Bridge To Nowhere… Part 1

or: The Enthusiasm and the Doubt

Due to other recent workshop commitments, and various demands on my time, the first opportunity I’ve had to work on the parlour guitar in 2016 came in late February. To be honest I find any lengthy period of time away from a significant build to be quite difficult – as I lose momentum it is easy to start focusing on the details of the build that I wish I’d done differently, and dwelling on any mistakes. The mind starts to play tricks, and convinces me that a perfectly good project is just glorified firewood – the enthusiasm starts to be replaced by a lingering self-doubt, and the incomplete parts of a project seem to taunt me. They say that sharks die if they stop swimming, and in a way large builds in the workshop can face a similar danger. I’m sure I’m not alone in feeling like this – most woodworkers I know have had a crisis of confidence over a big project, normally at a critical stage in the build (although there is the distinct possibility that I’m just a nut job). The best way I’ve found to respond to the mind’s treachery is to double down on the stalled project, because inevitably the project is in much better shape than I remember it and those catastrophic errors are simply not present.

So it was starting to go with the parlour guitar but fortunately getting stuck back into work, even on the mundane task of preparing an ebony bridge blank, was enough to dispel the growing self-doubt and get this build back on track.

The bridge of the original 19th century parlour guitar, on which this instrument is based, was 22mm deep with a straight saddle. Intonation on fretted instruments is always something of a compromise, but to my ears a straight saddle represents a compromise too far, so I decided to widen the bridge a little to allow for a compensated saddle. Increasing the bridge depth to 25.4mm gave me the necessary extra real estate without making the bridge look too heavy given the small body of the parlour guitar. The width remained at 149mm, as per the original design. I’ve always been a fan of the early Martin pyramid bridge design, but I’ve never had the opportunity to carve a pyramid bridge for any of my guitar builds. The pyramid wings will suit the parlour guitar’s aesthetic perfectly, so instead of the scalloped wings of the original guitar I’ll be carving pyramids for this instrument, which I’m greatly looking forward to.

IMG_2503

The bridge blank secured on the shooting board by a 5-minute jig

Securing small work pieces can be tricky, particularly when it comes to planing small pieces on the shooting board. My solution for this was to make a simple fixture to hold the bridge blank in place. I marked out a recess 20mm deep and 174mm long (the length of the bridge blank) on a large piece of 6mm thick scrap pine. I defined both ends of the recess with my carcase saw, and while I was at it made a couple of relief cuts across the width of the recess. It was then simply a case of knocking out the waste with a 1″ chisel and mallet. The bridge blank then pressed tightly into the recess, and the larger pine piece was easily secured on the shooting board by way of a holdfast. The tight fit of the bridge blank meant that the work piece did not slide under pressure from the plane, which makes for a much less frustrating experience.

IMG_2492

The Lie Neilsen No.51 shooting board plane and hold fast by Black Bear Forge are a fantastic combination

My main concern when shooting both long edges of the bridge was for a straight cut the length of the work piece, and which was bang on 90 degrees to the bottom of the bridge blank, with no undercutting. At this point I’m less concerned about the top surface, as this will be shaped once the bridge is fitted to the soundboard, but the bottom, front, and back all need to be perfectly square to each other. In the past I’ve used my Lie Neilsen 212 small scraper plane to dimension blanks, but for this bridge I wanted to see how the larger No.51 fared for shooting smaller work pieces. Needless to say, with a freshly sharpened blade, some careful setting of the blade’s lateral position, and the bridge secured in the jig, the large No.51 made relatively easy work of what can be quite a fussy job.

IMG_2518

My 12″ Bad Axe carcase saw is the perfect lutherie saw, here you can see the guide kerfs prior to trimming the bridge to length

With the long edges trued up, I then cut the bridge to length.  For this I struck a line for the first end on all four sides of the blank with a sharp marking knife, before trimming the blank using my Bad Axe 12″ carcase saw. I wanted this cut to be as accurate as possible and to need minimal clean up. This saw leaves a very good finish behind, so the only issue was getting out of the way of the saw and letting it cut straight and square. For critical cuts like this I prefer to make a shallow kerf on each of the four sides of the work with the saw, just to the depth of the saw teeth. When I come to cut the full depth of the work, the kerf creates a path of least resistance which the saw follows. The result is a square and true cut. With the first end trimmed I then struck marking knife lines 149mm along the blank for the other end, and having established my guiding saw kerfs on all four sides of the blank, trimmed the bridge to final width. Some gentle clean up with a 13 grain Auriou rasp and a Bahco smooth cut file, removed the saw marks, and the bridge is now ready for the gluing surface to be curved to match the curvature of the soundboard. But you’ll have to wait for my next post to read about that…

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s