The tool of choice here is a 185mm circular saw, which has sufficient capacity while being small and light for easy handling.

I often use the saw with the adjustable side fence but get very frustrated with its limited capacity and the difficulty in maintaining a straight clean cutatthe end.

I find that this fence has mostly left the board before the heel of the blade has, and I struggle to finish the cut accurately, often ending up with the heel of the blade causing a problem.

Making the jig

After marking the footprint of the base plate on the MDF, the blade was plunged through the MDF creating a blade slot. The saw was then removed from the MDF again. The screws and marking allow the saw to be re-attached in exactly the same position.

Next, the length of meranti was trimmed to 40mm by 8mm, then crosscut into six lengths. (2=1000mm, 2=250mm and 2 =11 Omm). The two long strips were intended as sliding extension rails or arms, and the short strips as supports for these rails.

The short strips were then attached to the MDF base, two in front of the footprint of the saw and two at the back, leaving space between the rails to slide back and forth snuggly.

Care was taken to attach the strips square to the blade slot previously cut through the MDF and parallel to each other.

A further strip of MFD was glued to the end of the two rails ensuring that the strip was parallel to the blade slot, thus creating a sliding fence which is also reversible, allowing the fence to be slid out and inserted from the other side.

Once the glue had set, the fence was removed and the base trimmed and cleaned up all around. The side of the jig where the saw blade slot is, was trimmed back until the outer edge of the slot was removed, thus allowing the fence to be set almost up against the blade. (Graphic 2).

The saw was re-attached and the first testing was done. The saw was effective and the new fence allowed strips of up to 700mm to be cut from the board. There remained two problems still to overcome.

A method was required to lock the sliding fence at the desired width, and some form of support was required behind the heel of blade to assist in keeping the saw running straight during the last section of the cut.

Problem solving

A careful cut was then made along this line up to about 20mm from the back of the blade slot.

This section was then trimmed off and a 50mm length of 20mm aluminium plate was drilled and countersunk and attached onto this cut out allowing the plate to protrude about 15mm below the MDF base.

This plate would effectively run inside the track cut by the blade and also press up against the newly cut edge of the board, providing the much needed support for the heel of the blade while running out at the end of the cut.

The last problem was tackled by making two clamps from off cuts of 25mm x 5mm mild steel flat bar, 8mm round bar and two 8mm x 75mm bolts and nuts.

Two pieces of flat bar were cut and drilled then two short lengths of round bar were bent into "L" shapes and one end welded to the centre of the flat bar.

The nuts from the bolts were then welded to the other ends of the round bar. At the same time, two short lengths of round bar were welded to the bolt heads creating a sort of wing nut. These parts were wire brushed and painted.

The saw was then removed from the jig and the jig was placed on the drill press and two holes were cut through the top covering MDF using a 25mm hole saw. This exposed and provided access to the sliding fence rails below.

The two MDF circular plugs removed from the hole saw were then threaded to accommodate the 8mm bolt.

The two clamps were positioned and screwed to the jig allowing the bolts with their wing nut to pass through the welded nut and screw snuggly into the threaded circular plugs.

The plugs then passed through the holes in the top MDF and rested on top of the sliding rails. When the wing nut is tightened, the plug effectively applies pressure to the sliding rail preventing the rails from sliding.

The jig is very basic and cheap to build and has proved to be very effective. In fact I'm so pleased with the results that the old saw, which has earned the right to semi-retirement, will stay permanently attached to the jig for those big boards.

A word of caution, the current design has secured the blade guard in the retracted position thus creating a potential hazard, but with a bit of fancy marking and jigsaw work, an opening could be made to allow the guard to slide through the jig and perform correctly.