[TheForge] Advice? Air hammer die and anvil fit-up

[theforge@mailman.qth.net]

Cast Iron has great strength in compression, but has relativley poor 
strength in tension or shear ( the reason so many dovetails are broken 
off power hammers, andf edges chipped off of cast iron anvils).   I 
would make sure the dies make solid contact with the base, otherwise you 
could be asking for advice for a much more complicated fix  in the 
coming months.

As far as lowering it, the traditional method would be a cape chisel to 
create grooves, followed by cold chisel, followed by files.   I have 
done this before ( making a horn for my first fabtricated anvil) and it 
really is faster than it sounds.   M.T. Richardson's Practical 
Blacksmithing quotes a reasonable repeatable days work with a chisel to 
be a 3/4 " wide, 1/16 " deep groove  600" inches long in cast iron.   In 
other words, 50 foot long groove.  I haven't matched that yet, but he 
didn't state the length of a day.   If you assunme twelve hours (circa 
1890), then that would be a little better than  four foot an hour.  

Personally, for what you have left, I would use a 16 inch nicholson 
double cut file.  It removes metal almost as fast as a grinder and is 
easier to produce a flat surface if it is handled and proper technique 
used .   Last year I was finishing something up in the dark with a big 
file and had a friend holding a flashlight for me.  In the beam of the 
light you could see the particles of metal coming off.  The volume was 
really amazing.  I find myself reaching for it lot more often than the 
angle grinder.  It has  less noise, better control and no sparks or 
embers flying into every ship recess.  Best of all for me, no bits of 
fiberglass reinforcing adhering to my sweaty arms. 

Charles



Mike Spencer wrote:

>I'd like to have suggestions about how to deal with setting up the die
>and anvil on my 300# air hammer.  At the risk of being long-winded,
>I'll explain the situation.
>
>This is a hammer with a separate, ca. 2.5 ton cast iron anvil that is
>already in place.  Previous owners of the hammer ran it with a loose
>die, wedges it with crude chunks of torched off scrap and, at one
>point, tried to weld the steel die to the cast iron anvil.  The anvil
>was a mess.  Worn, beat up, out of square, swales in both the surface
>and the floor of the dovetail, not to mention puckers and pits all
>around from the failed weld attempt.  The crappy wedges were welded in
>place.
>
>I have it ground down to pretty flat -- within +/- 1/32 -- and
>perpendicular to the tup bore.  But now the floor of the dovetail is
>ca. 1/16" lower than the anvil surface.  The die, which weighs maybe
>140#, now hangs on the anvil surface but there's ca. 1/16" of space
>between it and the floor of the dovetail in the anvil.
>
>    Would it be reasonable to put a piece of 16ga. sheet under it and
>    expect the die to bed itself into the steel?
>
>    Is it really neccessary to grind another 1/16" off the anvil
>    surface?
>
>    If I did that, would it fast and (relatively) easy to use a
>    hand-held belt sander and, say, a 40 grit Norzon belt to hog off a
>    16th?
>
>It's real slow and tedious to get an even, approximately flat surface
>with a angle grinder using an abrasive disk and a cup wheel and a jury
>rigged gauge hung from the bore.
>
>I think if I *did* grind it down to an eyeball fit, I could get it
>even better by lapping it in.  I have the worm gear drive from an
>automatic coal stoker that outputs about 6 rpm when driven with a a 3450
>motor.  I was thinking of making a little crank and con-rod, mounting
>the rig next to the anvil and connecting the con-rod to the die.  I
>could slather it with coarse lapping compound, then go off and leave
>it run for half a day and the die would be ground back and forth on
>the abrasive maybe 2" in each direction (just under its own weight).
>The steel die is pitted but pretty flat and true.
>
>On the other hand, if I stuck some 16 ga. sheet under the die, I
>couldn't very well do that.
>
>The goal here is not to spend too very much money and time getting
>this thing together utill I find out if it's going to work.  On the
>other hand,  I don't want to leave bits unfinished that will
>neccessitate taking the thing apart again later to get it right.
>
>Mutter, mumble.  Any suggestions, coments or pointers  welcome.
>
>
>- Mike
>
>  
>