This is the follow up to the initial post about adding thickness
capacity to a pancake die by adding an underplate made of aluminum.
While the conceptis sound, and fairly routine technically, the
actual time required to make one correctly is prohibitive in most
situations.
Where it could be of sufficient benefit to warrant the extra time
would be with dies that are needed to cut very-thick metal, and a
large percentage of that thickness would be facilitated by the
underplate, in comparison to the thickness of the actual tool steel
cutting-die plate. In other words, it doesn’t make much sense to
make a thin die and only add a little thickness with the underplate,
as I did in my experimental die, which was in 5/64" steel, to which
I added a 1/16" underplate.
The pancake die does need to be at least 1/16" thick, to accomodate
the flat head, socket head screws that are to be recessed flush into
the die, that attach it to the underplate. Those screws would be size
2-56 minimum, for the 1/16" tool steel, and also for the 5/64"
steel. I used size 4-40 in my 5/64" steel, but I also had to grind
the heads down after assembly because the steel was not quite thick
enough for that screw head size. 3/32" steel is the minimum
thickness for size 4-40 flathead screws to be properly countersunk
into. The best tool for drilling the countersink holes is called a
“drill and countersink combo”.
Where this technique would be most useful is when the thickness of
the underplate translates to large amounts of time saved in cutting
a thinner steel for the die and a thicker aluminum underplate, which
also translates to money saved in the cost of thinner steel as
opposed to a steel that’s as thick as the die-plus-underplate stack.
I’m thinking of a 3/32" thick die and a 1/8" underplate, for
example, to be able to cut around a 5ga stock, or maybe 4-4.5mm
thick.
Understand that there are no studies along these lines and that any
tests anyone does are in virgin territory, so you’re on your own. My
common sense tells me that trying this with a 3/64" die and a 1/4"
underplate, to try and cut 4ga white gold is a very bad idea,
because that material would certainly destroy such an insubstantial
pancake die, but I have not formulated any real guidelines for what
might be good and bad specs to start with. My experience is enough
to guide me at least as far as parameters that I would expect to
work, but it’s virgin territory for me as well. I would expect that
a stack of 5/64" steel and 3/32" aluminum to work well, or 1/8"
steel and 1/8" aluminum, or 1/8" steel and 1/4" aluminum, as an
extreme scenario.
One more advantage to this approach is that as you go thicker, by
keeping the thickness of the actual blanking die down, you avoid the
need for longer and longer hinges on the die, which saves money and
time, significant weight, and possibly the need for a very-large
kiln to heat treat the die.
The step-by-step pocedure for making an underplate to match the
cutting die is not conceptually difficult, and as I mentioned in the
original post, is almost exactly the same as what I use for making
and attaching plastic plates to blanking dies that are for trimming
puffed parts that have been formed in matrix forming dies. Briefly,
it goes as follows:
-drill holes into cutting die with bit sized for threading of
underplate
- countersink die plate and drill those same holes for screw
clearance
-make blanking die, heat treat, and finish.
-make template for underplate by vise-gripping a thin plate into the
blanking die as if you were going to cut a part. this plate is sized
exactly to the upper portion of the die, and can extend below the
cutting area (this isgood for the underplate procedure but if you
drill screw holes below the design, it makes for more steps (you’ll
see))
- making absolutely sure that the template plate dies not slip one
tiny hair (or all is lost) use the clearance drill bit to drill
holes through the template plate, filing away resulting burrs
immediately after
-carefully remove vise grips, and not allowing the template to slip
(or all is really lost), blank out the template plate. you now have
what will beused as a transfer plate to position the attachment
holes and design hole onto the underplate
- vise grip this transfer plate/template to your sized underplate,
and use the clearance hole to MARK the attachment holes, do this by
drilling a very shallow conical depression that’s used to locate the
next drill
-while still carefully keeping anything from sliding out of position
(the best way to do all these vise-grip steps is with 3 pairs, and
to always have 2 grips holding things securely; place the 3rd pair
strategically while you undo one, and cycle them that way. (this is
more of a general approach to match -drilling sets of parts, and I
usually only use one grip on these transfer steps)) scribe the
design shape onto the underplate by tracing around the inside of the
design hole that you just blanked from the template
- undo the plates, then use the correct size drill to pre-drill the
holes in the underplate for threading, then thread the holes
-saw the design hole out of the underplate, making sure to saw a
hair outside the scribed line, to allow clearance for the punched
part to fall freely through the underplate
-now the underplate is ready to be screwed to the blanking die, and
that’s that.
the same procedure is used for blanikng dies with protective blocks
attached, as mentioned above. the difference is that, for those, I
use pins and spray adhesive , instead of screws. I generally use
a .060" drill and 1/16" welding rod as pins.
Dar Shelton
Sheltech