At 05:29 03/07/2017, Ray Lurie wrote:

 >I have a Zuckerman concert double from around 1971 with plastic jacks,
 >and they're still going strong--no bending, , no cracking, no problems
 >whatsoever. Â In the roughly dozen years I've had the instrument,
 >they've never been a problem and, over that time, I've had only a
 >single plectrum and two strings that I needed to replace. Â Unlike
 >wooden jacks, there's no need for seasonal readjustment of jack height
 >to account for expansion and contraction of the wood.

This is a new one on me.  Wood expands across the 
grain, which would mean horizontally in the case 
of a jack.  Furthermore the type of wood used for 
jacks is in my experience more than sufficiently 
stable in the vertical direction in all humidities.

However, for those who like to be ahead of the 
curve (warp?) I am waiting for some up to date 
builder to make jacks with integral plectra using an aunthenicke 3-D printer!

:)

David 

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