[TheForge] Welding cast iron

[Bisnette SSgt Bernie R]

In my humble opinion, one of the most forgotten arts that we forget about is
using the spark test to identify what is contained within the metals.  Do
the sparks look like arrows, or fire works, what is the color etc?  Much can
be told by the grinding wheel...especially those of us who scrounge metals
from scrap heaps and junk yards. I've actually tripped into some re-bar that
had rather high carbon content, enough that it heat treated rock hard. Take
the broken piece and run it against a grinding wheel and see if it is
malleable cast.  I think you are sitting on a golden opportunity Aubrey, in
that you have room to experiment.  Grab some nickel rods, preheat that piece
and hit with a tack weld and see what happens.  If it crumbles, you can
always forge one. 

-----Original Message-----
From: Washington, Aubrey O. [mailto:awashington at ou.edu] 
Sent: Thursday, December 08, 2005 12:40 AM
To: theforge at mailman.qth.net
Subject: RE: [TheForge] Welding cast iron

As long as we are talking about welding cast iron, I have a question.
Recently I bought an Acme post drill that looks exactly like one in the 1915
Sears catalog; the one for $7.10 at
http://www.anvilfire.com/21centbs/drilling/postdril.htm.  After cleaning off
90 years of ossified grease and dirt and oiling it up, the drill worked
great!  I was able to drill a 3/4" hole in 1/8" plate in a couple of
minutes.  I was so happy I began gleefully drilling holes in everything I
could find.  Then came the problem; I broke my new toy. 
 
The small wheel at the top advances the down-feed of the spindle by means of
a pivot arm that works against the eccentric hub of the flywheel.  I broke
the pivot arm by continuing to crank after the spindle reached its maximum
extension. In my feeble defense, it broke at or near a previous repair.
 
Now here are my questions.  Is this arm likely to be cast iron?  It looks
like it might be because the angular shape of it looks like it was designed
to release from a mold.  The interior of the break looks grey and grainy.
>From this thread I take it the repair could be done by arc welding with
nickel rod, brazing, or gas welding with iron.  Bernie points out that
expansion is often a big problem in welding cast.  But that should not be
much of an issue with this part since it is small and there is no
restriction on expansion in the length of the arm.  It would also be easy to
pre and post heat.  BTW, if I decide to weld it, I will find someone else to
do it since I'm a lousy welder.
 
Is any repair likely to be strong enough for the strain put on this part?
Would I be better off just forging a new arm out of mild or medium carbon
steel?
 
Aubrey Washington
Saltfork Craftsmen ABA, ABANA
Rock Creek Forge
Norman, OK