Most of my model rail layout is built on small standard modules - an open bottomed box 22.4 inches by 15.25 inches by 3 inches deep. The size of these was predicated on fitting in the cardboard boxes that my stationary supplies arrived in. Serendipitously this means that the module is small enough to work on using my Work Station and, using a scale or 1 cms to 1 inch, I can make a drawing of a module on standard A4 paper (or for my American friends Letter sized paper).
For the sides I use the mitre saw to cut 3 inch wide plywood strips in to lengths very slightly longer than 22.40 inches (the slight oversize can be planed or sanded off once the box is made up - see Assembly later).
Connectors - the modules are joined using M6 (1/4 inch) hexagonal head machine screws. But instead of using a nut to fix these I use Pronged Tee Nuts fitted into a backing strip of wood.. The holes are positioned 1.5 inches up from the bottom of the end strip and 4.0 inches and 11.25 inches in from the back. The Pronged Tees are fitted at the front of the left hand end of the module and the back of the right hand end of the module (to allow the modules to be flipped end to end). Connecting holes in the same position can be drilled in the front and back sides to allow a mix of landscape and portrait modules.
Pronged Tee Blocks: A series of 7mm holes were drilled (using the drill press) 44mm apart in a long strip of 10mm x 44mm wood. Next the strip was cut into 44mm lengths with a hole in the centre of each. A Pronged Tee was pressed into the hole by using a vice. (Initially I thought that I could insert the Pronged Tee buy inserting it, running in a machine screw and tightening to draw the Pronged Tee fully into the block, but found that this tended to split the block - so be careful.)
I used a drill press to drill the holes to ensure that they are perpendicular to the wood and not askew as would be if I had used a hand-held drill. (The cheapest option is to buy a drill stand that fits your electric drill - I got one for less than £10 ($15) but prices vary widely and can be a lot more.)
Positioning: To ensure that the modules would be positioned correctly before assembly I took left-hand end of one module and the right-hand end of the next modules, aligned them and the machine screws through the close fit hole and through the oversized hole into the Pronged Tee in a wood block and tightened. I then loosened and removed on machine screw and Pronged Tee block, put PVA glue on the block and refitted it and the machine screw. After tightening the machine screw, I removed the other block and glued it. This meant that the blocks were positioned perfectly to align the two modules exactly. Once machine screws were tightened, I put the pairs of modules aside for the glue to dry. As it is possible for the positioning of the 6 mm hole to vary slightly between modules, the modules should be identified. I numbered them so that initially the right-hand end of module 1 was aligned with the left-hand end of module 2. When the glue dried on the Pronged Tee blocks module 1 and 2 were disconnected and the right-hand end of module 2 aligned with the left-hand end of module 3 and the Pronged Tee blocks positioned and glued. The process was continued with 3 and 4, 4 and 5 etc.
Hole Drilling Jig
Doweling Bushes: Why such oversize holes when the connector holes were 6 mm and 10 mm? This was so I could insert metal doweling bushes that reduced the holes down to 6 mm or 10 mm. By using these bushes I ensured that drilling did not wear away the wood of the jig and enlarge the holes and the bushes helped keep the drill vertical. (You should not confuse doweling bushes with collars. Collars are used to prevent you drilling too deeply. The bushes are metal that fit in a doweling jig. The bushes that I used consisted of a stepped cylinder of metal. Serendipitously, I picked mine up for a few pounds at Lidl!
Cross Section of assembled Hole Drilling Jig showing End Clamps
I completed the jig by marking on it front, back and bottom on both sides and the left hand and right hand sides. Finally on the two sides I marked which hole was which. So, the left hand side had the small (6mm) hole at the back and the large (10mm) hole at the front and the reverse on the right hand side. by marking the jig this way I felt that I would minimise my making a mistake and drilling the wrong holes,
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Copyright 2011 Jeremy Hall