Cast Iron welding Sticks

IMHO the need for pre-heat and slow post weld cooling on simple cast iron repairs is frequently overstated.  It is of course vital on large and stressed repairs but, frankly, I don't think the amateur and inexperienced should get involved with any job that needs pre-heat.  Use it by all means if you are comfortable as it does help to produce a good job quicker but the cold, layering technique I outlined is / was an accepted textbook method for smaller jobs.  When I raised the point with an experienced welder of cast iron he said "You'd certainly do a better job that way but its too slow for a professional like me.".  Meaning of course that carefully putting on thin layers with minimal heat input was well within my limited skills but coping with a hot lump of cast-iron whilst simultaneously getting the right weld bead thicknesses in the right time was not.  He told me that pre-heat was only a small part of a proper job and it wasn't of great value unless you got the rest right too.

I certainly wouldn't bother for "cheese repairs" or fixing chuck collision scars on a top slide and similar jobs.  I recently built up the top slide on my Pratt & Whitney B restoration project and felt that a harder surface to the tool post mount area would be desirable so I used more current and 10 gauge rods.  Worked a treat as the surface is now just too hard to file so I must have got the carbon migration about right.  Largest job I've ever done cold was to stitch an old 15" Harrison apron back together after it had fractured into 4 pieces when it fell over.  Through 2 shaft holes too.  Hard work,  I did have to grind out and re-do a few cracks, but its held up just fine for 10 years now.  Could do better now.

Clive 

hi , cast iron welds need pre heat, plus as mentioned before tap weld area with a small hammer, if you dont have a cool down oven, stick the job into a bag of lime, if you dont have that, use dry cement, Iv'e done welds with a stick welder and use the stitch method of welding, it lessens the stresses, came back next day to get job out of the lime container, and it was still warm, Some welding sticks such as Eutectic are excellent, BUT are expensive, even for a pack of six. but that was some years ago.

John Holloway

PS made a couple of indexable tool holders today, I had to go inside next to air conditioner a few times as the temp even in the insulated workshop was over 32 degrees.