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"How To" Manufacture Kerfing
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Kerfing is one of the ways we join the sides of a guitar with the top or back, the main purpose of kerfing is to create a larger gluing surface to create stability to the glued joint. The shape / size / thickness can affect the way a top or back vibrates.

Kerfing in general is made from a hardwood, typically Maple, Mahogany, Basswood or any other form of hardwood.

You can use softwoods for kerfing but it is not a general practice.

Time to manufacture approx 1 hr
Some bits of the broken kerfing in the guitar, you could clean it up and re-use it, however it is much easier and neater to simply make some more.
I first need to match the wood colouring, its clearly Mahogany, I have some scrap African Mahogany which is very close in colour.
The width of the original kerfing is 14.36mm
The spacing between the kerf cuts is approx 6mm.
Total thickness of 5.34mm
Side view of the old kerfing
I first set my table saw up to match the angle of the kerfing, we do this by simply rotating the blade until it touches across the whole width.
Out of curiosity it happens to be 20 degrees
You can see in this photo, the kerfing is used to join the sides to the top.
It is also used to join the sides to the back.

This Martin has taken a big hit from poor shipping. The back is shattered, the braces are broken and some of the kerfing has been destroyed, its had numerous previous repairs by all the exposed glue.
You can also buy kerfing from most musical instrument parts suppliers.
Using the band saw, I do my first cut to have a workable piece of wood.