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Volume 3, Issue 6
August, 2003
Build This:
4" Lampara Shell
by Liquid Gold
Pages: 4
Class C Corner:
Megatron, N. Praying Mantis
by Kyle Kepley
Pages: 1
Design Notes:
Rolling Precision Round Stars
by Kyle Kepley
Pages: 3
Tool Tip:
Build Your Own Corning Machine
by Kyle Kepley
Pages: 3
Build Your Own Corning Machine
1 2 3

Figure 1: A simple corning machine that screens as it corns.

(4) 48" 2x4s
(2) 24" 2x4s
(1) 23" 2x4
(2) 11-3/8" long 1x4s
(1) 26" x 14" 3/4" plywood
(2) 23" x 22" 3/4" plywood
(1) 32" x 23" 3/4" plywood
(2) 16" diameter disks 3/4" plywood
(2) 11" diameter disks 3/4" plywood
(1) 14" long 1/2" wood dowel
(4) 14" x 1/4" x 3/4" wood strips
(1) 10" x 14" screen
(12) 3-1/2" long 1/4" lag screws
(12) 1/4" washers
(1) box 1.5" #8 wood screws
(1) 8" pulley
(1) 2" pulley
(2) 2" swivel casters
(1) 26-3/4" long 5/8" rod
(1) 24-1/4" long 5/8" rod
(4) 5/8" collars
(4) 5/8" ball bearings
(2) 21" long 5/8" I.D. heater hose
(2) 3" hinges
(1) 14" long 11" I.D. tube or pipe
(4) 2" long 1/4" stainless bolts
(4) 1/4" stainless wing nuts
(1) 32" bike tire innertube
(1) switch box
(10) pool balls
(1 ) 4L400 40" drive belt

staples, formica, contact cement, motor mounting hardware
With the increasing price of commercial black powder, many pyro hobbyists are trying their hand at making their own. The process is pretty straight forward: mill some good quality meal powder, perhaps using some home-made hardwood charcoal, then compress it into hard pucks and break them apart. Screen the crushed particles into the various sizes you want and there you have it.

Most pyros already have a ball mill and various screens. Hydraulic presses are readily available on the market or easily made. However, it is the process of breaking up the pressed chunks of powder, known in the trade as "corning," which results in the most tedious labor when making home brew black powder. The simplest and probably most common method for corning is to take the chunks and break them apart using the end of a wooden bat or some other blunt, non-metallic object. However, this method is time consuming and a little nerve racking for some. Even though black powder is very stable with regard to friction and impact, the corning operation is still the source of most accidents in commercial manufacture.

Corning BP by hand also results in more work, since the grains must be repeatedly screened during the process to keep from crushing the grains that are already the desired size. Without frequent screening there will be an overly large amount of "corning dust," which is the name given to the fine grains leftover after corning. Corning dust is too fine to be used for any kind of lift or break charge, yet too grainy to be used as meal powder. While corning dust has some good uses such as dusting over prime slurry or freshly made black match, the amount resulting from any corning operation is optimally minimized.

The two most common approaches to corning involve either impact or a grinding action. Some hobbyists feed large chunks into a set of parallel grinding rollers that have pyramid shaped teeth on them. The rollers are geared to roll in opposing directions toward each other, thus grabbing the chunks and pulling them in as they are ground. This method reduces corning dust and time spent screening, but is still a manual operation conducted at close proximity.

Figure 2: Corning and screening cycle for one full revolution.

The ideal corning machine should operate unattended, produce a minimal amount of corning dust and output a variety of grains that need no further grinding. The machine I have designed here does just this, and can process about a pound every fifteen minutes. The machine, shown in Figure 1, operates like a large ball mill with a screen built into the side. Each revolution of the large drum results in an impact stroke and a screening stroke.

As seen in Figure 2, the low RPM corning drum contains a single lift bar and a half dozen or so grinding balls such as billiard balls or something similar in size and weight. The lift bar catches the balls and carries them to the top of the drum, at which time they free fall to the bottom and strike the powder grains that remain at the bottom of the drum. The lift bar then comes back around and collects the balls while letting the powder grains pass between them. The powder then passes over the screen port, which removes any grains that have been reduced to the correct size. Because small grains are removed as they are produced, only the larger grains that still need to be reduced are subject to further impacts.

This impact/screen cycle results in faster corning with less corning dust while also freeing up the operator to do something else with his time. I find that this machine can corn powder at about the same rate that I can press it, so I will let the machine work on one 1000 gram batch of pressed chunks while I prepare the next 1000 gram batch.

The catch box built around the rollers also make an excellent area for screening the finished product, since there is plenty of room to vigorously shake the screens and the chute makes collecting the results easy. I place a table under the mouth of the chute so that the grains can be swept out onto a sheet of poster board for easy transfer into screens, containers or wherever it needs to go.

The remainder of this article describes how to build the machine shown above. A future article will describe the entire process for using this machine in conjunction with a ball mill and a press for making commercial quality black powder.

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