Dar Shelton
sheltech@webtv.net

>I have made a startling discovery that I think people should know about. One-inch acrylic spacers can, over time and use, compress, causing the top and bottom surfaces to no longer be parallel. I am not talking about the small dents, dimples and creases in the surface, which can also cause problems, but compression over the whole block that causes one corner or one side to be measurably "thinner" than the other. For most applications, this is not a big deal. But the amount of deformation, as much as 2 mm, which may be doubled when you are using two spacers, is enough to cause blanking dies to fail.
>I discovered this after teaching a workshop. I couldn't figure out why the student's correctly made dies weren't cutting. After determining that the press platens were parallel, I could see that when raising the platen with two spacers in place, there was a noticible "gap" on one side. When I checked my press at home, I found the same problem —which is when I measured the spacers. All of my well-used, at-least-ten-year-old spacers and those at the school were "off" in significant amounts. Then, over the last week a friend was having a serious crisis over having both (professionally made) old dies and then new replacement dies that wouldn't cut. Her 1.5-inch spacer was off by 3mm!
(snip) You should use a clean flat surface for blanking dies anyway because dented or damaged spacers can damage your die.
>Anyway,
>As Gilda Radner used to say, "It's always something!"

So are the friend's dies working now?.
The described failure should NOT cause any damage to a well made, properly heat treated pancake die . The worst that can happen is that the die is prevented from closing  all the way, and this keeps the part from being cut all the way out. Such a die is expected to work fine  after the plates are fixed; if not, then something else has gone wrong with the die.
However, with an unhardened die, I can envision a die getting 'permanently' bent if part of it closes and other parts are prevented from closing. Such dies aren't springy enough to recover from such bending; hardened ones are.      Some unbalanced shapes like to punch out in stages instead of all in one synchronized pop, and sometimes workers (never me, of course (^:#) take out the die before
it's done cutting. Sure enough , part of it is closed, part isn't, and the blank is in limbo. Happens sometimes too when a press lacks power for a certain shape. Now, this
double blaking , when caused by an unbalanced design , can cause the die punch to shift laterally and incur damage from running into itself, but genarally this should not be associated with the situation Susan encountered, and usually the die is fine afterwards. Adjusting the die's position in the press will usually eliminate the problem. Actually, this happened to the giant leaf die, which IS balanced; it happened because the hinge was too long and flexible.  It is, in fact, almost always something.
Dar