Grafting a New Neck

triangle strings | technique article | woodworking | instrument repair | violin repair | restoration | final graft | setting | luthier

Author: Dustin Fagg

A neck graft is often necessary after a break in the neck, or as frequently occurs in cellos, a break at the neck heel. A neck graft may also be necessary to correct neck measurements, a poorly executed graft, or to modernize a baroque setup. This procedure involves removing any remaining neck pieces from the body of the instrument, preparing the original scroll and pegbox, fitting a new neck to the peg box, and setting the neck into the body of the instrument. In this article I will cover everything but setting the neck into the body, which can be found in our previous neck resetting technique articles.

Tools required

Tools

Removing the Leftover neck and neck Heel

First check that all the seams are closed, attempting to remove the neck heel on an instrument with open seams can result in rib cracks. Being careful to not cut into the ribs or button, use a saw to remove the majority of the waste material. After sawing you’ll be left with the last bit of the neck heel in the neck mortise. I use an in-cannel gouge to split out this material. Use your fingers as a stop to keep the in-cannel gouge blade under control. After placing the in-cannel gouge where you would like to make your cut, strike the back of the gouge with a hammer and the pieces should pop out as they split. Soak a small piece of paper towel with water and place it on the last bit of neck root that remains attached to the button; after soaking for some time the sliver of neck root should peel off.

Preparing the counter form for the scroll

Make a counter-form for the scroll with dental compound and plywood. Trace the general curve of the back of the scroll onto the plywood and cut it out with your favorite band saw. Heat some dental compound in hot water and apply it to the surface of the plywood that will touch the back of the scroll. Place Saran wrap over the dental compound to protect the varnish and press the scroll into the counter-form. I like to leave the excess wood on the sides of the counter-form until after I have sawn out the graft relief from the scroll. Leaving the counter-form square allows convenient clamping in your bench’s tail vice.

Cutting the scroll to RECEIVE the GRAFT

The next step is to cut the pegbox to prepare for the graft. These cuts should be angled in from the neck toward the volute, and in toward the bottom of the pegbox to allow for ease of fitting the new wood. Using a scarf joint in this manner facilitates the constant and efficient adjustment of the mating surfaces with planes and chisels for a perfect joint. Your saw kerf should end around the middle of the treble peg (A for cello and viola, E for violin, G for bass). Check on the progress of your cuts with a ruler inserted in the saw kerf to ensure you are cutting at the correct angle relative to the future neck plane. Once you are happy with your cuts in the cheeks, make a final kerf in the duck butt connecting the bottom of the two previous saw cuts. When these cuts are complete, use a hammer and a sharpened feeler gauge to split out the remaining wood. Check the split of the peg box beforehand to ensure that splitting will be safe. Consider a different method of removal if the grain of the pegbox is particularly run-out. Note that the angle of the business end of the feeler gauge should be oriented so that if it grabs and cuts into the peg box, it will do so up and away from the back of the scroll. Be sure to support the volute while hammering as it is very weak along the grain at the throat and will split off if not supported.

CLeaning up the saw cuts

With the initial cuts complete, clean up the gluing surfaces of the peg box with a freshly sharpened chisel. While progressing, check and confirm the flatness of the surfaces with a knife edge straight edge, they must be flat before moving on.  A good tip is to leave a small sliver of wood in the angle channel where the cuts meet to avoid digging your chisel into the peg box. This “small sliver” can be removed with one cut at the end, leaving you with a nice clean angle channel before fitting.  The back of the neck graft surface should also be angled slightly upwards in comparison to the eventual fingerboard gluing surface. This angle allows for the graft to be “wedge” shaped so as fitting progresses the graft lifts higher out of the pegbox.

Preparing the graft wood

Next you’ll need to prepare the piece of graft wood that will be fitted into the peg box and become the new neck. Choose maple of similar appearance (i.e. similar figure – grain and wood properties) to the scroll while also taking into account the figure of the ribs.  As we begin laying out and fitting the graft wood it is important to consider how the scroll will line up with the body of the instrument. When complete, the new neck, volute, and pegbox, should align as a whole to the body of the instrument. This is tricky, and is a detail that is often missed, but helps set apart great work from good.

Moving forward, find and mark the center of the instrument as explained here.  Using this center mark, the center of the button, and the T bevel,  determine the fingerboard gluing plane relative to the plane of the body of the instrument. Use this determined angle recorded with the T bevel to ensure that the neck heel will hit the button when the scroll is in line with the instrument and all the measurements are exact.  If the projected result misses the button, refit to correct.

Flatten the neck surface where the fingerboard will be glued. Be sure that the grain of the graft wood is parallel to final fingerboard surface Be sure to take into account the angle of the neck heel when establishing the neck surface . Also take into account the final poirette when establishing the neck surface. Once the neck surface is done you can lay out the peg box portion of the graft wood. Use a piece of folded paper to get the angles of the cheek surface and lay that out on the center line of the graft wood. Add two millimeters to this  to allow for the increasing angle from the bottom to the top of the peg box graft surface. Then, allowing for the scroll clearance (1mm and 3mm for cello and .5mm and 1.5 mm for violin and viola) place a flexible ruler on the ramp of the peg box and pull the scroll away maintaining the ramp position and angle. Mark the bottom side  of the ruler and add 2 mm to that.

Using a template that represents typical neck length and neck root measurements conservatively mark out the first and last positions available by the duck butt. Using your band saw, cut away the excess wood until you have enough room to fit the block plane on the back of the graft wood.

Fitting the graft wood to the peg box

You now have your rough cut graft wood ready to go. Plane the back (relative to the body of the instrument) surface of the graft wood first. This is the part of the graft that will contact the ramp. Check the back angle to the body of the instrument to be sure that the scroll will be in line with it. To do this, place the scroll on the graft wood, holding the ramp and the back of the graft piece together, and lining the graft up with the button of the instrument. This will show you how the scroll hangs with the body of the instrument. Once you are happy with the back surface and how it makes the scroll line up with the body of the instrument you can prepare the sides of the graft wood with a block plane. When the graft wood is fit it should not have any gaps.

When holding the scroll on the graft, wiggle and twist it this way and that to see if it moves around at all. If the scroll wiggles on the graft one or more gluing surfaces are not aligned or flush. The graft piece may also make apparent any inconsistency in the scroll portion of the graft. You can go back and fix those surfaces if necessary. Exclusively use a very sharp chisel to clean up the peg box and your life will be easy-peasy lemon squeazey. Avoid using sanding blocks and chalk for fitting as it will give you false readings and you’ll be chasing gaps and wobbles endlessly.

A note on fitting, though it may be tempting to have the cheeks of the scroll hollow to make the fit appear gapless, don’t hollow the cheeks. Once the glue is done drying you may find that the unseen gap has been closed by the glue leaving the outside of the pegbox hollow or concave.

Now that the graft and the peg box are fit mark the position of the nut on the graft wood. This will be used as a reference when gluing the graft and offer peace of mind.

Preparing the graft for gluing

Make some fresh hide glue for the neck graft as it deserves fresh glue! Be sure that the counter forms for the cheeks of the graft are flat and free of texture. Any texture on the counter forms will end up in the varnish of the peg box. Prepare the back of the counter form so that it is parallel with the neck surface of the graft wood. Lastly do a dry clamp run and draw a line where the neck surface meets the nut portion of the peg box. This line will show you if the peg box is sitting in the right place when it is glued. You may not get the peg box all the way down on the graft wood and that’s okay up to a half millimeter or so. Be sure to clean up any hide glue that squeezes out of the joint. After cleaning up the excess glue, run a bead of hide glue all around the seam to ensure that the outermost portions of the joint don’t dry before the innermost portion

Finishing the pegbox

Once the graft has dried for 24 hours carve out the peg box. Maintain the measurements of the back and sides of the peg box as you carve away the waste wood. Maintain the original nut placement.

Once the graft has been completed the rest of the job is treated as a typical neck set or reset. Having the neck reset procedure in mind is important and if you haven’t done one before I recommend referencing our series on resetting a neck before carrying out a neck graft.