Plate - Grinding

[Alan W Deverell]

Peter & Others - I might have added (although most may already know):

1) Cast Iron is quite brittle - surface defects in stress areas can
lead to fracture cracks - can lead to eventual breaking of the
casting.

2) Cast Irons is NOT very ductile - do NOT hammer or subject to high
impact/shock loadings (drop on to a concrete floor). There is an
exception to this, in that, "peening" a welded crack to unify the
stresses introduced by welding - but this is the preserve of a skilled
cast iron welder).

3) If you progressively "drill out" a line along the 25mm you wish to
remove (as someone suggested) you MUST ensure that you grind away the
drillings so as to ensure a clean uniform blended (fettled) surface
conforming to the sculpture of a GOOD plate design, otherwise, if the
are any loadings throughout the area removed then the caution of "1)"
above may be revealed.

4) Some Piano Castings are pretty rough and "fettling" of the castings
not properly undertaken. I believe that tidying up with a die-grinder
etc. (as described below) is often appropriate/essential to a
professional re-build before the plate is re-painted.

5) The invasion of Cast Iron dust included the human skin etc., so, if
face, scalp, hair and hands etc. are not covered then you will
certainly require to take a shower otherwise you may look like Al
Johnson, or some other character out of the Black & White Minstrels.

AlanD (who has often looked like Al Johnson but never sung like him)

PS - Not sure if Belgium knows about Al Johnson and the "Black & White
Minstrels"

>-----Original Message-----
>From: owner-pianotech@ptg.org
>[mailto:owner-pianotech@ptg.org]On Behalf
>Of Peter Kestens
>Sent: Sunday, August 23, 1998 7:17 AM
>To: pianotech@ptg.org
>Subject: Re: Plate - Grinding
>
>
>Alan,
>
>Thanks a lot for your information.  I hope it all will work well.
>Peter
>-----Oorspronkelijk bericht-----
>Van: Alan W Deverell <aland@casa.co.nz>
>Aan: pianotech@ptg.org <pianotech@ptg.org>
>Datum: vrijdag 21 augustus 1998 1:37
>Onderwerp: RE: Plate - Grinding
>
>
>>Although I have never had to remove as much as 25mm (1"), my work on
>>Older Cast Iron Plates has all been done with the aid of
>the following
>>equipment:
>>
>>1) Tool Makers Die Grinders (electric or pneumatic) fitted with
>>appropriate "Mounted Points" up to 1" diameter and shaped, using
>>"dressing tools" to suit the "re-fettling" job.
>>2) Angle Grinders (electric or pneumatic) fitted with
>appropriate grit
>>disks and sanding pads.
>>3) Sanding "bobs" (mounted in electric or pneumatic drills) to level
>>some of the surface markings.
>>4) Hand sanding using cloth backed "emmery paper" strips.
>>
>>Any good engineering supply shop should be able to advise you in the
>>selection of all the gear.
>>
>>I recommend that you practice the skills on something unimportant
>>before you begin in earnest and that you ensure that the
>25mm you wish
>>to remove is NOT going to compromise the structural integrity of the
>>plate.
>>
>>Warning - Cast Iron DUST, produced by these methods, is
>VERY invasive
>>and it is essential to wear appropriate breathing apparatus, safety
>>glasses and ear muffs etc. and to vacuums clean/sweep up afterwards.
>>
>>AlanD (who learned these basic skills, 25 years ago, porting and
>>polishing the cylinder heads of racing engines)
>>
>>>-----Original Message-----
>>>From: owner-pianotech@ptg.org
>>>[mailto:owner-pianotech@ptg.org]On Behalf
>>>Of Peter Kestens
>>>Sent: Friday, August 21, 1998 8:12 AM
>>>To: pianotech@ptg.org
>>>Subject: plate
>>>
>>>
>>>Hello,
>>>
>>>I'm "truying" to rebuild an old (ugly) german piano to a
>>>(less or more)
>>>decent one.  Lets say  I do it  as an exercise.
>>>For this, I've rescaled the old stringscale but I've also to
>>>make a totally
>>>new bridge because the program (=Parsons) showed strings
>>>that are about 30
>>>mm to long (and this means inharmonicity is very bad). I
>>>also have to remove
>>>some metal from the plate: the new bridge comes about where
>>>two screws now
>>>fasten the plate.  There is place to make new screw-holes 25
>>>mm higher but
>>>what is the most easy way to remove about 25 mm of metal
>>>without to much
>>>damaging  the plate.   The screw-holes are for the moment
>>>left and right
>>>from the treble bar from the plate.  Thanks a lot for your help.
>>>
>>>Peter
>>>
>>>KESTENS.P@DEBCOM.BE