On Sun, 11 Aug 2013 16:37:38 -0700, wrote:

On Sun, 11 Aug 2013 19:01:05 -0400, wrote:

On Sun, 11 Aug 2013 10:05:35 -0700, wrote:

On Sat, 10 Aug 2013 18:12:15 -0700, wrote:

I bought a small press in a junk shop for $20. I mounted it on a 2x6
and let it collect dust for a year before I started to use it to
flatten sections of copper pipe. It did very well until today: There
was an ominous sound and the frame cracked:

http://www.flickr.com/photos/2768312...7635013299389/

No way will I admit using a cheater bar and even if I did I barely
leaned on it. Anyway...Can this be repaired or is this thing done for?
My understanding of welding cast iron is that it is not a free lunch.

Thanks,

Michael Koblic,
Campbell River, BC
Greetings Michael,
I have experience with this type of repair that worked well. At wotk
someone pounded on the large vise and it broke through the ram that
encloses the screw. I was taking a welding class at the time so I
brought it into class to fix it. I built an open top "oven" out of
firebrick and set the vise part into it. I then heated the veed out
part to nearly red heat with a big torch. Using flux and brazing rod I
wetted the cast iron vee with the brazing rod. Once I had the surfaces
completely wetted I just filled with brazing rod. I did this repair in
about 1.5 hours and used a lot of welding gasses. This repair was done
over 20 years ago and I still use the vise. Frankly, I did the repair
for the experience, your press may not be worth it. It may just crack
somewhere else.
Eric
A similar method, but likely stronger, is to pre-heat as above and
then weld with "ni-rod" (high nickel) or stainless steel wire. Makes
a very strong and permanent repair - the weld and the absorption layer
around it are stronger than the base casting, as the alloy from the
Ni-Rod or stainless "draws out" into the casting. Let it cool slowly
and naturally when finished. I've used this method on numerous
machine (agricultural) and tractor parts over the last several decades
and I'm not aware of any of the repairs failing.
Greetings Clare,
Your method described above will certainly result in a repair that is
stronger than the parent metal. Brazing rod is as strong as or
stronger than the cast iron parent metal. I'm talking tensile
strength. In a wear or impact situation welding with ni-rod is
certainly a better solution. When you say "draws out" I assume you
mean the capillary action where the melting metal penetrates the
casting between the crystals. This also accurs when brazing and silver
soldering and is one of the reasons why silver soldering and brazing
can result in such strong joints. When brazing cast iron I'm not sure
how well the brazing metal penetrates into the casting.
Eric
I've grazed castings too, with mixed results - and silver brazed
things as critical as distributor drive gears. Until we figured out we
needed to use a wooden alignment pin to install the head on the R12
rallye car we broke 3 didtributor drive gears - and there were no more
available locally - so I ground the parts of 2 damaged gears to fit
and silver brazed them together. It stood up for 3 years of
competetive rallye driving and another 3 years of my brother thrashing
it as his every-day whipping boy. It didn't break.

The "drawing out" is more than capilliary action - it is actually
"alloying" the puddle, making a maleable transition from the base
metal to the weldment and back to the base metal which takes the shock
better than the base cast and "absorbs" the shock - preventing the
brittle cast from breaking as easily under shock. Brass doesn't
appear to do this as well. I've ended up grinding out brazed repairs
and redoing them with stainless (tigged) on several parts - and
stainless welding even permanently repairs cracked exhaust manifolds -
which are often high nickel castings to start with and do not last
long when brazed..

Welding with mild steel rod causes a brittle zone on both sides of the
weld, where the carbon has been "drawn" out of the casting, which
makes the part succeptible to breakage under even low levels of shock
(and even vibration in some cases).

Just my experience, going back 45 years and proven as recently as last
year.