Joining the Back and Top

The first step for me is to join the back and sides. Most of the techniques I use are detailed in Cumpiano’s splendid book Guitarmaking with a couple of exceptions, most notably the power jointer.  I decide which sides I’m going to join, trim them to align the grain if needed or desired using a band saw or my table saw, square them up against the fence of the joiner and then tape the board to keep them from moving.  I then run both sides through the jointer so they’re straight.  They don’t need to be parallel.  This keeps the ends I’m going to cut flush when they’re put into the shooting board (the second photo).

Squaring Edges Shooting Board Jointer Plane Candling

The power jointer creates a long straight cut but it’s not as smooth as it could be.  The spinning blades create tiny gaps which just aren’t good enough for luthiery.  I use a long Lie-Nielsen jointing plane to clean up the cut from the jointer.  I try to get it ready for joining using as few passes as possible since you can run out of wood pretty quickly.  Also, the more passes I make the more “wavy” the edge begins to get–the blade of the plane takes varying amounts of wood as the grain of the piece changes direction along the joint.  If I can’t get it right in three passes with the Lie-Nielsen I put it back on the power jointer and start over again.  The power jointer takes off 1/64″ per pass.

The fourth photo shows me “candling” the joint i.e., holding the joint up to a light source to look for gaps.  It works really well.  A joint can look absolutely perfect until you hold it up to a window or bright light (or candle) and a .001″ gap shows up.  If the joint here is really tight the likelihood of the joint failing is really small.  After the glue dries the joint is stronger than the surrounding wood.

Joining jig Glue up Glue Cleanup laying protecting newspaper strip Tapping in Wedges

The jig I use for gluing is really simple and came from Cumpiano’s design shop.  I put the dry pieces in place, slide a piece of newspaper underneath (important) clamp little blocks of wood in place on the side using c-clamps and then glue the side using Titebond.  I then push the sides together, clean up the squeeze-out and lay another strip of newspaper on top.  Over that goes a heavy straight-edge and then sand bags to keep the joint from popping up when clamped.  I use little wedges I made from some ebony scrap and gently tap them between the side and the blocks.  Not a lot of force is needed. 

After an hour or so (if I’m gluing more than one set and need the jig) I’ll remove the wood from the jig and set aside to dry overnight.  I always undo the clamps before I remove the weight to keep the thing from popping in the middle and making me swear a lot.

One of the luxuries of working by myself is that when I make a mistake I can swear and no one can hear me.  When I was learning carpentry back in the mid 80s I was working with a friend of mine who had been in the business for 15 years.  I goofed up something and said an expletive.  He said, “Shhh!  Don’t swear!”  I was surprised by his prurience and asked him why.  He told me that if you don’t swear the client won’t know you’ve screwed up. That was pretty good advice. No one wants to hear their heart surgeon say, “damn!”

Anyway, these photos show the top being joined but the back is identical.

The next step is thicknessing which I do on a drum sander.  I’m going on vacation for a week so it may be a few days before my next update.   If you have any questions feel free to post them or email me.

2 Responses to “Joining the Back and Top”

  1. 1 Cliff Outlaw

    Hello Mr. Naugler. I’m in the process of shooting my first guitar top and have ran into a problem that I don’t quite understand. Here is my situation.. after have made several passes (shooting) with my plane, the double-curls appears. Once the curls appears, I take two more passes. At this point, the plates are now ready for candling. Holding the plates together I observe that the ends are not flush and the plate appears to have buckled. Do you hand any idea what I doing wrong? My preparation procedures are very similar to one mention in your article (Joining the back and top).

  2. 2 Seth

    Hi Cliff.

    It sounds to me like you’re following someone’s outline either from a book or a DVD but I’m not sure whose. You talk about “double-curls” which I’ve never heard of. You also say the “plates appear to have buckled.” I’m not sure what you mean by that, either. I’ll take a stab at what I think might be happening, though.

    In a nutshell, you’re overplaning. I count at least five passes with the plane before you start candling. From my experience less is more: if I haven’t gotten it right in five passes I often start over again, taking a 32nd of an inch off with the jointer and then putting it back in the shooting board for another try.

    The grain pattern in the joint is almost never perfect and the “runout,” or the direction of the grain relative to the joint, changes slightly as you move from top to bottom. Even with a huge jointing plane the blade will take a slightly larger “bite” if the grain runout is moving away from the joint (and planer) than it is if it’s moving the other direction. This gets compounded every time you take a pass with the plane.

    The power jointer makes a long, true joint but it’s not perfectly smooth because of the nature of the spinning blades. The jointing plane and shooting board fixes this but you have to get it right with one, two or three passes, generally. You can remove a high spot by making a partial pass with the plane and then a full pass to smooth it out again but this is sort of hit and miss.

    If the gap is always at the ends you might be pressuring the plane incorrectly. As you start the stroke you want pressure on the front of the plane (the frog) and none on the rear and as you finish you want all the pressure on the rear of the plane. If you’re not using a long jointer this is hard. A jointer is long just for that reason: to allow enough contact at the beginning and end of the stroke to allow the bottom of the plane to stay on the same “plane” as the joint.

    I hope this helps. (I hope it also makes sense. Runout is hard to understand without a diagram.)

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