I recently received as a birthday present, the Great Planes Slot
Machine. I had inspected one of these gadgets at Texas RC Modelers a couple of
weeks earlier and while I thought it was interesting, couldn't see an immediate
need for one. Remember, only a couple of months ago I published a nifty
suggestion in the Tips and Techniques section of The Dawn Patrol on just this
subject - how to create slots for CA hinges. So surely I couldn't see the need
for this handheld, motorized hinge slotter. But, as usual, my wife kept asking
me "Isn't there some tool or kit or something you need from the hobby shop for
your birthday?" Being the kind and considerate person that I am, I toiled for
hours trying to come up with an idea for her (actually, about 3 seconds). I
reluctantly gave in and told her that I could use one of those motorized hinge
slotters. Needless to say, after looking at me quizzically, she asked "What does
it do?" We won't go into that dialogue here.So far I have not actually cut any "production" hinge slots with this nifty little tool. I actually don't have a plane on the assembly line right now (heaven forbid….). So I played with this gadget for awhile to get the feel for it. Let me tell you, I was pleasantly surprised at the results I was able to obtain with the tool.
The tool (see picture) fits in the palm of your hand and has a trigger which when squeezed activates the two counter-oscillating cutting blades (actually blades with cutting teeth). When placed upon a piece of balsa these two blades will cleanly and smoothly cut a slot just slightly wider than your normal CA-type hinge. There is another set of blades for pinned hinges (which must be purchased separately). The tool has little vibration and is fairly easy to handle when running. Lou Montanaro of Texas RC Modelers showed me a trick that makes the cutting easier. He begins cutting the slot by placing one corner of the blades on the balsa and then rotating the blades down into the wood. This prevents the blades from wanting to "skip' along the surface. Aligning the blades with the center line (cutting line) takes some getting used to. I found that by standing the piece to be cut vertically (as opposed to horizontally as GP demonstrates) I could get a better view of the alignment. After practicing awhile I was able to consistently cut very neat, aligned hinge slots.
The tools comes with "thin" blades for cutting CA hinges. Even at that, I was worried that the thickness of the slot was a little too much for the particular type of CA hinges I use - Radio South 1/4 Scale Pro Hinges. These are very thin, yet extremely durable hinges. I made a prototype trailing edge and control surface which I slotted and then glued in hinges. I was very pleased with the results. There was no way I was going to pull those hinges out without tearing the balsa up first. For other CA hinges (the white, more porous type) I think the slot thickness will be perfect.
So, what do I not like about this tool? Well, being the curious person that I am, I read the instructions on how to change the blades and thought I would give it a try. The first problem I encountered was that the screw that secures the blade holders in place was partially stripped. After figuring out what was going on, I was able to partially pull the blade holders out and then coax the retaining screw on out. Looks like a manufacturing/quality control flaw here. Each blade is held in place by two small bolts which require a phillips screwdriver. The nut on the opposite side of the blade is recessed into the blade holder assembly so no wrench is (theoretically) required to hold it when loosening or tightening. Each screw had some "lock tight" on it, which the instructions recommend using when replacing the blades. The first thing I learned about these screws is that the heads are very soft. Make sure that you use a high quality screwdriver that fits snugly into the cross-slots. Otherwise, as I did, you will quickly strip the head of the screw. Now what…. After some creative use of a Dremel tool, a drill press and a punch, I was able to extricate the bolt from the assembly. Luckily, not too much damage was done to the holder and I was able to replace the bolt and nut with a spare from my collection of odds and ends. A word of warning - be careful with the amount of "lock tight" used when replacing these bolts. Otherwise you may be calling me for guidance.
Other than those two problems the tools seems to be fairly well built. I'm not sure how long the blades will last, but unless you are cutting slots in ash or oak, I would venture to say that you can cut "lots of slots." Great Planes also advertises this as a cross-cut tool for cutting small balsa strips.
I think Great Planes has come up with a winner here. If you are a prolific builder and like to use CA hinges or flat pinned hinges, then this might just be the tool for you. Neat, clean, hinge slots in just a matter of seconds.