[pianotech] plate lags, (was persistent customer)

[Al Guecia/AlliedPianoCraft]

I'm with Ron on this one. The only time I check the plate bolts/screws is 
when I'm restringing a piano. I don't tighten all of them, I just check for 
any that may be loose, which I just snug up to match the others.

Al G

--------------------------------------------------
From: "Ron Nossaman" <rnossaman at cox.net>
Sent: Tuesday, December 30, 2008 8:02 AM
To: <pianotech at ptg.org>
Subject: Re: [pianotech] plate lags, (was persistent customer)

> Geoff Sykes wrote:
>> It's so easy to get into arguments on the list.
>
> This is about what's fact and what isn't.
>
>
>> Screws imbedded into metal rarely need tightening unless they are subject 
>> to
>> vibration. And even then the phenomena is rare. That's because metal 
>> changes
>> very little with changes in temperature or humidity.
>
> Right, which is why perimeter bolts in Baldwin and Yamaha grand don't move 
> when checked for tightness.
>
>>Wood, on the other
>> hand, can change quite dramatically with changes in temperature and
>> humidity. Why do you think a piano can go out of tune simply by turning 
>> on
>> some stage lights?
>
> Because the hot lights expand the strings, that's why. It's not wood 
> movement.
>
>
>>Over time, things like screws, nails etc., will be
>> effectively squeezed out. They get loose. They need to be tightened.
>
> I understand how they get loose. I'm questioning the "need" to tighten 
> them periodically when they'll just get loose again as more wood is 
> crushed. It seems to me that stability would be better served by letting 
> the system settle where it will after a first "service bond" type 
> procedure after manufacture, and reach equilibrium. Thirty years ago, I 
> tuned a lot of old uprights. Someone had mentioned to me that the washers 
> under the plate lag heads across the top were worth notice. If they could 
> be turned by hand (the washers, mind you, not the bolts) it was an 
> indication that the back was still solid. Many of these old pianos with 
> "loose" bolts were as stable as anything I've seen since.
>
> So the question remains. Why is it necessary to periodically tighten plate 
> bolts when there is no clear indication that tuning stability is enhanced 
> by the process, while there is every indication that increasing damage is 
> being done as a result of periodic tightening?
>
> Ron N
>
>