© 1996, Nigel Cliffe and the 2mm Scale Association.
This article document was first published in the 2mm Scale Association Magazine. It is the first of three articles describing a drilling machine and lathe which can be built at home with minimal tools. The machines were designed for 2mm scale work (comparable to N), though are suitable for making small components in HO/OO.
The original machines were designed around Minicraft tools, which are widely available in the UK. The designs could be easily modified for other manufacturers ranges, such as Dremel.
All the photographs except the drilling machine were taken by Peter Clark, though errors in scanning and converting to JPEGs and GIFs are Nigel Cliffe's.
The "Fonly" family was designed by Peter Clark to provide quality machine tools at a low cost for the model maker working in small scales, particularly 2mm/ft. The family includes a lathe with light milling capabilities and a drilling machine. Each one is powered by a Minicraft Buffalo or similar mini-drill. If you have been to IMREX, or various Association events over the last three years you may have seen an example in action. The precision in the machines comes from alignment after the components are produced, so construction does not require special accurate machinery.
The drilling machine is the simplest to construct, and probably one of the most useful tools to add to the collection. It enables the user to produce holes which are perpendicular and allows concentration on drilling pressure and depth, without the fear of a skewed hole. Moving the drill "off-axis" is the most common reason for breaking small drill bits, and the drilling machine will prevent this happening. Whilst it looks a little odd, it is easy to use, and has less radial movement than common commercial minidrill stands. This very useful tool can be constructed in an afternoon, using only common hand tools.
Before we start, a word of caution. All tools should be handled with care and treated with respect, machine tools the more so. Materials should be held in suitable holders, such as a vice, and not held in the hand. Rapidly rotating metal can cause very significant injuries. Eye protection during construction and use are recommended.
The drill stand is made from birch plywood. In my experience, this is not available in DIY superstores, the soft red ply is not particularly good. I bought my ply from a timber supplier who sold it pre-cut in 600x600mm squares. Before you buy, check the inner layers of the ply aren't the cheap tropical redwood with a birch face, the proper stuff is available inspite of what many shops will say. I used 12mm and 6mm plywood, though very little 6mm is required. An alternative to ply is maple, but it is hard to find and very expensive!
In addition to the plywood, two 300mm lengths of straight 8mm round steel rod are required. Ordinary mild steel (bright finish) is ideal for this, and is available either as an offcut from an engineering works, or from the model engineering supply trade (adverts in Model Engineer).
Wood screws, washers, rubber band and glue (eg Resin W) are required for assembly.
There are many makes and types of mini-drill available from a variety of sources. As with most tools, quality varies and is partially related to the cost of the items.
The very cheapest mini-drills consist of little more than a 12volt motor in a plastic case, with a small chuck on the spindle of the motor. The bearings are not designed for lateral loads, nor are the chucks particularly concentric. They can be used in the drilling machine, but are not as accurate as the more expensive types.
Better mini-drills have a separate output shaft which runs in accurate bearings. This is connected to the motor through a coupling which prevents loads being directly transferred to the motor armature. Examples of this type are the Minicraft Buffalo and Impala ranges. If you buy a Buffalo, go for the MB1010 with small keyless chuck as a collet chuck and a larger 6mm 3 jaw drill chuck can be fitted to this, whereas the 6mm key operated chuck on the MB1012 is not removable.
Cutting out and basic assembly
|12mm Ply:||Base, Front Plate, Vertical Support, Four Rail, Clamp Blocks, Spacer for drill cage.|
|6mm Ply:||Drill Cage base, Drill Cage top|
|Metal:||Two rods, 300mm*8mm dia mild steel|
Cut out the large parts for the stand from 12mm ply. The exact dimensions don't matter, though two sides of the rear triangular support must form a right angle. Drill and countersink holes in the base plate and front panel, and screw and glue the stand together (figure 2).
Cut the steel rods to length, and cut four V-blocks from 12mm ply. Note that when assembled, a pair of blocks do not meet (figure 3). I made the V-slots by cutting a vertical saw cut, then opening out with an old coarse 10 inch metal work file, and finishing with glass paper wrapped around a block. Carefully drill holes in the blocks.
Open the vertical holes oversize in the large top V-block, washers are used on the screws, and movement in these holes is necessary for later alignment. Assemble the lower V-block with the steel rods, and screw up tight. Screw the upper V-block around the top of the rods, and screw the upper V-block to the top of the front panel, using large washers on the screws. Don't tighten the last two screws fully yet (figure 4).
The plans assume the Minicraft Buffalo MB1010. If you have a different minidrill, alter the dimensions to suit, figure 8 shows the minidrill in the cage. The important dimensions are the two diameters of the drill body. These are taken near the chuck over the main bearing, and along the body of the drill. Cut the lower hole as tight as possible, so it grips the minidrill tightly. The spacer must have parallel edges. Fix two small bolts to the upper part of the drill cage to attach spring or elastic band later.
Glue and clamp the base to the spacer. Drill oversize screw holes in the top, and fix with screws and washers to the spacer. Don't tighten the screws fully yet (figure 7).
Firstly, the rails on the stand must be aligned. Consider the drill cage - this has one flat grove and one V-grove. The V-grove must run on a rail which is vertical in two directions, the flat grove runs on a rail which is vertical in only one plane. Begin by setting both of the rails at right angles to the base. Gently tighten the fixing screws. Now adjust one rail (which carries the V-grove of the drill carrier) to be vertical in the other plane. Re-check both measurements, and tighten the fixing screws.
Finally, the drill cage must be set up. Chuck a piece of straight bar in the drill, and fit the drill to the cage. Use an elastic band or a spring round the body of the drill attached to the two bolts to hold the drill in the cage. Hold the cage to the rails, and adjust the top of the cage until the bar is perpendicular to the base of the stand in both directions. Tighten the drill cage top screws and re-check.
The cage will run better on the rails if lubricated with a little wax polish (the solid type), or candle wax.
Using the drill stand
The stand works best if clamped to a workbench or table. The work piece should be held in a suitable vice and NOT held in the hand. The drill cage with drill is held against the rods and moved up and down as needed.