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[Orchid] Pancake dies
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Dar Shelton Sunday, July 17, 2011
   
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    I'm writing this for two reasons, in whatever mixture of motivations
    it seems like; one is to present accurate information about pancake
    dies and the other is to promote myself, because I make pancake dies
    and that's been my profession for 24 years, so it's safe to say I
    have accurate information. Apparently not everyone who needs to does
    though, and this bothers me, because it's about people out there not
    fully understanding the capabilities of the process, not knowing the
    extent and effectiveness of it's applications. I'm not into an
    adversarial, me-versus-him approach, so I will just call the other
    pancake dies (that I know of) that people can buy "laser-cut dies",
    and for the purposes of this particular post I'll call the dies I
    make "angled dies","hardened dies", "angled, hardened dies", or
    maybe "sawn dies ". These terms describe the difference in how the
    types of dies are made, and that has everything to do with how they
    perform. 

    I will have to start at the beginning because the most basic thing
    about properly made pancake dies is that the cut that creates the
    cutting parts of the die are made at an angle that is NOT
    perpendicular to the surface of the die plate. Since lasers are not
    able to cut cleanly or accurately enough unless they ARE
    perpendicular to the steel die surface, these dies (obviously) have
    cutting parts that are not made at an angle.This difference is
    critical, and the easy analogy of a pair of scissors will
    demonstrate why. 

    Effectively, cutting a die at a specific angle, depending on steel
    thickness and sawblade size, creates a zero tolerance fit between
    the cutting components of the die, very much like a pair of scissors
    that's snugly fitted , where the blades slide along in contact with
    each other, no gap between them for any material to pull in and get
    stuck, or cut sloppy, or not cut at all. Laser-cut dies do have a
    significant gap between the cutting edges, and from the analogy, and
    everyone's experience with scissors, it's easy to understand why this
    gap has the potential for causing lots of problems. 

    Having a gap isn't always a problem, and using hard steel isn't
    always necessary, so the laser-cut dies are useful to some extent,
    and work on thicker material as advertized, but there's something
    about cutting pancake dies without the angle that is contrary to the
    fundamental concept of pancake dies, in my way of thinking. This
    isn't an abstract idea either, because it's deeply rooted in
    experience : the problems caused by loose t= olerance (the gap
    between the cutting edges) far outnumber problems caused by any other
    issue, and when you're in the business of making tools that work and
    cutting parts that people are happy with, you'd better figure out
    how to make dies that you don't have problems with. Which is the
    first thing I started working on back in 1986 when I got the "RT
    Blanking System". Instructional material available at the time was
    vague and rudimentary but I became obsessed, and one of the first
    problems that jumped out was that the table of angles given resulted
    in loose dies that either left burrs on the backs of parts, and at
    worst, allowed metal to bend, get pulled into the die, and jam itself
    in there. It doesn't take much of a gap in some situations to begin
    to cause these problems, so the way I approachit, there is very
    little room for deviation when setting the angle of cutting. When
    working with metals thinner than 22 ga. (generally speaking) the dies
    simply need to be tight, sometimes so tight that they need to be
    opened with some force. 

    I just recieved two relatively new dies back in the mail that
    malfunctioned. I can feel the cutting edges click as they contact
    each other as I open and close the empty die, which I can do freely;
    this means that the die is relatively tight. Extra-tight dies are
    harder to open, and loose dies don't contact at all, so this die is
    medium tight, but it (both did) jammed while cutting 24 ga.
    patterned brass. These are dies that are made with every effort to
    perfom well, not performing well because of this one main issue,
    cutting angle and tightness. In reality, another thing is often
    involved, which is that if metal is loaded too close to the egde of
    the design on a die that's just a hair loose, that invites the metal
    to pull into the die and jam it, while loading with more excess
    material bordering the design can prevent that from happening. That,
    as opposed to a die that's very tight, where you can literally load
    on the very edge of the design and have sharp, feathery pieces of
    scrap leftover, and a part that's still clean as a whistle. I'm
    talking about very slight differences in cutting angle, maybe 1/2 to
    1-1/2 degrees, which result in tolerance differences of fractions of
    thousandths of an inch, up to maybe a couple thou.. Another very bad
    thing that can happen when a die jams is that it usually jams on one
    side (left or right, not front or back) and forces the whole punch
    part of the die over to the other side. This can cause the cutting
    edges to overlap on that side, and when the die closes in this
    position, the cutting edges have nowhere to go but to crash through
    each other and damage that area of the die. This is almost always
    catastrophic in that the die will never cut cleanly again, and often
    never cut again without jamming. The problem with trying to sharpen
    cutting edges in this situation is that you'd be removing metal from
    exactly where you need to have more metal, and this (adding metal)
    is of course impossible to do. Not quite entirely impossible, as dies
    can sometimes be peened to stretch the steel and force a little bit
    into the gap, effectively tightening the die up. Sharpening is
    counterproductive and is not advisable at all. 

    Again, I'm talking about small amounts of looseness in dies
    potentially causing big problems, so a gap of maybe .005" or .008" or
    whatever, left by a laser cutting perpendicular to the steel, is
    completely unacceptable to my approach to making pancake dies.
    People using the dies and having any of these problems ought to know
    exactly why they are occuring, and know that the process itself is
    not to blame, that clean parts in thick or thin material are not
    hard to make when the dies are made a certain way. Also, that
    designs are not limited to basic, simple shapes. Using tool steel,
    and hardening it after the dies are sawn, opens the door wide for
    cutting more intricate shapes. It's not that much of a stretch to
    say that anything you can saw, you can saw as a pancake die if it's
    sawn and heat treated properly. The other huge advantage to heat
    treated, tool steel dies is longevity, but that's a whole other
    barrel of monkeys. I really wanted this post to beabout angle and
    tightness, so, class dismissed. 

Dar Shelton

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