[TheForge] Repair job

[paul]

> I have been asked to repair a pair of antique boot scrapers that an idiot contractor damaged in a sill replacement job.  1719 house with the matched pair nicely leaded into the granite front step.  In replacing the sill, idiot (or worse) contractor cut the boot scrapers off (not quite flush) rather than move the step.  I need to remove the nubs, reweld them to the scrapers and reinstall.  Anyone have any experience with R&R of lead-mounted iron in stone?  I have thought of three ways to do the extraction of the remaining nubs:  (1) vise grips and slide hammer (preferred), (2) stud extractor and slide hammer ( would rather avoid drilling out the original nubs); (3) heat (prefer not to destroy the original lead or risk cracking the stone: they are 3 inches from the edge.
> 
> Also, the weld itself seems tricky.   I am inclined to use gas to reattach the nubs:  They must be butt welded and SOLID to retain shape and structural integrity.  Forge weld seems dicey considering the weld is at the point that gets nearly all the stress in use.  Is pure iron filler rod avaialble, or am I ok with ordinary mild steel rod?  One of the scrolls needs to be replaced, but I am ok with a forge weld for that, since its a faggot weld along about a 3" surface.
> 
> Any advice  welcomed.  I can post pics if there is interest in this project.
> 
> Kezia

Kind of sounds like the original was installed with lead wool, which is 
still available btw, sort of like steel wool but 'coarser'. The 
advantage at the time was, of course, that it was installed cold and 
'caulked' around the metal with flat nosed chisels. No heat no problem.

see
http://www.acehardware.com/sm-alpha-metals-lead-wool-alpha-metals-lead-wool-price-18--pi-1290612.html
http://www.santarosalead.com/lead_ingots_wool_waterproofing.htm
http://www.answers.com/topic/lead-wool?cat=technology
http://www.gravitaindia.com/leadwool.html
more than you ever wanted to know about lead wool, but you are 
encouraged to hit it COLD...

The safe way to remove the lead would be to drill many small holes 
around the perimeter of the stubs, say 1/4" diameter or so, until the 
stock could be pulled out.  We still use the drilling method to 
dis-assemble cast iron pipe where open flame would be un-friendly to the 
existing structure.
You probably should use the lead wool to remain true to the original, 
but there are many epoxy or polyester anchoring products that would be 
excellent except for their lack of historical accuracy. You would still 
be able to tell if lead wool was used even after you pull out most of 
the lead by picking or drilling, as it will retain its string-like 
structure even after it was caulked (compacted). Even if they used 
strips of lead instead of the lead wool, the wool would be a lot easier 
than cutting up sheet lead to make the strips...which would be easy but 
boring.
Lead melts around 620* and 63-37 solder melts about 350*
see
http://www.efunda.com/materials/solders/tin_lead.cfm

Solders are much harder (less ductile) than pure lead, and since both 
metals shrink upon cooling, which is why we caulk them,  the solder, 
which might look like a good lower temperature alternative to the higher 
melting point lead, is harder to caulk, and might require enough force 
to risk breaking the granite.
sorry about all the commas, it's late for me today...
-- 
Paul Sperbeck
WB9HCO
jadap

  "The difference between genius and stupidity is that
genius has its limits." -Albert Einstein
"Life is hard...it's harder if you're stupid" John Wayne - Sands of Iwo Jima