Fixing a Broken Button with a Clavette

Adding a clavette to a neck reset to fix a broken button is an efficient less invasive way to fix a broken button. This article will outline how to pick and align the wood for a clavette, how to fit the clavette, and how to reglue the button.

Required Tools

  • Lamp
  • Pencil
  • Razor edge straight edge
  • Rulers
  • Block plane
  • Upper block closing clamp
  • Small chisel (2.75 mm wide) with a 15 degree bevel on the sides
  • Strong hide glue
  • Various knives
  • Japanese pull saw with a small kerf
  • English dovetail saw with a small kerf

Why use a clavette?

The button is a weak point on every instrument. It doesn’t take much force for a button to give out. For a player this can be traumatic, but from a restorer’s view there are many worse things that can happen to an instrument. A clavette is a good alternative to reinforcing the button with a patch. It is less invasive because the top of the instrument is not being removed, the upper block is not being removed, the ribs are not being altered, and original wood is not being removed from the back to create a patch. The clavette is a strong reliable repair.

Step 1:

The first step before beginning the repair is to document as much of the neck set as possible. Since the neck has fallen out of the mortice, many numbers will be off. Getting any information will be very helpful when it comes time to reset the neck. Taking many pictures of the instrument before any work has been done is also advisable.

Saw out the neck. There is no need to saw off the button area, since the player did that for you. Instead, use water on paper towel squares to slowly remove the button form the beck heel. This must be done with care, especially if it is a joined button. Take the time to diligently remove the button rather than creating more work by breaking the button.

After the button is removed from the neck, set the neck aside and clean up the mortice. You don’t need to be too thorough just remove big chunks of glue and make the area where the clavette will be fit is free of debris.

Fit the Button

Initially fit the button to the back, sometimes it will be a clean split, sometimes it will be difficult do get the button back into place. This is the time to make sure the button will fit. Check the fit in the same way you would level a crack. Make sure the button is level in relation to the back and that it fits into place well. If it does not do this make the appropriate changes to get it to fit; this can be coaxing maple fibers back into place or removing some wood to get the button to lie level. Maple is a tricky material due to the way the grain grows. Sometimes to get the button to blend with the back is to remove some of those fibers that cause a nuissance.  

Excavate the clavette mortice

Now it’s time to make the mortice for the clavette. The mortice needs to be an even height and depth. The height is determined by the thickness of the chisel used. Try and use the smallest chisel possible. For this clavette a 2.5 mm chisel with the sides beveled at 15 degree was used. 

The depth of the clavette mortice is determined by where the purfling is on the instrument as well as the depth of the block. The mortice needs to be deeper than the purfling but not extend all the way through the block. To check the block depth, send a skinny stick through the end button of the instruments until it hits the upper block, then make a pencil mark on the stick. Take the stick out of the instrument and line the pencil mark with the end button and see where the stick ends in relation to the upper block. This is a rough estimate of the block depth. A hacklinger gauge may also be used but if the block is too thick it will not register.

Now that the depth and width of the mortice has been discussed, it’s time to cut the mortice. Score a line at the height of the mortice and then start excavating to the desired depth. Do not worry about extending the mortice all the way to the walls of the neck mortice.

When the desired depth of the mortice is achieved, now extend the sides to the wall of neck mortice. This where having the bevel on the sides of the chisel is handy. Having the clavette fit at a dovetail makes the neck set and neck shaping much easier later on.

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