Maurice's cutting jig and cutter
One of the critical requirements for building model aircraft is making accurate joints - both for strength and appearance. With larger models I use a mitre box and a Zona saw, but these are inappropriate tools for small models built from 1.5mm (1/16") square stock and smaller. When you have such a small contact area for adhesive, angularity issues become a concern. For example, if you are building with 1mm (1/20") stock, an angle deviation of 0.5 degrees can eliminate 30% of the effective contact area for gluing. Now you could use PVA-based glues which provide some joint filling, and that may be an argument against such a need for accurately cut joints. But such glues are not designed as filling agents, and with an accurate joint, less glue is required. With cyanacrolyte based adhesives, if it doesn’t “smoke” when the joint is made there is too much gap with too much air, and the result is that the joint strength is compromised.
The principle joint requirement for modeling is a flat face. Some joints are compound in nature and difficult to cut. But simple angled joints are not difficult, and straight 90 degree cuts are the easiest. The jig I am showing below solves most cutting requirements, but as yet a compound jig cutter is still in the pipeline.
There are two parts to this cutting tool: the aluminium jig itself with a preset 90 and 45 degree guide and the double edged, wood mounted blade. These component parts are shown in the following photograph.
The preferred cutter is a double edged razor blade glued to a holding block. When fabricating the cutter, remember that the maximum depth of cut is 1.5mm (1/16"). The jig shown here has a cutting line of 45 degrees and 90 degrees pre-set. Other angles must be done “by eye” but that is not really a problem as the jig can be used “on plan” and rotated for the desired angle.
Exacto knives are excellent for larger work but do tend to crush before cutting... not desirable for small stock. The razor blade can eliminate crushing, and the cutter is best used in a slicing motion while being held against the face of the jig. This type of cutter is extremely sharp and as a workshop safety issue I would stress that it be laid flat, blade down, after use. I have found that one blade will last a long time; the blades do hold their edge well.
In the next photographs 1.5mm (1/16") stock is being cut at 45 and 90 degrees. The jig is simply placed over the stock, and the stock is held against the preferred side with the index finger. The cutting tool is then held flush to the right side of the jig to make the cut. Remember to cut with a slight slicing action as this makes for easier cuts and lessens the likelihood of the blade snapping.
Often it is best to work directly off the plan. Sometimes the simple act of transferring measurements to a cutting board can lead to errors from slipping or forgetting. Fine angles should not be dealt with in this way but cut directly over the plan. The photo below shows how this is done.
With practice you can find many ways to utilize this jig for making accurate and fast cuts. In case you are wondering about the hole in the jig I could say it was for hanging on a peg board, but the truth is it is an index hole used during the manufacturing process.
Happy cutting!