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#623381 - 09/13/05 12:38 PM Tightening Plate Bolts
showard Offline
Full Member

Registered: 05/10/05
Posts: 141
Loc: Hortonville, Wisconsin
Is it possible to overtighten plate bolts? I recently purchased one of those plate tightening screw drivers that fits in the end of a tuning lever from Schaff. On a piano I was tuning, I tried to tighten the plate bolts with a regular screwdriver, but they wouldn't budge. When I put the new screwdriver on with the tuning lever, I was able to turn the bolts about a quarter turn. I possibly could have turned them further, but I was being cautious in case there was a chance they could be overtightened. Is this something I should be concerned about?
Steve Howard
Piano Technician
Owner of Howard Piano Industries

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#623382 - 09/13/05 03:47 PM Re: Tightening Plate Bolts
bellspiano Offline
500 Post Club Member

Registered: 05/25/04
Posts: 820
Loc: Boston, MA
Hi, Steve --

Why are you tightening the plate bolts as part of a tuning? Is there some difficulty you are trying to remediate?

I ask because I was taught to leave the plate bolts alone. My understanding is that if the bolts are tightened too much, the plate can crack, and then the creature is not a piano any more. I could be wrong.
Dorrie Bell
retired piano technician
Boston, MA

#623383 - 09/13/05 03:56 PM Re: Tightening Plate Bolts
Grandpianoman Offline
2000 Post Club Member

Registered: 03/12/05
Posts: 2726
Loc: Portland, Oregon
I am not a piano tech, but I found out from talking with some piano rebuilders that tightening plate bolts on pianos that are pulled up to pitch is not a good idea. I had an older grand piano and noticed that the plate bolts were not tight. Evidently, if you overtighten them, you can crack the plate due to the stress each bolt puts on the plate while it's under all that tension. When the strings are off, then you can tighten the bolts without worrying about cracking the plate. I think it also changes the downbearing, which can change the tone of the whole piano and can also ruin the sustain?...... Maybe a tech person can add to this.


#623384 - 09/13/05 09:27 PM Re: Tightening Plate Bolts
Ron Alexander Offline
1000 Post Club Member

Registered: 06/17/03
Posts: 1292
Loc: North Carolina
Good question, "Why are you tightening the screws as a part of tuning?" The plate is cast iron and can be cracked if you tighten to much....recommendation leave them alone unless there is some reason to suspect a problem..then get an expert opinion if need be...
Ron Alexander
Piano Tuner-Technician

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#623385 - 09/14/05 01:13 AM Re: Tightening Plate Bolts
Dale Fox Offline
1000 Post Club Member

Registered: 10/17/04
Posts: 1203
Loc: Nor California Sacramento area
If it's obviously loose, tighten it gently. Otherwise leave them alone. Many pianos have a dowel on each side of the plate bolts (Steinway style system)which is glued into a hole to provide support for the plate and keep it off the sound board. The large rim screws can easily be tightened enough to break loose the glue joints on these dowel mounted systems. There's way too much tightening goin' on out there!

The cast iron is the least of the worries here.

Dale Fox
Registered Piano Technician

#623386 - 09/14/05 01:33 AM Re: Tightening Plate Bolts
Keith Roberts Offline
2000 Post Club Member

Registered: 05/04/04
Posts: 2002
Loc: Murphys, Ca
I see if I can tighten them with a regular screw driver. If they move I snug them with the hammer and blade so I don't mar up the screw slots. After the second million or so screws and bolts I have put in, it becomes second nature to use the wrench that gives the best feel and I can tell by feel when a bolts going to snap or strip. I guess you call it 40+ years of fixing things. I error on the side of caution. If you are just checking things, use a small wrench, if you have to move it, get out the right size tool. A 12 inch long handle on a screwdriver will break just about any screw I know.
Keith Roberts
Keith's Piano Service
Hathaway Pines,Ca

#623387 - 09/14/05 01:47 AM Re: Tightening Plate Bolts
velopresto Offline
500 Post Club Member

Registered: 05/05/04
Posts: 605
Loc: Santa Clara, CA
I tighten--but don't overtighten--the plate screws on most of the pianos I tune. Some of them are already so tight, I leave them alone. The ones you are certainly never supposed to touch are on Baldwin grands that use accu-just hitch pins.

I've been taught by several technicians that snug plate bolts help in tuning stability. I certainly don't do it every time, but I do it the first time I service a piano.

I have never stripped a screw hole, but I HAVE found broken bolts, and many that had stripped their holes...all new pianos!

Interesting that this subject pops up now, on a day when I serviced a new piano where not one, but THREE plate screw holes were stripped. This piano needs help, and I'm awaiting word from the manufacturer as to what to do about it.
Dave Stahl
Dave Stahl Piano Service
Santa Clara, CA
Serving most of the greater SF Bay Area

#623388 - 09/14/05 08:56 AM Re: Tightening Plate Bolts
showard Offline
Full Member

Registered: 05/10/05
Posts: 141
Loc: Hortonville, Wisconsin
The reason I even thought to try and tighten them was that I had read some comments from several techs off of the PTG forum that they check the tightness of the plate bolts on every piano that they tune. It appears that these can be overtightened and only tighten the bolts as much as a regular screwdriver would allow.
Steve Howard
Piano Technician
Owner of Howard Piano Industries

#623389 - 09/14/05 10:05 AM Re: Tightening Plate Bolts
vin mrykalo Offline
Full Member

Registered: 03/23/04
Posts: 53
Loc: Kansas
It's a good idea to check the plate bolts to make sure they're tight before tuning, especially if it's the first time you have seen the piano. Seems to me that you may have a greater chance of breaking a plate if they are too loose. On pianos that I regularly service, I check them every two or three years. Rule of thumb is don't tighten them more than 1/4 of a turn at a time. (Yes they can get that loose).
Vince Mrykalo RPT MPT
UK Piano Technician


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