Cast iron ate my drill

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Rwilliams
Posts: 866
Joined: Thu Dec 22, 2005 2:45 pm
Location: Central California

Re: Cast iron ate my drill

Post by Rwilliams » Wed Feb 07, 2018 12:20 pm

Just completed machine work on a 20 year old Winton Brown stack casting and base casting. The base casting machined real well with no problems. The stack casting looked to be of a different variety of cast iron and had some suspicious appearing surface imperfections as if the metal was a bit on the cold side when poured at the foundry.

I did some clean up grinding on the stack to make it ready for turning in the lathe. Once in the lathe, the base of the stack casting soon became problematic by eating HSS tooling. I converted to carbide insert tooling which also seemed to bounce and slide over the hard spot. Before each pass with the lathe tool, I made a pass with a small stone in the Dremel tool. Worse was the hard spot never did go away, it only seemed to change in shape as the cuts went deeper. Ended up with a slight low spot that will never be seen when the stack is fitted into the base.

Later I was cleaning up the top rim of the stack casting and ran into another hard spot. This time I just used a bigger stone in an air powered die grinder and soon made quick work of the problematic casting. Sometimes a bit of careful work with hand grinders can have our rock hard castings looking just fine without the damage to precision cutting tools.

Soot n' Cinders
Posts: 675
Joined: Wed Jun 27, 2012 5:24 pm
Location: Marietta, Georgia

Re: Cast iron ate my drill

Post by Soot n' Cinders » Wed Feb 07, 2018 4:12 pm

Its looking like Im done with the hard iron on the shay, knock on wood. Got the 6 holes for the door dogs drilled and tapped, and only broke one tap! Luckily was able to get the end out with a pair of pliers.
Doing the file test on the firebox door and ring, looks like they are softer than the smokebox. The file bit in pretty good, even with the skin, whereas the same file wants to slide on the smokebox ring
-Tristan

Projects
-2.5" scale Class A 20 Ton Shay

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