[modeleng] Against the grain

  • From: stepney <alan@xxxxxxxxxxxxxxxx>
  • To: modeleng@xxxxxxxxxxxxx
  • Date: Sun, 15 Apr 2012 18:15:29 +0100

We all know that wood has a grain, and most of us will have read that 
metal does too.
However, you can go for a long time without noticing it or it being a 
problem.

I cant remember the last time that the grain in metal caused me any 
trouble, until today.

I needed to do a simple turning job.
What it ended up as was:
a piece of steel, 1" at 1/4" dia, then 3/8" at 0.600 dia, and then 1/2" 
of 1/4" dia.

In one of the "junk" boxes I have some 4" lengths of 3/4" steel (of 
unknown specification) with surface rust, so I decided to use one of them.
Put in chuck and turned down about half the length to get back to a nice 
clean surface.
Then reversed in chuck to do the same from the other end.

The first end had a superb finish, and looked excellent.
However, the other end looked as if it has been chewed away by a rat!
Same tool, same setting, same feed and speed.
I then tried several different feeds etc, but nothing I tried enabled e 
to get a decent finish on the "rough" end.

Ahh well, enough playing about. Reversed in chuck, and turned the 1" and 
3/8" lengths, so they ended up with a decent finish.
Then reversed again and turned the 1/2" length (of 1/4" dia).
Finish lousy, but it didnt matter for that particular section.

Having made the part, I then tried another piece from the same batch, 
and found exactly the same effect.
I assume that it is a heat treated steel, and must have a particularly 
coarse grain structure.

Unusual, and consequently, interesting.

Alan

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