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

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  #16  
Old 07-20-2004, 09:37 PM
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Crex Crex is offline
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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!


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  #17  
Old 07-21-2004, 10:34 AM
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Markus40 Markus40 is offline
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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
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Woods Cross, UT
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  #18  
Old 07-23-2004, 05:32 AM
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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!


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  #19  
Old 08-15-2011, 01:52 PM
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Markus40 Markus40 is offline
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Concrete saw blades - 7 years later!

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

Last edited by Markus40; 08-15-2011 at 02:04 PM. Reason: Misspellings, omissions
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  #20  
Old 08-15-2011, 04:38 PM
Ed Tipton Ed Tipton is offline
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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.
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  #21  
Old 05-23-2013, 03:01 PM
PaMtnBkr PaMtnBkr is offline
 
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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
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  #22  
Old 05-24-2013, 12:10 AM
tuskbuster tuskbuster is offline
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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.
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  #23  
Old 07-25-2013, 08:32 AM
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Gary Mulkey Gary Mulkey is offline
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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


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  #24  
Old 10-21-2015, 03:01 PM
John Walters John Walters is offline
 
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Concrete cutting saw blades for knives

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.
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  #25  
Old 12-01-2015, 07:48 AM
stezann stezann is offline
 
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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.
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