home built cutter, steel type?

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LEEQ

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So I'm contemplating making single tooth cutters for gear cutting on the mill. The toughest material they will probably be cutting is mild steel. I will be doing a caveman heat treat job. Like heat to straw yellow then quench in oil. No fancy equipment. They take the form of 1/4" square bar. I am getting a bit overwhelmed in the selection of steel for the cutters. I found a listing of tool steel that included 1018. The same outfit had 1018 bar stock listed in cold formed at a considerable savings. Are they different end products despite being the same alloy? Is either one suitable for a cutter shaped like the space between teeth and spun around impacting and cutting steel once per revolution? I'm new to tool type steel and need some help. What should I be looking for?
 
1018 would be a poor choice. It doesn't harden well or much. For your oil quench you would use O-1 which is commonly drill rod. Any reason you couldn't use a high speed steel bit that is already hardened? Just grind it, insert it and go to work.

Dave
 
Lathe bits ground sound like much less trouble, I'm not sure how I would duplicate this by grinding though. Not in my limited shop. I plan on reaching the proper geometry with some math and certain sized end mill to achieve certain radius at a certain place on the bit. I know this works, so I'm not changing the bit design. I might be able to anneal some old drill bits and use those.
 
We use to use a lathe bit as a single (fly) cutter for gear teeth all the time it is slower but works well. Ray
 
Did you grind the profile?
 
O1 drill rod (and you can get it in flat as well.)

Relatively cheap, readily available, and easy to work with. Hardening and tempering it is harder to describe than to do. Quench it in oil and toss it in the easy bake oven for a while to temper. It is pretty forgiving. Another approach is hobbing gears (assuming that they are spur gears but you can also hobb worm gears) Hobbynut had a series on making them on youtube and Jose Rodriguez has a video that you can buy through LMS.

The real advantage to using O1 over HSS is that in it's annealed state, it is much easier to work. Just patience and files and you can make whatever shape you want.
 
At this point I don't want to hob just yet. I will get some 01 or similar tool steel if I have to, but I'm not finding much in the way of decent prices on 3/16" or 1/4" square. Do you guys know what regular old drill bits are made of? I'm pretty sure I can find free old bits and anneal them in the coals of a wood fire. I would have to figure their steel type so I could find the proper heat treatment though. Could you tell me how you did that grind job? Any pics or description would be great. I might take that 1018 1/4" square and piddle. I just have a 6" grinder with fairly fine wheels. One advantage of the method I had in mind, would be repeatability. I could sharpen both ends of a few bits while I was set up and know I cold swap out midway through a 47 tooth gear if I found myself in need. I don't know about my ability to freehand two bits the same.
 
LEEQ said:
At this point I don't want to hob just yet. I will get some 01 or similar tool steel if I have to, but I'm not finding much in the way of decent prices on 3/16" or 1/4" square. Do you guys know what regular old drill bits are made of? I'm pretty sure I can find free old bits and anneal them in the coals of a wood fire. I would have to figure their steel type so I could find the proper heat treatment though. Could you tell me how you did that grind job? Any pics or description would be great. I might take that 1018 1/4" square and piddle. I just have a 6" grinder with fairly fine wheels. One advantage of the method I had in mind, would be repeatability. I could sharpen both ends of a few bits while I was set up and know I cold swap out midway through a 47 tooth gear if I found myself in need. I don't know about my ability to freehand two bits the same.
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I think your over thinking this we hand ground a lathe bit to fit the gear we where making, if we where starting from scratch we would find a gear with the same tooth and hand grind the tool bit on a bench grinder to fit that gear. Most of the time we would grind two or three in case of a crash but a regular lathe bit is good enough I would look no further than that. Just take your time and grind it till it fits the space inbetween the gear teeth just like you would when cutting theads. It really is not any differant than sharpening a tool bit to cut an ACME thread.. Ray
 
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