So there I was, parting about 20mm off the front of an 2MT blank arbor to make a spindle backstop so that I could part some lengths of bar to a standard length (to make four motor mount pillars). I was enjoying the brute grunt of my recent 1hp 3-phase conversion which, when coupled to a carbide insert parting tool, allowed me to run the job at 2,000rpm. The motor had the torque, the tool could take the heat and provided I kept a steady pressure on the cross slide it cut cleanly with no chattering. I'd drilled a small hole in the waste metal and had a 4mm pin in the tailstock to catch the end when it parted through.
The swarf was coming off in a steady stream of blued steel, and as the cut progressed I watched the waste metal go through straw, yellow and purple before settling on a nice deep blue colour. It was remarkably even, but I knew it was telling me the metal was a tad on the warm side.
The parting completed and the waste slug slowed to a stop on the 4mm pin, so I backed out the tailstock and used a pair of pliers to transfer the hot lump to the boring table while I tidied up the edges of my new backstop with an artistic-looking chamfer. 4 or 5 minutes later I'd finished, and was tidying up, I picked up the slug with an ungloved hand and immediately learned that a piece of steel about 30mm in diameter and 20mm long takes longer than 4-5 minutes to cool from >500degC to a handlable temperature even when sat of a big chunk of cast-iron heat sink. Fortunately I had been soldering on the other bench and so there was a wet soldering iron sponge to quench my thumb and forefinger. That was two weeks ago, and the skin has healed but is still smooth - I still have to use the other hand to operate the fingerprint ID that unlocks my phone.
Every day is a school day...
AS
