Solving a mysterious boring problem


Active User
H-M Supporter - Silver Member
Dec 24, 2013
Hi. I was having a tough time boring a hole in a toolpost that was made from a tractor part. I think it was the pin and plate that connects to the stabilizing foot. Anyway, I found a junk one in the street. It was kind of hard, but I was using what looked like a brazed carbide boring bar, perhaps homemade. It came in a box of tools that the seller gave me with the lathe. There were a lot of mystery tools, including tools that probably weren't intended for the lathe. The lathe came without a chuck, toolpost or change gears. But it did come with all kind of strange mandrels, some bent, and lots of boring bars. This boring bar worked fine on a big chunk of mild steel, or more precisely hot rolled structural steel. But it had a strange problem with this tractor pin. It would cut a little bit, then deflect out of the cut and just rub. I took a good look at the cutting edge and it was worn off. Hmmm, strange. This shouldn't happen to carbide. So, I got out the green wheel and gave it a touch. Imagine my surprise when it sparked as A-2. I sharpened it on an aluminum oxide wheel, and it had the same cutting performance. Just a little cutting, then it deflected out of the cut and dulled and rubbed. Stubbornly, I just kept resharpening it until there was no more clearance to the shank. At this point, it is not worth continuing, since there is very little gain for a lot of grinding. A closer look at the end revealed a rough forged end which kind of looked like a brazed carbide. It just requires so much skill to use A-2 or carbon steel to cut hard alloys. One twitch and the tool is toast. HSS is just so much more forgiving.. If it gets a bit hot, it can just be resharpened, and still finish the job. This simple tool steel stuff is just too antiquated and difficult for my limited skill and patience. I guess I will just cut off the steel and reforge it into a punch or hot cutting tool. A-2 is just great for this use. This was a double mystery adventure: mystery tool and mystery steel. I finished the job wigh a good known HSS tool that I paid $5 for and it was so routine and straightforward.

So, if you are learning, try to take as many variables out of the process as possible so that you are making progress instead of solving mysteries.
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