More Bridge Problems

I was having a lot of trouble intonating, and the I realized that the posts were coming up out of the body again. posted on strat-talk and ended up in an interesting thread, even getting a response from Ron Kirn. His advice was to rout out the body, and glue in a wood  block,  so that the posts would go in to the block.


For this to work, I'll need to know how to rout the body (apparently one uses a router bit), and it seems like I'd be ok with a 1/2 " diameter, 1" length bit.  There's a link to a source in the thread linked to above.  Today I traced the outline of the routed part of the back of the guitar, and made some measurements.  Here's my diagram:

So I need a block that's 2 1/4 x 3 1/4 x 1 1/2 inches.  Ron said I should use a hardwood like alder or ash, but the local lumberyard has only oak and poplar.  This launched me on a dangerous quest to understand wood hardness.   After killing a troll with a sword I found once I opened a chest with a key I got from a magical hen in exchange for an egg I'd stolen, I found out that wood hardness is measured using the Janka Hardness Test. This test measures the force (in pounds) required in order to embed an 11.28mm steel ball into a piece of the wood, to half the ball's diameter. Why they chose 11.28mm is still a mystery. There are many tables of values on the web, such as this one.

Some interesting values (some I had to find on other sites):

Ebony	3200
Mulberry	2820
Rosewood	2200
Mahogany	2200
Maple	1450
Ash	1320
Oak	1200
Alder	590
Poplar	540
Basswood	410
Paulownia	250-290
Balsa	100

So it seems I should go with oak.  I'm nervous about doing this, but I think I can do it. If I can find the time today, I'll go over to Mike's Lumber.