DIY: LASER-CUT ROUTER TEMPLATES

Background

Flush-trimming router bitI often require matched sets of components for my projects (most recently on my 'Houdini' dinghy project). The simplest way to do this is to stack several sheets of material on top of each other and use a jigsaw to cut around a shape drawn onto the topmost sheet. This method has two major drawbacks: the jigsaw can leave a pretty rough edge (especially on plywood); and any error is duplicated on all pieces. A better way is to make (and correct) a single template component and then duplicate it with a router.

A flush trimming router bit allows you to duplicate the shape of a template exactly. To use it, you temporarily secure the sheet-to-be-cut to the template and then run it through your router such that the router bit bearing rolls along the edge of the template. If your router is mounted in a bench, then the template sits on top of the sheet-to-be-cut. If you're using your router 'freestyle', then the template sits under the sheet-to-be-cut. To reduce the amount of work that the router has to do, it helps to trace the template onto the sheet-to-be-cut, and then jigsaw around this line plus a few millimetres stand off. Use a flush trimming router bit in your router to finish off.

Laser-Cut Templates

Using a jigsaw-cut template is fine, but an even better option is to use a laser-cut template: the resulting components are more precise individually, and components that fit together do so with much greater accuracy.

I use the Ponoko laser-cutting service to make my templates. I normally use their double-sided whiteboard material (MDF coated on both sides with melamine plastic) as this provides a sturdy template with a low-friction surface. Obviously it is possible to get Ponoko to cut the components themselves, rather than a template for the components, but a template allows you to duplicate the component as many times as you like, and allows you to shape materials that Ponoko doesn't/can't provide. It also allows you to combine more than one template to produce the final component.

If you're interested in taking this into 3-D, see my Cyborg CNC pages. But first up, check out the 2-D approach...

A Simple Example...

Here I'm using a laser-cut template to shape two different sets of components for my dinghy. In the first case I'm duplicating the template exactly to make a distinct component. In the second case I'm using the same template to constrain the shape of a much larger component.

Create a discrete component
Create a discrete component
Here I've used my template to shape a discrete component.
Template part of a larger component
Template part of a larger component
Here I've used my template to shape part of a larger component (not very obvious in this photo unfortunately).

A More Complex Example...

Hatch cross-sectionHere I'm using a nested set of laser-cut templates to shape a hatch (door). The hatch surround has two layers (orange and green in the image on the right). The hole in the lower layer is smaller than that of the upper layer in order to support the hatch. The hatch cover (blue) has a gasket (pink) fitted to the back to help locate it in the hatch hole.

To achieve this without the assistance of a laser-cut template would result (for me at least) in a much lower quality job, with a much less precise fit and overall shape.

Note that in this case I've got Ponoko to cut the template set from plywood so I can use the innermost piece as the hatch gasket in the finished product without needing to duplicate it.

This laser-cutting template is available free from my Ponoko Showroom.

Nested hatch templates
Nested hatch templates
This is the nested set of hatch templates (with the bulkhead that the hatch is going into in the background). Ignore the small, rounded-rectangular piece in the middle (it's a completely separate bit of the dinghy). Note that the bulkhead that I'm cutting into (the orange bit in the image above) is not yet attached to its backing (the green bit) - this makes it easier to cut both layers.
Outermost template used to rough out hatch hole
Outermost template used to rough out hatch hole
The 'outermost' template is screwed to the bulkhead and used to 'rough out' the hatch hole with a pencil and then with a jigsaw. Note that the jigsaw cut is several millimetres inside the pencil lines.
Hatch hole post routing
Hatch hole post routing
The flush trimming router bit is then used to finish the hole (the outer/larger hatch hole).
Middle template used to lay out hatch gasket hole
Middle template used to lay out hatch gasket hole
The bulkhead is now positioned onto the backing layer and the 'middle' template is inserted and used to lay out hatch gasket hole (again in pencil and then with a jigsaw). Note that we are tracing and routing the inside edge of the 'middle' template.
Hatch gasket hole post routing
Hatch gasket hole post routing
The flush trimming router bit is then used to finish the inner/smaller hatch hole.
Middle template used to lay out hatch cover
Middle template used to lay out hatch cover
The middle template is then used to lay out the hatch cover on a separate piece of plywood. Note that in this instance we are tracing and routing the outside edge of the 'middle' template, and that I've reassembled most of the template set to provide some support to the template when routing around the outside edge. A similar result could have been gained by tracing and routing the inside edge of the 'outermost' template, but doing it my way results in a fractionally smaller hatch cover (due to the laser cut kerf) which means the hatch cover is not too snug a fit.
Finished hatch and cover
Finished hatch and cover
Finished hatch and cover (front)
Finished hatch and cover (front)
Finished hatch and cover (rear)
Finished hatch and cover (rear)
The finished hatch and cover. Note the plywood gasket glued to the back of the hatch cover.