Boesy Capo Problem

[hgreeley at sonic.net]

Hi,

The age of the instrument will matter, as well.  These bolts were not
necessarily standardized for a long time.  Getting new bolts and nuts
might be a good idea.

Bosendorfer used to have a fairly well documented procedure for these
kinds of repairs (guess they needed it).  If you cannot find it elsewhere,
I'll see what I might be able to dig up, though it would take a bit.

Hope this is of some help.

Best regards.

Horace


> David,
>     It's better that the nuts appear to be the problem not the bolts. But
> still,  you state " Apparently in the rebuilding of this, the threads on
> both bolt and nut  were compromised" This is worrisome considering the
> stresses they will be under when brought to pitch.
> You asked, "That being said (forgive my machinist ignorance) can you not
> simply cut the threads on the bolt to a slightly smaller size and replace
> the nuts with something appropriate."
> Answer, yes you can, but when you reduce your bolt to a slightly smaller
> size and replace the nuts, you reduce it's strength to the strength of the
> new size. For example if a 5/16ths 18 bolt (5/16ths being the diameter, 18
> being threads per inch) is stripped and one reduces the diameter slightly
> and re threads it to a 1/4 20, your newly threaded bolt will only be as
> strong as a 1/4 20 bolt not the original 5/16ths 18. So you will lose some
> strength, whether it be enough to be an issue is dependent upon how much
> of
> a safety factor was engineered into the application.
> The device you want is called a thread pitch gauge, this will tell you the
> threads per inch, the threads per inch and diameter of the stud will tell
> you what it is, 1/4 20, 5/16ths 18, whatever, in this case I would guess
> that we are dealing with a metric size.
> You stated the decimal size was about 0.268, if that is correct you
> probably
> have about a  7mm diameter (slightly stripped 7mm), the thread pitch can
> be
> fine or coarse. You could go down to a 6mm, but again, who would know if
> it
> will be okay, not me.   Good luck,   Mike
>
> ----- Original Message -----
> From: "David Love" <davidlovepianos at comcast.net>
> To: "'Pianotech List'" <pianotech at ptg.org>
> Sent: Friday, December 14, 2007 12:16 PM
> Subject: RE: Boesy Capo Problem
>
>
>> It does appear that the threads are more of a problem on the nuts than
>> the
>> bolts so I might get away with it.  I'd like to avoid replacing the
>> bolts
>> if
>> possible as not only do they have to fit the plate but they are bent at
>> rather strange angles in order to align with the capo bar.
>>
>> That being said (forgive my machinist ignorance) can you not simply cut
>> the
>> threads on the bolt to a slightly smaller size and replace the nuts with
>> something appropriate.  Also, what is the gauge called that you use to
>> measure the thread counter per...?
>>
>> David Love
>> davidlovepianos at comcast.net
>> www.davidlovepianos.com
>>
>> -----Original Message-----
>> From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On
>> Behalf
>> Of MICHAEL MORVAN
>> Sent: Friday, December 14, 2007 8:23 AM
>> To: Pianotech List
>> Subject: Re: Boesy Capo Problem
>>
>> David,
>>    Referring back to my machinist days I can suggest/explain the
>> following.
>> 1. If the threads were simply ripped/stripped out of the "nut", and the
>> threads on the "stud/bolt" are still intact, you can "chase" the threads
>> on
>> the stud with the appropriate die to clean them up, and then replace the
>> nuts.  HOWEVER
>> 2. If the threads were ripped/stripped off the stud/bolt, you have a
>> problem, and will need to replace the studs and bolts. If you chase
>> threads
>> that are ripped off a stud, you can get a nut to go on well but, there
>> won't
>>
>> be enough material left to hold the nut, and as soon as you put a load
>> on
>> it
>>
>> watch out, it will fail.
>> 3. For further information type "class of fit" in any search engine, and
>> you
>>
>> will find many articles referring to the relationship of nuts and bolts
>> concerning threads and strength.   Good Luck,    Mike
>>
>> Michael A. Morvan
>> Blackstone Valley Piano
>> Dedicated To Advancing The Art Of Keyboard Restoration
>> 76 Sutton Street
>> Uxbridge, Ma. 01569
>> (508) 278-9762
>> Keymaestro at verizon.net
>> www.pianoandorgankeys.com
>> www.thepianorebuilders.com
>> ----- Original Message -----
>> From: "David Love" <davidlovepianos at comcast.net>
>> To: "'Pianotech List'" <pianotech at ptg.org>
>> Sent: Friday, December 14, 2007 10:31 AM
>> Subject: Boesy Capo Problem
>>
>>
>>> Interesting problem.  1890's Boesy.  The heavy metal capo bar is held
>>> in
>>> place by several bolts running through it and held down by some cap
>>> nuts.
>>> Apparently in the rebuilding of this, the threads on both bolt and nut
>>> were
>>> compromised so that as the piano was being tuned the nuts let go and
>>> popped
>>> (probably shot) off.  So the bolts need to have the threads recut and
>>> the
>>> nuts replaced.  Not a big deal but I need some advice on re cutting the
>>> threads.  The outer dimension of the bolts is .268".  Can anyone
>>> suggest
>>> the
>>> best approach for this, tools, thread count, etc..  Machining type work
>>> is
>>> not exactly my area.  BTW  I'll have to send some photos of the bass
>>> stringing (eastern European rebuilding job).  You won't believe it.
>>>
>>> David Love
>>> davidlovepianos at comcast.net
>>> www.davidlovepianos.com
>>>
>>>
>>>
>>>
>>
>>
>>
>>
>>
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