drilling O1

hardheart

hardheart

Joined
Sep 19, 2001
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I hammered out a small blade, about 9" oal, and am not having an easy time drilling holes in the tang. It's O1, and I've stuck it in vermiculite sandwiched in 1" kaowool a couple times, from a bright orange glow in the forge. Thing is, it's hardly warm to the touch after 3 hours. It seemed to grind ok on the 2x42 belt sander, and I was also able to work a little around the plunge with a 6" single cut file.

Are my bits too cheap (they are cheap), does the steel need to stay hotter longer in the vermiculite, or does O1 just not drill easily?
 
O1 is not an easy steel to anneal. You are not getting it nearly as soft as you should for drilling. Without a oven and good temperature control, you will probably get some degree of hardening.

some things that should help. bring the O1 up to 1000 deg or so, and then let it cool again. this is not a annealing, more like a high temperature tempering. Use Cobalt drill bits or a high quality High speed drill bit(I like Norseman bits myself) Run them at a slow speed with plenty of coolant. If you have access to carbide bits and a high speed drill press, use those instead.

Ken
 
thanks, first order will be to get some better bits. Next is probably a controller with capability to ramp temp up/down, not sure what I can do with the vermiculite so I'll explore other avenues.
 
Hot punch it....Frustrating work, and can often spread the material a bit, but it's good, traditional, practice.
 
Here's a trick that mostly works.......

Clamp it down right where you want your hole. Cut the head off a common nail and chuck it up. Use high speed and mash down on the quill. When the spot turns blue, it's as soft as it's going to get. Change to your drill bit, low speed and have at it.
HTH
 
Use a new HSS or Cobalt drill bit, go slow (have the drill press on the slowest setting) and if necessary "Cool Tool" is your friend.
 
Due to the unavoidable formation of chromium and other carbides cooling in vermiculite will msot often lead to heartache when drilling O1 even if there is no bainite or martensite present (which there probably will be). Spheroidizing is the only practical answer if you plan on milling or drilling after forging. Heat it slightly above critical (1375F) and hold before dropping no more than 50F per hour or harden and then heat to 1275F-1300F and hold for an hour before cooling and you may get close to the first method. Either will turn those drill destroying carbide sheets into harmless little spheres in a soft ferrite that will simply move aside and tear out when the drill bit encounters them.
 
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