Date: Fri, 29 Oct 1999 11:23:47 -0700 (PDT)
From: mwest_at_cdsnet_dot_net (Mike West)
To: VintagVW_at_listproc.sjsu_dot_edu
Cc: vintagebus_at_type2_dot_com
Subject: [VB] Hammer Welding (answer)
Message-Id: <199910291823.LAA29621_at_lenti.type2_dot_com>

I have run across the term "hammer welding" several times in the last few 
weeks.  It seems to be associated with welding contoured pieces of metal.  

Can someone point me toward a source of more detailed information about this 
process or at least sketch an outline of it?  I have begun dabbling in the 
worlds of mig and oxy/acetylene welding and am very interested in learning 
what is practical to aspire to once I become comfortable with the basics.

mark fitzsimons


Hammer welding in the sense they are using it is a misnomer . .

It just seems  like hammer welding . . .
What they are doing is controling their shrinkage with a hammer.

First condition: we are butt-welding a section into the outside
of a car . . . on all? vehicles, even "flat" sections have a slight
curve outward . .

This panel you are putting in fits perfect with a .02" (1/2mm) gap
all the way around . . all surfaces of the patch are aligned with 
all the adjacent surfaces of the the "parent" . . .

Now you want to "tack-weld" the patch into it's final resting place.

You do this like lacing up a boot . . one on this side and one directly
opposite on the other side so the tacks pull against each other . .

Now we have to look at the tack-weld itself . .
If you're using a coat hanger for filler metal, it's eqiv. to a 60XX
weld rod . . . if you are using my mickey mouse wire welder, it has a 
E-70XX  . . . there are numbers where those X's are but they vary . .

That 60 and 70 are the tensile strength of the filler material . . 

That reads 60 thousand psi and 70 thousand psi . .

Getting back to the weld itself, lets take a tack 1" (25mm) long with
a 1/8" (3mm) thick . . . this gives a cross-section of .12 sq. inches
times the 70 thou. tensile gives 8400 psi that tack is pulling with.

While I admit to gross over-simpification there, that's a fair look
at what is happening  . . . so this tack just pulled your 
contoured surface flat . . . 

We don't want that, so put a dolly on the back side and whack 
that weld a sharp blow  . . . this thins the weld and expands it in
the plane that relaxes its pull . . .

When you get the whole patch back where it's supposed to be, you make 
another tack on the opposite side and go thru all this again  . .

Now if you aren't too good at this "shrinkage" thing, you will do a 
lot of hammering . .  :-)

Real Hammer welding has been around as long as the forge . .
It's done in a forge / anvil setup . . .

Get the two ends of metal to be welded white hot, lap them 
and hammer the lap into a single thickness again . .
Now lap the metal again, like the seam on your blue-jeans
and hammer it back down to one thickness again . .

Several heatings and treating the faying surface with flux,
were left out of the above for clarity . .  :-)

The Japanese Samuri Swords are a famous example of hammer
welding . . besides being an early example of high-carbon
steel . . .

Some-how none of the above lends itself to slamming a new 
panel in the side of a car-door tho . . .