Does my bolt on neck need shims?

[Mottlefeeder]

... One thing that puzzles me is the fact that some basses used to come with a micro-tilt adjustment screw at the backplate. There was another plate inside the neck pocket, and this screw was adjusted against that plate to get the proper neck angle, then the neck bolts were tightened. In this case, only the tilt screw would be making contact in the pocket, instead of the entire neck butt solidly joined. I would think this would really hurt sustain. After all, isn't that the main reason for neck-thru-body construction? Sustain? ...

I have heard of this design, but never met one. Is it possible that this type of bass was not renowned for its sustain anyway?

 

[blipndub]

Old Peavy T-40's had this micro-tilt adjustment. it's quite common on Fender strats and teles. Maybe on three bolt Jazz basses?

 

[Ken FenderJazz]

Bolt the neck back on, taking care to snug up (don't overtighten!) the screws closest to the shim first. Then snug up the others. Finally go back over all the screws and make sure they are tight.

Mag...

Can anyblody tell me the definition of overtighten here? Seems like you want them good and snug for max sustain. But when are they too tight? Is there a torque spec?

Thanks
ken

 

[Magneto]

Can anyblody tell me the definition of overtighten here? Seems like you want them good and snug for max sustain. But when are they too tight? Is there a torque spec?

Thanks
ken

Sure, you want them very tight. And chances are, your screwdriver would slip on the phillips screw head before you torqued them tight enough to strip the threads in hard wood like maple.
What I was meaning was to not overtighten the first two screws at the shim side. You want to seat the neck at the shim first, then draw the other side's screws up tightly, but you don't want the shim-side screws so tight that you're pulling against them when you tighten the opposite side. Kinda like tightening up a flange.. If you tighten down one side too much without drawing up the opposite side, the bolts might all be tight, but the flange might not be seated properly..

Mag..

 

[Ken FenderJazz]

Haven't yet shimmed, hope to within a couple of days. But here's my question - why?

Why would this happen to a perfectly good neck - I would assume it came good from the factory. As I was walking up the stairs toward the computer, one thing popped into my mind - perhaps from sitting in a guitar stand for years?

I don't know, maybe I'm just completely nuts, but it seems there should be an explanation for a neck changing its characteristic so much.

What does anybody think, or do they?

ken

 

[gapupten]

The bass in discussion that started this thread was a late 80's Pedulla. Its is my belief that 15 or so years of compression from screws and string tension caused the wood of the body or neck at he pocket to compress slighlty. That is all that is need.
Hope that helps. Maybe someone else has a better view of the physics.

 

[BassyBill]

I found with my Rick that some buzz around the second to fifth frets was caused by backbow. Solved this by slackening off the truss rod to give a touch of neck relief (VERY slight forward bow). Now it's fine again.... aaaah...

BTW, I used a thin cardboard shim in my fretless to adjust neck tilt. No problem with sustain on this baby! Seems to me that under the sort of load experienced in a neck pocket (ie, between two surfaces tightly screwed together), a slightly compressible material, like cardboard, will actually go "hard" when it's been squeezed enough. Think of a spring squeezed until all its coils are touching. Some books and websites I've read on setup jobs actually recommend card as a shim material.