2010 CNC Workshop

I’ve been attending the CNC Workshop since the very first one (circa 2004 or so). The event’s host and organizer, Roland Freistadt, passed the reins over to Village Press after the 2008 event, and we finally had another workshop this year.

"Cheap and Free" Rick Chownyk with the world famous Rick-O-Matic, a tabletop CNC machine he built out of various scavenged parts.

As always, Rick Chownyk had presentations on getting started in CNC.  Although I’m past the point of ‘getting started’, Rick is such an entertaining person that I just had to sit in on a session.

Rick's Thursday aluminum casting - the block on the right is just a Mickey Mouse logo, while the block on the left is a woman's head (fresh off of a Tormach machine) that became much more recognizable once bead blasted. These were created from foam cores.

Rick also does a demonstration of backyard aluminum casting.  While I’ve never tried it myself (and don’t currently have a need for it), I’d be quite confident in the procedure after seeing Rick explain and illustrate the process.

The two neatest new things at the workshop were Carmen Gianforte’s miniature firearms and Helmut’s (whose last name I didn’t catch) homebuilt wire EDM machine.

An actual Remington Derringer, and one of Carmen's 50% replicas

Despite having an interest in firearms, I know almost nothing about the field of miniature firearms.  Carmen explained that they are not models, but are sub-scale replicas, and as such are fully functional.

A glass display box showing some of the component parts
A more complete selection of some of the minature parts for one of the Derringers - all the screws are single pointed on a lathe!
A variety of objects on Carmen's display table. In the far upper left, a cutaway of one of the brass cartridges that was used to check for correct drilling depth in the prototype stage. To the right of that is the smallest bullet mold I've ever seen. Below that is another epoxied cutaway, this time of Carmen's latest miniature project, a knuckleduster revolver. In the upper right are the molds used to form the Alumilite grips. And the Winchester primers are what he uses as the source of the mercury fulminate for his own miniature primers.
The frame and barrel are investment cast, but Carmen needs to supply wax masters to the casting company. He makes these masters in a multi-part process with custom injection molds. The bottom left shows the first part - water soluble wax is formed into a 'core'. This core is then placed into another mold and standard blue casting wax is injected into the cavity, yielding the piece seen in the lower right. Carmen then drops these pieces into a tin of water and lets the water soluble wax dissolve away overnight, leaving the hollow wax part in the upper left (such a part would require terribly complex molds to create in one pass without a disposable core). The resulting stainless steel frame in the upper right is what comes back from the casting company.

When I say ‘fully functional’, yes, that means they actually shoot (they even have rifling in the barrel bores).  Carmen actually manufactures his own ammunition – I forgot to ask what caliber, but they looked to be around .125″, perhaps less.  Making the cartridges is fairly standard (if eye-crossingly tiny) lathe work.  But they also need primers, and Carmen makes his own – anvils and all.  It took him an immense amount of trial-and-error work to draw the tiny copper discs into cups with a set of progressive dies and punches.  For the mercury fulminate, he takes shotshell primers and adds a few drops of water to desensitize the compound, and is then able to smear a bit of the resulting paste into his own primer cups.  After pressing these primers into the cartridges with anvil in place, and allowing them to dry, the cartridges are live and can be fired.  I have no idea how he adds powder and seats the bullet – I had so many questions for him that I could have quizzed him for a week, yet he very graciously answered all my questions and happily explained his techniques.

Helmut’s wire EDM was a fantastic little machine:

A wire EDM machine uses a copper wire as an electrode to cut a 2D shape in a plate of metal, just like if you took a hot wire to cut a shape in a stick of butter (just much more slowly).  Generally wire EDM machines are very large, expensive machines – this is the only homebuilt one I’ve even seen in person, and it’s a clever little contraption.  Helmut is able to pull the whole machine up out of the tank (which is filled with distilled water) to inspect progress and make adjustments.  The pencil on the back side traces out the pattern being cut (stars in this case).

9 thoughts on “2010 CNC Workshop”

  1. Benny –

    It seems there’s a great deal of interest in Helmut’s EDM, and I managed to track down his information. His full name is Helmut Hummel (Hummel Precision) and his gmail address is edmman2.

  2. Well, this one was homemade – if you’re looking to purchase one rather than build, I’d check with a local machinery dealer or check Surplus Record for a used machine.

Leave a Reply

Your email address will not be published. Required fields are marked *