Back when I owned Meteor and Cutting Edge, I did a LOT of scratch building. It’s amazing how often we needed to use styrene disks of all sizes and thicknesses.
While you may not constantly scratch build yourself, here’s a simple little trick to ensure you get perfect circles every time. If you’ve ever used any of the punch sets out there you’ve probably already experienced off-round, ragged-edged, or otherwise damaged or imperfect disks.
Frankly, I don’t know whether this little trick is well known or not, but I’ve used it for the last 20 years—-ever since I started having the problems mentioned above. The tool was super simple to make and completely solves these problems.
I’m sure you realize the photo at the top of this article is a joke—-probably not a great idea to use a sledgehammer (even a small one!) for this fairly delicate work . . . Here’s a pic of some fairly standard tools used for punching small disks out of sheet styrene. These punch and die sets are really old; a couple are Waldron sets and the more substantial set was sold forever ago by Reheat Models.
Two problems crop up fairly frequently when punching out disks. First is the “squashing” that occurs when the hammer strikes the metal punch too hard, driving the plastic disk down into the surface below, squashing it. Sometimes it even “dishes out” the disk into a bowl shape. This is great if you need a tiny bowl, but if you’re after a plain disk you have to keep after it until it comes out right.
Although my camera seems to be having difficulty with extremely close focus the two pics below shows what I’m talking about.
The second problem is that if you need to make a bunch of tiny disks it’s very hard to keep them in one place. Many is the time I’ve need a dozen little disks, punched out 12, then spent 20 minutes trying to find all the little buggers.
The “punch board” shown below solves both these problems. Because the striking end of the punch touches nothing except the plastic the disks are pristine. The holes are perfect catch-alls for the disks if you need to make more than one. Problems solved!
It is simply a piece of 5/8″ pressboard (also called millboard, pasteboard, composition board, chipboard, etc.) with 1/4″ and 1/2″ holes drilled part way through. It needs to be wide enough to easily support your die base and long enough for simple handling. Mine is about 3″ x 7″, but there’s nothing magic about that. This is so simple to make it requires no elaboration.
Using the punch board is also super simple. Just position your punch and die directly over the hole and strike the metal punch with enough force to pierce the plastic sheet. The plastic disk will either fall into the hole or will stick to the end of the punch. Either way, since the punch itself is not striking anything but the plastic sheet, the disk comes out pristine every time.
One last note. You probably know the punches in the Waldron sets are actually injection mold ejector pins. Why he chose 2″ long pins instead of 1-1/2″ long pins is beyond me, but the excessive length is an accident waiting to happen (ask me how I know). With the very thin diameters especially, once the pin is placed into the die hole and the striking end of the pin is in contact with the plastic sheet, be sure to carefully support the pin above the die with your hand or the pin can rather easily bend. This is a simple but very expensive mistake to make. Note this has nothing to do with the punch block described above (and showing in the photo below), but wholly with failure to properly support the pin when it’s struck.
Good luck and good modeling,
Dave Klaus