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Neck reset on old Airline Arch top Acoustic guitar

   Hi, I have an old arch top airline guitar that needs repair. It has a loose neck. How do you remove the neck and does it have a truss rod? Also do you know where I can get parts for this guitar? The pick guard is broken and bridge is missing. I bought an adjustable bridge for it but it does not look like the pictures I have seen. I am trying to restore this for my sister and would appreciate any help.

Thanks Liz

   The joint between the body and neck is a dovetail. It is difficult to cut a dovetail joint that fits, and if you set your cutters to make a perfect joint it loses perfection as the cutter dulls etc. So, in practicality, the joint can be too tight or too loose. Martin made their dovetails too tight and then hand shaved them until they fit perfectly.  Harmony and Kay, the makers of Airline, cut their dovetails too loose and then filled the gap with hide glue. Somewhere between a few months and a few decades, the glue would fail and the heel would pop back leaving about an 1/8" gap at the bottom of the heel. I presume that the glue joint between the top and underside of the fingerboard is fine.

   First, close the gap. Make a caul to protect the heel and then use a long clamp across the back from heel to butt. With the gap closed, run a straight edge along the top of the frets to the bridge. The straight edge should touch the bridge about 1/8" from the top. If the contact point is below that, you will need to reset the neck. Let's presume that you don't have to reset the neck.

   It is possible to take the neck off (using steam), shim the dovetail until it is too tight and then shave it until it fits perfectly. But, the normal way to fix these is to fill them with glue and bolt them closed. Fit a 2" screw through the hole in a strap button, and drill through the heel about a 1/2" from the bottom of the heel, and into the neck block inside the guitar. You can use the screw as a clamp or you can use your long clamp and caul and drill it after it dries. Everybody needs a strap button. If it already has one, drill through the old hole, redirecting as necessary to get a firm grip in the neck block. Always remember to dry clamp to make sure everything fits.

   If there is a truss rod cover, there should be a truss rod underneath.  If there is nothing on the peghead or if there is a truss rod cover that says "Steel Reinforced Neck" you have no truss rod. If you have a rod chances are fair that it is broken. Sight down the edge of the fingerboard.  If the board is cupped, tighten the truss rod. The cupping should flatten out.

   Any arch top guitar bridge will work fine. Kay went out of business in 1968, Harmony went out of business in 1973. There are people with hoards of original parts. Go that route if you care a lot. Modern parts are mostly exact copies of Gibson parts, and they work fine. The feet must be fit to the top of the guitar. To figure the rough position of the bridge, measure from the nut to the center of the 12th fret, double it and add 3/32". Put sticky backed 150 grit sand paper on the top under where the bridge goes.  rub the bridge back and forth until the feet fit perfectly. It is very easy to rock, and round the bottom of the feet as you sand. Stewart MacDonald makes a tricky machine that stabilizes the bridge with a nylon roller. You can also get close and then scrape the feet flat.

   When the feet fit, you must make the string notches in the top of the bridge. Align the bridge top so that the shortest string is the small E string. The longest strings are the B and the big E, and the other strings taper from the small E to the big E. Hold a piece of string or thread in the E nut notch at the peghead end 1/8" from the fingerboard edge and up across the bridge. Mark this point with a pencil. Do the same for the other E. Now use a divider to mark the other 4 string positions on the bridge top. Gauged files are the best for making the string slots, but a sharp knife will work. Find a new pick guard if you must. Most people just take them off and play without one.

   When you get the above work all done, you will still need an action set to level the fret tops and adjust the string height. Before you start, sit and stare at the project for a long time. Understand how the parts work together. Imagine what can go wrong. I will often think about a project for days before I take up the knife. Airline archtops were almost valueless until Old Time players started using them a decade ago. 
Steve Mason

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