I think Ill need to clarify what drop hammers were developed for.
so first a bit of history.
The birmingham jewellery quarter grew in the late 1800’s on the back
of the riches created by the wealth of the British empire. By then it
was already mechanised for production runs of many hundreds of
identical products as follows.
In the absence of hydraulics, all processes of delivering energy
were mechanical.
so for the initial blanking out of shapes, hand operated screw
presses called fly presses were used with what is called open tooling
this was a punch in half hard steel screwed up into the sliding part
of the press which registered in a die held down on the press base in
a bloster.
these presses were accurate to the point where the punch would
consistently align itself accurately over many hundreds of blanks.
The dies were always made from crucible steel fire welded to a
wrought iron base usually an inch thick. this was hardened hard.
so when the punch became blunt, one removed it hammered it to swell
it and broached it through the die.
These presses were also used for bending doming folding upsetting
edges. almost no limitation to what tooling one could put in them.
The best maker was Sweeny Blocksidge, and I have several of these.
Beautifully made and precise to 1000th in.
They range from 1 ton rating to 10 tons. however they would not nor
were used for the next much more energy intensive forming. this is
where the drop hammer came in.
Basically this is a cast iron weight ranging from 50 lbs to 250lbs
sliding between guides also of cast iron, set up abve a cast iron
base usually 10 times the hammer weight also in cast iron, builtonto
a very hard base of cement and stone.
the lift mechanism was a sisal or hemp rope over the top of a cast
iron flanged lift wheel some 2ft in diameter driven by the line
shafting it was fixed to.
the operator was in a trench in front of the base so the working
height was at waist level.
He pulled the rope down onto the lift wheel which by friction lifted
the hammer to what height he needed to do the work.
he let the hammer fall and caught it on the rebound with the rope
and set it in the parking position with the safety catch. Then changed
the work piece for a fresh one. Made mainly by Hazelwood and Dent.
The hammer usually had a flat hardened face insert for one sided
work with the die in concave reverse relief held down on to the base
with 4 very large screws set parrallel to the base face.
these dies were also made from crucible steel fire welded to wrought
iron and carved by hand by deaf and dumb workers.
For a 1 in dia button die the face was 2in across by 3.5 in high by
3in dia at the base.
I have a lovely collection of these victorian dies all still
useable. Drop hammers range in energy from 10tons up to 100 tons.
for double sided work like coining, the hammer also has a relief die
set up into it.
then it starts to get really tricky.
Alignment becomes crucial to achieve precise results.
It can be done and once set up wil give many thousands of clear
strikes. the Quarter had many hundreds of these set up and still has,
doing work the simplest of ways over 100 yrs since installation.
I have 3 of these H & D drop hammers, the middle weight one takes
different hamers from 80 lbs to 275lbs which does virtually all the
jobs that come to me.
My needs are somwhat different to a factory installed hammer. As
mentioned in a previous post I wanted to make them transportable so
I could take them to an event to mint at the event FOR the event. so
my build of this piece of equipment had different terms of reference.
Thats another story.
The dies I and clients comission are made from the best Swedish
Grane tool steel, cut on a Dekel 3 d engraving machine hardened under
Vacumn and are of superb quality.
the 1st one I comissioned has done 20,000 impressions and is as
sharp as it was when new.
As for making my blanks prior to minting, I now use power crank
presses ranging from 6 tons to 25 tons.
the dies for these are the same as the fly press dies. there
interchangeable. I dont use any pancake dies. Preferring the
traditional punch and die setup.
I had the opportunity to use the dies of Paul Vincze, a scuptor and
medallist.
to use these I needed to up the tonnage from 100 to 250. I hunted
down a hydraulic press in Birmingham and brought it back to my
workshops. Does a great job.
however for mass production of coinage then were talking 500 tons,
100 a minute auto feed. Not in the art medal world at all.
Best product run was a 40th anniversary plaque of 2500. hot struck
in bronze. Nicest run was 500 fine silver coins, Biggest run was 12,000
pewter coins.
Most satisfying was a button die for a charitable cause. Everyone
involved did it for free.
so what do I make? my CV lists most of the work over a 10 yr time
frame. A lot has happened since then. Tho next year plans are afoot
to mint some lovely designs by a Danish Sculptor. Just love making
things!!
Ted.