Guillotine Failure

[Jason L]

A while back, I was given several 24" circular saw blades 1/4" thick. I figured they might be useful to make a small guillotine tool out of so I drew up the plans cut out one side out and all seemed to be going well. I laid out where I wanted holes to be to bolt this thing together and that's when I ran into trouble. I got out the handy center punch and when I hit it, the tip flattened out completely. I redressed the tip and tried again, same thing. Ok, next try I took some spring steel and made a quick and dirty center punch. Flattened it like a pancake. Not even a scratch on the saw blade. I figured if I can't center punch it, I can't drill it so the next attempt will be something a bit easier to work. From the little I could find online, these big saw blades are typically softer steel with hardened teeth. These are hardened through and through. Now I have 8 large saw blades I have to figure out what I make out of lol. There are worse problems to have I suppose. They might make decent chisels, we'll see. 

[Frosty]

Before you give up, give this a try. Cut a short piece of 1/4" or so round stock, chuck it up in your hand drill and round the end of the rod. I just run it on a grinder while the drill is turning. The idea is to make a rounded end that's centered, it doesn't need to be perfect just circular and centered on the rod.

Now place the end of the rod where you want to drill the hole pull the trigger on the hand drill and apply pressure. Don't do a hand stand on it but push, listen to the motor you don't want to strain it but you DO want it working. Keep spinning the rod until the saw steel turns red under the rod and let it air cool.

This will run the hardness out of the steel in a very localized spot IF it's an alloy that can be normalized without special equipment. It doesn't work with all alloys but large circle saw blades shouldn't be anything too exotic.

Now try center punching it with a hardened punch. If it still doesn't want to punch apply the rod again but after it drops below red heat spin the rod to it again but only push hard enough to keep it blue for a couple minutes.

It's an OLD trick my Father was taught by an old timer in the 1930 and he said the old timer said it was as old as dirt.

The blade might have enough nickel in it to make for good pattern welded billets.

Frosty The Lucky.

 

[Irondragon Forge ClayWorks]

My grandfather taught me that trick when I was a puppy. It works like a charm to normalize for drilling hard thinner steel.

[Jason L]

That is an amazing idea! I'd have never thought of it on my own. I had thought about throwing it in the forge and puching the holes but I was afraid it would warp and I really didn't want to get into that mess. Thanks guys!

[BillyBones]

What did you cut it with? I ask becuase drilling is cutting. 

If you are using these pieces for the body of a guillotine i would just anneal the parts. If you can, run your drill about 150 RPM and you should be able to cut it like butter. And that is with a standard HSS drill. If can get a carbide drill you can go upwards of about 800 RPM. Carbide though has no give and i mean none what so ever. Do not use one if all you have is a hand drill. The slightest side movement and the drill will shatter. That is cutting a piece of high carbon with a 1/2" drill at about 1/3"-1/2" a minute. Just keep in mind that when cutting steel, speed is not your freind. I do not know how many people i have seen try and speed up their drill when it wont cut when what you need to do is slow it down. 

There are dozens of speed and feed calculators on line. You just have to plug in your numbers. Diameter of the tool, how deep you want to cut per minute (feed), number of flutes/teeth on the tool, type of material, which tool (HSS or carbide) and it will spit out a range of RPM to cut it at. 

TiN drills are just a HSS drill with a coating to prevent wear, so plug in HSS if that is what you have. 

Any metal can be cut if you use the right speed and feed rate and of course the right tool. 

**disclaimer** this info is off the top of my head. However this is what i do for a living but at my job i have books and charts that i can consult to get exactly what i need. Also as a machinist we do not typically cut hardened steel, it is annealed before we get it and then if it needs hardened we send it out for heat treating.  

[Jason L]

I cut it with an angle grinder with a cutoff disk. It cut with no problem. I haven't tried to drill it simply because it completely flattened the tip of a center punch and a piece of spring steel that i used as a center punch and didn't even scratch it. I'm going to try the localized annealing mentioned above at some point. It's not a priority at the moment but I'll play with it and see what I can do with it.