Here's an example of a typical worktop jig. The jig is made to be used from both sides and has a variety of holes drilled into it to accept pins.
If spare sets of pins are available - get some!
The holes marked "F" are for use when cutting female joints, those marked "M" for use when cutting male joints and those marked "C" are for use when cutting the butterfly bolt slots (used to insert mechanical fasteners from below). Jig markings may differ - I've used these letters for clarity.
The numbered holes are used in certain parts of the operation to select the correct worktop width (in millimetres).
|The diagrams opposite show the terms used in identifying the
joint to be cut.
The following example will feature a 90° Left Hand joint.
In my drawings, the jig has a slight transparency, again for clarity. Real jigs are not transparent!
I tend to cut the female part of the joint first. This is done with the worktop laminated surface uppermost and the post-formed (rolled) edge facing towards you. It's often a good idea to leave the factory wrapping in place, to stop any accidental marking. I usually just peel enough away so that the cutting area is exposed.
Insert a pin into the relevant worktop width hole - in this example, I'm using 600mm wide stock. Insert three further pins into the jig in the holes marked "F" (all pins shown in red). Register the "F" pins against the post-formed edge and the width pin against the right-hand edge of the workpiece. Clamp the jig to the worktop - it helps if you can also clamp the worktop down in the same operation - if not, clamp the worktop down separately (there will be sideways pressure from the router, so the last thing you need is the worktop skating about whilst you're cutting!). Make certain that the clamps will not impede the router - a dry run is the best way, but be careful to ensure that the cutter will not touch the laminate, as worktop cutters are long and can often protrude below the base!
Now you're ready to perform the cut. Mount the relevant guide bush (usually 30mm) into your router base (or sub-base) and insert a good quality worktop straight cutter of the correct size and length - usually 12.7mm x 50mm (½" x 2"). Good quality cutters really pay off - don't be tempted to use a cheap cutter, as this will affect the finished result.
Don't try to take off too much at a time and never try to remove more than 10mm in one pass. I usually set for an initial pass of about 3mm - this gets through the laminate and provides a clear indication of the cut. Begin the cut FROM THE LEFT and with the guide bush registered against the edge of the slot closest to you.
Ensure that the router comes to a complete stop before removing it from the jig, re-positioning it, increasing the cut depth and repeating the cut. Continue this process until the joint is cut.
Now make a final pass, this time registering the guide bush against the side of the slot furthest away from you. This will give a cleaning pass to the whole surface of the joint.
Now for the male part of the joint. This is performed with the laminate FACE DOWN (using the other face of the jig), so make sure that the bench or trestles are free from debris.
Most jigs come with simple instructions to calculate the positioning of the jig along the workpiece in order to cut a specific male length - to fit into an alcove, for example. My jig (from Häfele) involves subtracting 228mm from the intended length, then setting the jig at the resulting distance from the opposite end, but this may differ between jig manufacturers. A pencil line is drawn after calculating and the base of the jig is registered along that line.
Insert two pins into the holes marked "M" and register the pins squarely against the post-formed edge. Remember, the laminate is face down, so if you're in any doubt, look underneath to check where the post-formed edge is! Use the pencil line to finally position the jig.
Clamp the jig to the worktop, again making sure with a dry run that the clamps will not interfere with the router.
Once again, begin the cut FROM THE LEFT and with the guide bush registered against the edge of the slot closest to you. As before, make a final cleaning pass, with the guide bush registering against the side of the slot furthest away from you.
N.B: If I am cutting a joint on a worktop that has a "free" end - for example, an "L"-shaped surface where one end does not reach a wall - I prefer to cut the joint in the end, then offer up and cut off the waste accordingly, using the router and a straight-edge clamp.
However, if you choose to use this method, make sure that you re-inforce the straight-edge clamp with a separate clamp, at least at the post-formed edge, as I've found that the rounded edge can cause straight-edge clamps to pop off easily.
|Having cut both parts of the joint, the shaped slots for the mechanical fastenings ("butterfly bolts") now need to be cut in the underside of the workpieces.|
Dealing with the female bolt recesses first, position the workpiece with the laminate face down - make sure there's no debris on the bench first! Insert pins into the connector holes (the holes marked "M" often double for the side-registers, but the jigs are clearly marked). Register the pins against the female cut-out and the PLAIN edge of the worktop.
Clamp the jig into position - you've got quite a bit of workpiece to choose from, so impeding the router is less likely.
Set the final cutter depth accordingly - usually 20mm, but check the depth that will be needed by the fasteners you'll be using. The deeper you rout here, the weaker the worktop will become, so only recess the fasteners to ensure they won't foul anything when fitted - 1mm clearance is enough.
Make a series of light passes, never more than 10mm depth increase at a time. Remember to work clockwise for the kindest cuts. Ensure that the router comes to a complete stop before changing recesses. Clean the recesses frequently - this is kinder to the cutter and prevents hang-ups on any loose bits that become trapped in the recesses as they're cut.
When the jig is removed, clean any rough surface edges from the recesses with a razor blade or similar - this ensures that if you slide the worktop into position over base units, the underside surface won't get torn as you slide it - looks better, too!
|Finally, the male bolt recesses need to be routed. Once again, position the worktop face down - ensure no debris on the bench. Insert pins into the connector holes as before, then register the pins against the front of the joint and the plain edge of the workpiece. Rout out as previously described.|
If you need to cut a male part of the worktop to a specific length, using the offset measurement provided for the jig:
Take your time, think things through first and everything will be fine!