| Kenneth Michael Guitars est.1978 |
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| Fitting the neck to the body --- KMG Neck set --- PART #1 |
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| Although we are using a mortise and tenon joint (MT) in this example the principles covered also apply to the dovetail joint (DT). Specifics for dovetail trimming, shimming, etc. will not be covered at this site. Long ago, I was converted to the MT bolt-on method after being convinced and convincing myself that the hassles involved with the DT yielded nothing but the satisfaction of being able to do it. Others are sure to disagree. |
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| Installing / assembling the neck to the body is certainly one of the most important aspects of construction. I believe most have the tendency to begin the fitting process while the body and the neck are in the rough finish stages. The logic seems to be that we have to reconcile ourselves to the fact that the parts must be trimmed to get them to fit each other. So do it all at the same time. What is often over looked is the need to establish our dimensional and geometric base lines. In other words the neck and body must be prepared in such a way that we know, for example, that the top is 90 degrees to the rim at the neck location. If I learned anything over the years as a problem solving Engineer. It is the importance of “root cause analysis” and the discipline required to change only one variable at a time and to measure the result after changing something. To a large degree, fitting the neck to the guitar body falls into a similar realm of problem solving. The following details the things I have found to be crucial for an accurate expeditious neck to body fit operation. |
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| Make sure there is clearance at the end of the tenon. The tenon does not bottom against the neck block --- this space is used for adjustment. Also, if the neck is glued in place, the gap provides a space to inject steam to loosen the glue if a neck re-set is necessary. (A different article). |
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| The area where the neck meets the body must be dead flat. Use a flat sanding board to accomplish this, sanding top to bottom than side to side (with the grain) to remove scratches. |
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| The"top to rim" angle in the neck location must match your plans/ blue print --- mine and I believe Martin happens to be 90 degrees. At this point I recommend the adjustment be accomplished by sanding the rim. |
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| Trim the cheeks on the neck heel so that they are dished in towards the tenon (XXX) – leave about 1/8 to 3/32 untouched this is the surface that actually contacts the body. The neck manufacturer took great pains to get this angle correct so only change it as a last resort. KMG and Martin have the cheeks machined at 89 degrees.Note: that the (XXX) area extends all the way to the end of the heel. The heel cap will cover the slight taper that is created. |
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| Notice how the cheeks taper in toward the tenon creating a relief area. The magic here is, now you only have to contend with the outer portion of the heel to make perfect contact. There is no need to be concerned about making the entire end of the neck conform to the body. |
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| The simple analogy is like buying a set of tires for you car. The specification of the tires must match the specification of the car. Its not likely you would modify the car to make the tires work – you would first make sure they were compatible, and only the thing to worry about is the minor adjustment of balancing. A similar comparison holds true for the guitar body and neck --- I can draw a perfect guitar with my CAD program because the dimensions and angles are correct --- So if the dimensions and angles of the parts are correct they WILL match and fit properly. |
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| OK – now we are ready to fit the neck. Go to Part #2 |
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