Drilling rotary cutter blades

I have a 48" Club Clipper belly mower on my B. I could not find blades for it. I fownd some Woods blades on RCS that will work. The only problem is they need new holes drilled in them. They are really hard. I have tried high speed drill bits, cobalt bits. Nothing works. I have thought about heating them before drilling, but I am not sure what this would do to the temper of the blad.It would also ruin the bit. Any suggestions.

Heat might be OK too.  If you soften the center area of the blade, the cutting are will still hold an edge.  Might wollow out the holes though, just all depends on many things..

Long shot suggestion but a machine/tool and die shop with a punch press to punch the correct size hole?

I was told several years ago that if you heat it red hot and let it cool slowly, then that softens the metal. I've never tried it. I don't know if slowly means let cool back to ambient or put in warm sand or ash. Then after drilling your holes, heat it back up and then quench it in something. Again, I don't know if that means water or oil or super quench. Let us know what you end up doing. 

I agree with concrete bits. May need ear plugs, it will squeal like a pig caught in a fence .                MACK

Let a machine shop do them in a vertical mill and use carbide cutter. Much better , cheaper and damn sure safer! HTH Tracy

Whoops!

Concrete bit is an interesting idea.  Carbide tip to cut the hard metal, but steel body so not so likely to break.  Carbide is a bugger to grind though, diamond does it the best.

Thanks everyone. Now you have me thinking. I'll let you knoiw how this turns out.

There is a company called Rodman, and they make carbide drill bits, looks a lot like a hammer drill bit, but are used for drilling tough things like stainless steel.

I have done as Ed stated. Only heat a small area. A cutting torch tip works best for this.

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JTOOL wrote: I was told several years ago that if you heat it red hot and let it cool slowly, then that softens the metal. I've never tried it. I don't know if slowly means let cool back to ambient or put in warm sand or ash. Then after drilling your holes, heat it back up and then quench it in something. Again, I don't know if that means water or oil or super quench. Let us know what you end up doing.

 RED HOT is a very loose term. Really red hot will cook the carbon out so you won't get it hard again. Critical temperature is where it needs to be to harden, and that varies with the type of steel. Quenching can be done with air, water or oil, depending on the type of steel.
 Annealing temperature is lower than the critical temperature, maybe just starting to show a red glow, and cooling should be SLOW.
 After re-hardening, it should be put thru a draw heat, which kinda stress relieves the part and lowers the hardness a bit so it doesn't break like glass.