The blade at the top of the photo was made from a circular concrete saw blade. I cut it out with a thin grinding wheel with out any problems. I thought I had annealed it well, however when I tried to drill holes in it to mount on my grinding jig I could not get the holes drilled. I am assuming the steel is L6. Any suggestions?

Thanks,

Jamie

Concrete blades do not require a steel such as L6,, the inner part of the blade is merely there to hold the attached cutting teeth which do the work. I does need some abrasioon resistance. but not likely a knife steel as we know it.

Some past threads have dealt with this. The most useful solution that I remember was to use a carbide masonry drill bit to drill the holes with.

Concrete blades do not require a steel such as L6,, the inner part of the blade is merely there to hold the attached cutting teeth which do the work. I does need some abrasioon resistance. but not likely a knife steel as we know it.

Rich, I have a chart that says most of these type blades are L6, that's how I came to that conclusion. The edge of these blades are equiped with an abrasive compound that does the work. What I don't understand is why it won't anneal.

Some past threads have dealt with this. The most useful solution that I remember was to use a carbide masonry drill bit to drill the holes with.

Thanks. I'll give it a try.

Those charts aren't worth the pixels on your screen, unless your chart happens to come from the manufacturer of your particular blade.

In steels above about 0.85% C, a slow-cool anneal from well above critical can be counterproductive because promotes formation of large carbides that can be extremely wear-resistant (and thus hard to drill). I don't know if that's your problem, but it's one fairly common problem. I've written about this here before.

When you work with junkyard steel, it is always a gamble, there is the possibility that you have an air hardening steel. I would just pack the blade with jigging putty to keep the heat from running into the blade and then hot punch the holes in the handle.

Have you tried any of the advanced anealing methods in the HT sticky ?

What Matt said! Those charts are often quite erroneous. For example one chart I have seen says that Jackhammer bits are S7---because Machinerys Handbook says that that alloy would make a good jackhammer bit. However S7 costs several times what a medium carbon steel does and so that's what is used. Or most charts say that leaf springs are 5160, however I have run into *1* low alloy strain hardened leaf spring that CAN'T be quench hardened too little carbon.

As for annealing: in knife sized pieces many knife alloys need a helper bar to have enough heat to cool slowly enough---or what I generally do is to heat the piece in the propane forge at the end of the day and then turn it off and block up the door and leave it to slow cool overnight with the thermal mass of the forge supplying the heat for slow cooling.

From some of the reading I have done in the past on some stainless steel you may have actually hardened it from trying to aneal it as if it were a carbon steel. Try sanding it and cleaning it really well. Thro some vinigar on it and see if it gets tarnished that will probably tell you it if was a carbon steel or stainless. I know some of the masonary blades we used at a brick laying job I had were stainless. In all honesty I would just spend the few bucks and buy some new known tried and tested steel from a reputable suplier. I just ordered a 36x1.5x1/8th inch 1095 for less then 12 dollars and 22x2x3/16 O1 tool steel for less then 25 bucks. I might be way out to lunch on what I said about the anealing on that saw blade but I'm pretty sure there are some stainless steel's out there that do harden on a really slow cooling from above critical.

I use a lot of knife grade stainless and all of them are air hardening. I may still have a couple of concrete saw blades laying out back somewhere and last time I looked they had rust on them. The SS I use does not harden from slow coolling down cycle. You can see the specs for 440C, 154 CPM with a quick google to see wot they take to harden. Those specs also will tell you why most folks cannot heat treat SS in home shops.

Is this concrete blade impregnated with tungsten carbide? If so drilling it's going to require a diamond bit. After that the matrix steel could well be too soft to make a decent blade. Abrasion resistant steels can take many forms and many don't require much rockwell hardness.

Frosty The Lucky.