Upright pressure bar

[Warren Fisher]

(Comments interspersed)
Lance Lafargue wrote:
> 
> I saw a piano today that had been restring by a PTI (piano technician
> impersonator).  One of  MANY problems was the pressure bar not being
> tightened down enough and the strings were then badly spaced.  I could
> squeeze the unisons with my fingers and easily move them around.
> QUESTION(S):
> 1)Should I lower the tension (it's 80 cents flat) then tighten the pressure
> bar, or can I tighten it without lowering tension?

Lance, If it is just a small area that is slipping, I would put protec
on the screw head and use a large screwdriver with a visegrip attached
as a "turner handle" to back out the screw a quarter turn, then go back
slightly tighter than it was originally.  You have to realize that the
tension of the string at 80 cents flat is contributing to the problem.
Possibly, if you just raised the string to pitch, it wouldn't move on
you.

> 2)How should I decide how tight is tight enough when I don't have a clue
> where it was originally?  (How much angle do I need?)

Use a dial caliper to measure pressure bar height.  Open the jaws about
one inch and insert the wire, that sticks out the end of the caliper,
down next to the bar until it touches the plate.  Then push the caliper
down until the end touches the top of the pressure bar.  Record the dial
reading and the location on a diagram in your breakdown notes.  Measure
several locations along the bar. By comparing the bad areas with the
ones that are working you can arrive at a usable bar height.  Also
measure the height of the V-bar to see if it is uniform.  It could be
lower in the bad areas.  

> 3)When restringing an old upright, how do you (ya'll in the south) measure
> it's original height before destringing?  Do you use a ruler or use wedges
> like measuring plate locations, or what??  I assume that you all remove it
> and replace it after restringing.

Yes, see above.

Hope this helps,

Warren


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Warren D. Fisher
fish@communique.net
Registered Piano Technician
Piano Technicians Guild
New Orleans Chapter 701