Cogsy
Well-Known Member
I was turning a 1" lump of cast iron bar today, leftover from a bar that I previously turned the liner for my Rupnow engine. It turned fine last time I used it, and the O.D. turned fine but left some strange markings on the surface, kind of a spiral pattern, maybe 1/2" wide for the length of the cut. I did get a photo but it's on my phone and getting it to the computer is difficult. It looks duller than the surrounding metal but the surface finish feels the same.
Anyway, I drilled and bored the piece with no problems and I was thinking how nice cast iron is to machine, then I started on the cooling fins.
The first 3 or 4 were no problem but then I started to get a lot of noise and I had to back out of the cut. The HSS parting blade was worn down on both sides and was smoking hot. Instead of cutting a groove it was cutting a V. I resharpened it and tried again and it finished the cut, but it was noisy. Next groove it did the same thing. Resharpened, tried again and it just kept happening. I changed parting blades and it just kept happening.
I have read about cast iron having a hard skin but I was far deeped into the bar than that. Did I find some sort of hard spot? When I was ready to part the piece off in a different spot, I ran into the same issue yet I manually hacksawed it in the same spot and it was easy.
Any ideas?
Anyway, I drilled and bored the piece with no problems and I was thinking how nice cast iron is to machine, then I started on the cooling fins.
The first 3 or 4 were no problem but then I started to get a lot of noise and I had to back out of the cut. The HSS parting blade was worn down on both sides and was smoking hot. Instead of cutting a groove it was cutting a V. I resharpened it and tried again and it finished the cut, but it was noisy. Next groove it did the same thing. Resharpened, tried again and it just kept happening. I changed parting blades and it just kept happening.
I have read about cast iron having a hard skin but I was far deeped into the bar than that. Did I find some sort of hard spot? When I was ready to part the piece off in a different spot, I ran into the same issue yet I manually hacksawed it in the same spot and it was easy.
Any ideas?