Re: [Harp-L] Why are there no washers on a harp?

["Tim Moyer" <wmharps@xxxxxxxxxxxxxxxxxxxx>]

Daniel Bernard wrote:
> I've never seen a harmonica with washers on it!  Is there 
> something I don't know?  Am I going to ruin a harp by 
> drilling out the holes and putting nuts, bolts and washers 
> on it?

I'm assuming you're talking here about both the bolts that hold on 
the cover plates, and those that secure the reed plates.  I'm at a 
loss for how you might have risked breaking the comb, though.  
Certainly there are screwdrivers with larger handles for better grip 
so you can get plenty of torque, but still with a small enough head 
to fit the screws in question.  

You have to remember that the screws that hold most harmonica 
innards together (securing the reed plates to the comb) are "self-
tapping" meaning that they're screwed into a hole in the metal that 
has not already had threads tapped into it.  Most screwed-together 
harmonicas are built this way.  In fact, you can look at a set of 
replacement reed plates and see that there are no threads in the 
holes.  The process of installing the screws simultaneously cuts 
threads in the plate and secures the plates.  

It has been a beef of mine for some time that when this is done at 
the factory no attempt is made to assure that the screws are 
actually torqued to some specification.  In fact, this inhibited by 
the fact that cutting threads requires some amount of torque greater 
than what is required to secure the plates uniformly.  As a result, 
you get uneven torques, which results in incomplete seals on factory 
harmonicas.  I tell people all the time that one of the simplest 
improvements you can make on an out-of-the-box harmonica that's 
assembled with screws is to simply remove the screws and put them 
back in, taking care to tighten them evenly.  Once the threads are 
already cut, you're only applying the torque needed to get a good 
seal, not trying to displace the metal at the same time.  

In all honesty, I think washers are unnecessary, since on a screw 
this small, without a lot of stress on it, distributing the tension 
uniformly across the head is not as essential.  Certainly adding 
parts and complexity to the assembly process would increase the cost 
of manufacturing.  But I would still argue that either tapping the 
plates as a separate step, or removing and reinstalling the screws 
at the factory would result in a much more uniform seal on an out-of-
the-box harmonica.  Tapping the plates prior to assembly could mean 
that replacement plates sold separately would already be tapped, and 
MUCH easier to install.  

-tim