center pinning question - answered?

[Allen Wright]

Rafael,

I don't think my technique or approach to pinning is the problem. I'm  
using the right tools, I've been doing this work for a long time, and  
am careful in my approach. I'm well aware of the pitfalls you  
mention. The original Hamburg pins, although cut on both ends, were  
done very neatly, and I don't think they're tearing the cloth much,  
if at all, when they're removed - although I agree that can be a  
problem if one isn't careful.

Today I looked very carefully at quite a few of the original pins and  
compared them with the new ones. On average the original pins had  
12-15 swings, and registered 0 - 1 gram resistance. The new pins  
(exact same dimension, or if anything sometimes a hair smaller)  
create 3-4 grams resistance and 6-7 swings. (This is after working  
the flange a bit to compact them a bit with the new pin).

I carefully mic'd just the ends of many of the old pins and found  
them to be a half-thousandth smaller (50.5 rather than 51). So my  
operating theory at this point (until someone convinces me I'm wrong)  
is that indeed (as my shop mate - and also Wim Blees in an earlier  
post - suggested) the pins themselves have worn slightly. At first  
this seems unlikely; but then again, after 70+ years of wear, perhaps  
it's not surprising that some wear would take place due to the  
friction from the bushing cloth turning hundreds of thousands of times?

I've saved some of the pins, and will try and find a microscope to  
look at them with. Perhaps someone else out there has already thought  
this through. I'd be interested to hear.

Sincerely,

Allen Wright, RPT
London, UK

On May 16, 2008, at 4:47 AM, Rafael M. Huberman Muñiz wrote:

> Allen,
>
> I think that the problem is with something in your repinning  
> technique. Either is your device for pushing the old pin out  
> (punch, pliers, etc.) or the way you push the new one in, or the  
> things you do in between.
> The first one: you have to be very careful when you push the pin  
> out. The first thing is to note if the old pin has rough edges (one  
> or both of them) due to technicians that cut both sides of the pin  
> after inserting it or, worse than this, technicians who file the  
> end of the pins so you don't see the rough cut but a smooth  
> surface. If there is only one side cut then you have to push the  
> pin out by the clean side being careful to put your tool right in  
> the middle and realy straight so you don't scratch the bushing.  
> It's very important not to go all the way through with the tool  
> because you will push the bushing inwards tightening it the same  
> way that the tool for tightening key bushings works. This depends  
> on the tool you use… If the pin has cuts on both sides or it has  
> been filed then whatever you do will damage the bushing…  So,  
> pushing the old pin out can make damage to the bushing that will  
> result in tightening temporarly the bushing. Notice that I said  
> temporarly. if you put the same size of pin after a few weeks it  
> will be loose as it was the other one, or even worse if you loosed  
> the bushing  with a reamer or file for fitting the new one… If you  
> are repinning there is no way you will put same size pins, it have  
> to be at least one size up.
> I won't talk right now about sizing up the new pin, but once you  
> got it right then you have to be very careful tu put it straight  
> and push it with a straight surface so you don't tight it when you  
> press at the end (there are some tools that have an indentation for  
> the pin and can work as the key bushing tightener tool).
> So my assessment is that there is no wore in the pins but some kind  
> of swallow of the bushing while in the process of repinning.
> To test if something like this is happening just take one of your  
> tight repinned piece and apply one drop on each side pf protek  
> center pin lubricant and wait a few minutes and balance it a few  
> times and you will notice that it is loose. If this happens you  
> need to put in a thicker pin.
>
> Rafael
> _________________________
>
> Rafael M. Huberman Muñiz
>
> ArtePiano
> Jazmines #309, Col. Reforma
> Oaxaca, Oax. CP 68050
> México
> +52(951)5152629
> 044(951)507-0960
>
>
>
>
>
>






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