Half-edging with a router

A quick way to fit a new piece of wood to a block area

Mid-to lower-end instruments make up a large majority of the market for musicians, yet repair techniques for this level are not always the most publicised topic. I feel this area needs more coverage, as we all do this kind of work. These repairs still need to be done to a high standard, but also must be carried out in a cost-effective way.

Half-edging the top- and bottom-block areas after removing the front always comes as an inconvenience, and needs to be dealt with efficiently. As tempting as it is to use filler or thick glue (like the last person may have done), the surface may be so bad that a new piece of wood needs to be fitted.

This is not a technique I would use on something with historical value, but it is very useful for stock instruments, and budgets with less wiggle room.

As an overview of this process: I make a template and guide, route the surface, then fit a new piece and shape it up. The guide can be kept for future use.

The 2mm-thick template

1 To make the router guide, I first make a template with 2mm-thick plywood of the size I want my edging. An average top-block is 50mm wide so this needs to be slightly bigger: a trapezoid over 48mm long, 60mm at the narrow end and 70mm at the wide end. At this stage it is crucial to make the sides of the trapezoid straight.

Jigsawing into the 12mm plywood

ALL PHOTOS WILLIAM SZOTT

2 I then use this template to mark out the router guide on a 190mm x 220mm board from a thicker plywood (12mm). Then the board is nicely squared and a centre line is drawn. The cut-out is below the centre of the board. Making the trapezoid so neatly on the 12mm plywood would be very difficult by hand, hence why I have the template. Then I drill holes and cut out the guide with a jigsaw.

The flush trim router bit

3 I place the template over the 12mm plywood board, then using a flush trim router bit, route the cut-out. I now have a nice, neat guide.

The guide is perfectly straight with the front

4 I loosely clamp the front to the board. After eyeballing the centre line to confirm the guide’s straightness, I then tighten the clamps. The trapezoid guide can be moved up or down the body for a wider or narrower edging piece.

The board is clamped in a vice

5 Now I need to secure all of this for routing. Holding the guide in a vice may look precarious, but it works well.

6a How the bit looks in the router

6b The router ready to cut

6 Now the fun starts. I use a short flush trim bit (Axminster 952561 milling cutter of 12.7mm diameter, 8mm depth) and adjust the router so it protrudes 1mm below the guide surface and into the front. I work down in increments to ease the nerves. I go nice and slowly, so that there is very little pressure or stress exerted on to the front from the high speed of the cutter and the shallow depth of cut.

Trimming the wood flat

7 I cut the wood down as much as I need: usually 1–2mm. (All that preparation work and checking, just for two minutes of routing!) Now I have a perfectly flat platform for the wedge. The picture shows how the purfling is cut much deeper on the right side, and yet the edge hasn’t broken off.

8a The new wood is clamped to the front

8b The piece is left thick for gluing

8 I can now use the guide as a template for the new piece of wood. You could spend all day deliberating between which piece of wood to fit. Find something similar and get on with it.

The new piece finally shaped

9 Then I shape it down as normal, and I like to chalk-fit the piece to the block. On instruments with higher arching, the block area can sometimes look like a plinth when fitted on to a big block. It looks a bit odd, but it needs to fit.