Saturday, May 19, 2012

Binding

The guitar with binding is pictured at left.  I mentioned that I wasn't happy with the way the binding went on my guitar, so perhaps a word or two of explanation.   I put it on in the standard way -- that is, I bent it to the shape of the guitar, and glued it in place using painter's tape as a clamping mechanism.   The channel cutter did a perfectly fine job of cutting the channel at a consistent depth around the guitar.  It's depth was shy of the thickness of the binding material (maple) or the binding material was proud of the guitar, and you can see the shavings where I scraped it down to be flush with the sides, soundboard, and back of the guitar.  All that works pretty much as advertised with a couple of exceptions.

Let me talk about the intersection of the back and the tail block.   Looking at it straight on, I think I did a reasonably good job of getting the two pieces of binding material to come together in a tight seam.  That too I did in the standard way.  I glued one piece of binding in place, then trimmed it back to the center of tail block inlay using a razor saw (cut at an angle) then a chisel.  The second piece of binding was glued in place up to the first, and I cut it away with the razor saw, then tweaked its fit carefully with a file.  I did the same on the soundboard side.  As I say, I am relatively happy with the way it came together.

 Looking at it from another angle, you can probably see the flaw that is annoying me.  I'm not entirely sure what I did wrong, but there was a gap that showed up between the back stripe and the binding.  I had cut the purfling channel not quite up to the back stripe, and then cut the binding channel.  I cleaned up the purfling channel to the back stripe with a chisel, and then glued the purfling in place.  I did the miters with an xacto knife.  The purfling was, or so I thought, flush with the binding channel, but when I removed the tape and scraped it flush with the back, there was a gap.  I filled it with epoxy and maple dust, but it is still visible.  Not completely happy with that.

There was another issue with the binding around the guitar.  I cut it too thick, and so I had difficulty getting it to set properly in the binding channel, and the tape didn't provide enough clamping pressure to keep it tight against the channel while I was doing the fitting.  Here again, I got a couple of gaps around the periphery of the guitar.  Again, I filled them epoxy and dust, but I can still see the gaps.  Not completely happy with that either.

My solution goes something like this.  Patience is a virtue, and one that I sometimes lack, but first, since I am cutting the channels with a rabbet bit and bearings, I should cut the channels for the purfling and the binding on the guitar body.  I can then use the channel itself to cut and finish the binding material to thickness.  I would still want it slightly proud of the channel to be scraped flush, but it would be considerably thinner, and the spring back after bending more amenable to adjustment with the tape's clamping pressure.

Sunday, May 13, 2012

Been Some Time

It's been some time since my last post, but life in Academe heats up over the latter part of April, first part of May -- all the celebrations leading to graduation.   I did fit the back and soundboard of the guitar, and glued it up.  You can see it in the photo at left. 

There are a couple of things I would do differently.  First, there is order of precedence.  I would glue up the back first.  It seems a well-duh! moment, but it's difficult to clean up squeeze out through the sound hole.  Second, I took the guitar out of the mold when I installed the end graft, and didn't put it back in.  I have had an idea for some time now to leave the guitar in the mold, and use violin clamps to glue up the back.  Once the shape has been determined, it can be removed from the mold to glue up the soundboard.  Third, I need to make a bevy of violin clamps.  It's possible to use various and sundry clamps, as I did, but the violin clamps would make it so much easier.

I did do some work on the binding channel.  I have pictured the binding jig in a previous post, but you can see it above, ready to use.  The guitar sits in the cradle, and the jig rides along the side as you cut the binding slot.  Some additional pictures are below to give some idea of the construction of the cradle and the jig.  Pretty simple stuff really.  The jig is essentially a drawer riding on metal full extension slides, which allows for up and down movement.  The hole at the top of the drawer is the "grip" for setting it down on the guitar.  NOTE:  do this carefully, particularly, on the soundboard.  Don't want to mar good work.

The router is attached to a plexiglass base that is inserted in the slot that you can see in the drawer toward the bottom.  It fits snugly for the moment, so I didn't put in a planned locking mechanism, but it would just be a set screw through a hardwood block above or below the slot.

In the photo at left, you can see the plexiglass base.  It is shaped to avoid touching the guitar except at very specific locations on the top and sides.  I use a rabbet bit, with a set of replaceable bearings.  There are other ways to do it, but I had the bit, so might as well use it.  I can get pretty close to the right depth, and I always make the binding a bit proud regardless, then scrape it down to final thickness after I've glued it up to the guitar.

The cradle is pretty straight forward as well.  It's just cut to the shape of the guitar, with the rests that you can see pictured below.

 As I said, I've cut the binding slots, and I did it by setting the guitar in the cradle, leveling it, and then running it around the edges of the guitar.  I'll talk a bit more about installing the purfling and binding in the next post, but I am running into some difficulties.