Monthly Archives: April 2011

Bindings and Purflings

Had a bunch of starts and stops this past week but finally got something done today. That is the edge bindings and the purflings.

The edge binding is important. It is decorative but it also functions as a protective strip around the edge of the body. They can be wood or plastic and just in case you are wondering I am a woodworker not a plastic worker. The purflings on the other hand are mostly decorative and optional. The purflings are the decorative strip of marquetry inlay you might see on a soundboard between the edge binding and the soundboard. Both the edge binding and the purflings are delicate and fragile making them easy to break and difficult to work into shape.

I am using that curly maple to match the end graft and a herringbone pattern purfling to match the rosette. To bend them into shape I used my side bender with the heating blanket in the same manner as I did with the sides.

The purflings have to be bent on their side so the pattern is face up. They are dimensioned 1.5mm thick by 3.5 wide so bending them on the side poses problem like crimping and rolling into a twist. To keep them straight and flat I made a sandwich and taped them up.

Then I taped the sandwich to some spring steel in the center, end-to-end, and bend them with my Fox side bender.

The end result is nice. The purflings have a little crimping on the inside of the tight bends but it is not beyond workable. Also they lay flat, which will make glue-up less problematic.

The ones pictured above are not the ones I ended up doing today. Like I said I had some starts and stops. They are ornery critters and they gave me a bunch of grief getting them right. The edge bindings I did today are 1.5mmX4.5mm while the ones above are 3mmX4.5mm. A little too thick but I needed them to make a sandwich for the purflings. The purflngs I also had to go through two sets before I got it. First time was clumsiness and the second time was an error that just got worse each time I tried to fix it.

All said though, I now have a set of bent bindings and purflings ready to glue into place once I have the groove cut.

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Making and Gluing the End Graft

In the next step I will make and glue on the end graft. This is a tapered piece of quatersawn stock that seals up the tail end, where the bent sides come together.

For my end graft I am using some curly maple I have left laying around the shop from the Chef’s Prep Table I made last summer. This is where some luthiers get creative but this time I am doing a simple tapered end graft. I really like the tapered butt joint because it will be a perfect fit when it snugs up – no gaps.

My curly maple stock. For the taper I just eye the proportions. I think I had 35mm at the top and 12 at the bottom.

Put it in the vise and use a low angle to plane down to the line.

Ready to fit.

Marking the placement.

Start making a router jig.

The completed jig attached to the tail end of the body. Notice the napkin being used to protect the spruce top from the wood and clamping pressure. It worked great.

After a few test cuts on plywood I was able to set the correct depth. Here is a pic of the cut groove ready to accept the graft.

It fits perfect with almost no cleanup.

Glue it in place and clamp it with a caul.

A few hours later I took the clamps off and trimmed away the excess with a Japanese hand saw. Usually for this kind of flush cut trimming I lay a thin piece of protective stock and cut away carefully.

This turned out nicely. Once again I have confirmed best practice for so many things we do in woodworking are jigs and test cuts.

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Gluing the Back to the Body

Moving along. By the way my domain access problem was fixed. The admin of the web hosting company found there was a setting fault on their firewall. So I am back in business.

In this post I will glue the back on. Last time I went through the steps for fitting and gluing the top. Before that I fit the back but didn’t glue it as the top has to be taken care of first. So now that the glue has dried, cured and I’ve had my cup of coffee it is time to attach the back.

I put some pads down on the lifters because the spruce top will sit on them. That is one thing about this project; you have to be very mindful of what the spruce top comes in contact with because it dents so easily.

Then I glue on some side struts to strengthen the quatersawn rosewood against splitting.

Here I use some dowels to spread the body to the back that was fit in a previous step. It is not unusual for the sides to crimp or splay a little when one side has been glued on. This time though I can’t use the spreading clamps.

Sorry folks no picture of the glue-up as it was done in the same manner as the top. After the glue up I mostly used my low angle block plane to flush up the back to the side. other tools I used to help out were a file and rasp.

Here you can see a side profile with the back flush cut to the side. The dowels just lifted out.

Another profile shot.

A few more steps and the body will be done. Getting there.

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Fitting and Gluing the Top

Next step I will fit and glue the top.

In the last step I only fit the back as I had to fit the top after fitting and before gluing the back. The bent sides had almost no spring back after bending but they are not a perfect fit. Using the spreading clamps and dowels the body was pressed into the form and the back was fit. Basically the shape was then decided.

In fitting the top I use the same method for holding the body in shape. However there was one difference in the fitting. On the back I notched the kerf linings out so the braces butted against the body on the inside. But on the top once I had everything lined up and marked I notched out the positions by cutting through the body.

The reason for the departure was simply ease of doing but also I wanted one plate to hold the shape. On the back the braces are 90 degrees to the center line while on the top plate the braces are angled to the center line. Notching out the positions on the soft wood with such an acute angle I probably would have made a mess of things. So I did the cut through method. Both ways are standard.

The cut through notch. After lining up and marking I cut out the first set on the top bout. These act as my position register. With the first set done I then mark out the positions of the X-brace notches.

A close up of the cut.

Check the fit.

Doubling as a clamp I drilled holes on the mold to accept the clamps.

I was stewing about how I was going to do this and then decided on this. I had the clamps from before and they worked perfect in the body mold.

The dry clamp; everything fits in place nicely. The top is slightly arched so I can’t put pressure across it flatly. In this case I use some spot cauls with cork on the bottom facing the soft spruce top.

A side view.

The glue-up.

The top glued in place.

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