduce to the greatest extent possible all of the residual stresses which have been introduced up to that point in my process. Using this technique, I have had very little warping or cracking in my blades. To date, all of my blades have been either 1080, 5160, or 52100 steel, and I use Parks 50 as a quenching medium. I have tried both heated and ambient oil with basically the same results, but Ed has indicated that it is not necessary to preheat the Parks 50 oil. Also, by using a worn concrete or masonry blade, there is no way of determining what the stress level is in the blade when you receive it....which leads me to think that it is even more important that the steel be normalized prior to the heat treat cycle. The tendency to warp or crack is caused by internal stresses that reside within the steel. Anything that you do to introduce stress needs to be cancelled out before heat treat.

PaMtnBkr
05-23-2013, 04:01 PM
Very interesting journey you have been on with this material! Really got my attention because there is a concrete cutting company near my house!! May have to play with some of this steel! thank you for doing your intitial leg work!! BTW-You make some AWESOME knives!! Loved your site!! DonO

tuskbuster
05-24-2013, 01:10 AM
i use a lot of teh old blades as ive been keepin after they get wore out ,old brick mason.use em mainly in my little hunters and hog stickers that people want and dont wanna put down the money for the ,KNOWN STEEL. i do all my grinding post HT and dont have many problems.

Gary Mulkey
07-25-2013, 09:32 AM
Mark,

I don't use used steel and thus never worked with this particular steel but remember when straightening any blade that it is under a lot of stress immediately after quenching and is most likely to crack at this time.

Try quenching until barely black (slightly under the nose) and check for straightness. You should be 800-900 degrees at this time and you can straighten it then without so much chance of failure if you do it quickly enough. I wouldn't recommend straightening any time at less than 500 degrees. (Once you have it straight then continue your quench.)

Also, check the blade closely before H/T for an even grind. Often warping is simply having more steel on one side of the blade then on the other.

Good luck.

Gary

John Walters
10-21-2015, 04:01 PM
Hi

I'm new to the forum, but I've been making knives for about 30 years here in Hawaii. I was taught by Tom Mayo and helped by Vince Evans and Ken Onion on tempering and handle design.

I've been making knives and machetes from concrete cutting steel for about 20 years, ever since I got a consistent supply. I differentially heat treat all of my blades and aside from the occasional warped or cracked blade (probably 1 in 30) I have never experienced any problems, it's my favorite steel. I was going to send some pictures, but couldn't figure our how to get them on the site, assistance would be appreciated.

stezann
12-01-2015, 08:48 AM
rotating blades with diamond or carbides tips should be of any steel capable to hold impacts, not necessarily to hold an edge.

there is a straightforward testing, i suggest you to make a straight razor out of it and see if it is good for shaving...if yes it is a good knife steel, if not maybe could be used for choppers and axes.