"Bob La Londe" wrote in message
news
"Steve Walker" wrote in message
...

On 7/21/2017 5:58 PM, Bob La Londe wrote:
http://tacklemaker.info/index.php?ac...sa=view;pic=31
You shouldn't need to be logged on to see the image.

This is a pretty typical lead casting (sinkers, jigs, spinnerbaits,
etc)
mold. The hinge shown works pretty darn well. It moves easily,
and
does a good job of helping to hold the mold halves in alignment at
the
hinge end. The opening (handle side) end has two alignment pins
with
radius ends that mate the plates at that end. Over all my
customers are
atleast acceptably happy with it. However to make a mold like this
that
finishes as to 1/2 inch (apx) plates with a hinge I start out by
throwing away a third of the raw material. Basically I start with
3/4
inch flat bar and remove 1/4 inch to leave the 1/4" hinge bosses.
It
just irks me to throw away 33% of the raw material on every one of
these
molds.

No. Bolting a flat metal hinge to the ends is NOT a better way.
It
simply will not hold up over time, and even if its handled with kid
gloves the heat cycling will cause it to work loose. I've seen
molds
made by other mold makers with tacked on hinges, and they get
pretty
beat up and very sloppy over time. It often results in damage to
the
mold itself. Especially if cores, pins, and other inserts or
materials
need to be placed in the mold before casting. These one piece boss
pinned hinges last through thousands of heat cycles. I've done
larger
molds this same way that customers have told me they have literally
run
tons of lead through. It would also require another setup to drill
and
tap to tack on a sheet metal hinge.

Casting a billet with preformed mold bosses is not a great answer
either. The aluminum that results is more porous with the type of
foundry I could setup, and my quantity is to small to have them
forged
cost efficiently. I think it might also drive up the per unit cost
too
much unless I could cast or forge them in great quantities. On top
of
that castings or forgings then have other machining that needs to
be
done to make them useable. One mold company sells cast "blanks,
but I
absolutely hate to work with them because the metal doesn't machine
as
nicely and the surfaces are more of a pain to square up and also
keep
the hinges squared up with both haves coming out aligned.

I did think of maybe using a third piece between the two plates
with 4
pins instead of the two I use now, but then it would not help as
much
with mold alignment. It would also be slower and more cludgy for
the
customer to use the mold. Every idea I come up with is also more
manual
work, or more secondary setup work.

Maybe they way I am doing it is the best way to get a decent result
within my work constraints, but I can't help but wonder if there
isn't a
better way.

Tangent:
If anybody is curious. No I do not use a round over mill to get
the
hinge bosses. I tried that in the past and I was not happy with it
at
all. I cnc mill a radius on the boss with a .001 depth of cut and
then
sand smooth when it comes off the mold. It would be faster to use
a
round over mill, but because of the lead on the cutting flutes and
lack
of consistency from one to the next it would waste part of the
useable
surface of the mold plates. Make larger mold blanks to make up for
it
then means slightly higher (few cents per unit atleast) material
cost
and higher machine time clearing the face of the blank. It works
out to
be a wash on that for cost and produces a CNC cutting the radius
gives
better result in my opinion.





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Build the hinge separately, then dowel and bolt it to the ends of
the
mold halves.

***********
Thanks for the suggestion.

One-piece dowel plus bolt:
http://www.palmerbolt.com/product/14...tripper-bolts/