[pianotech] Hammer Boring Jig

[William Truitt]

HI Jon:

I started out with the Brooks jig made out of multilaminate wood many years
ago.  I noticed that when I bored, there was some flex downward at the end
that was not supported in the drill press clamp.  Some years ago, I bought
the Renner hammer boring jig, which I have found to be more consistent, and
does not flex at all.  I don't know what else is out there, but I would not
consider anything that did not have support at both ends.

Some other caveats, which you probably already know:

Keep your drill bits sharp, and start the first contact with the molding
with a very slow feed so as to avoid skating when the hammers are at an
angle other than 90 degrees.  Also, use short hammer boring bits, such as
you can get from Pianotech, and keep the exposed bit as short as possible,
all to avoid flexing of the drill bit.

I have a dedicated hammer boring drill press - just a cheapo little $99
dollar one.  That way I do not have to go to the hassle of setting it up
every time.  It takes a while to set things up so that the holes are dead
center, so this way I do not have to find the center every time.  It's worth
the investment.

Some of the softer molding woods such as walnut or mahogany can create
centering problems - the drill bit wants to travel to the soft grain, and
the drill bit will sometimes wander from the hard grain where it is supposed
to enter.  This is where the short, sharp drill bits are most helpful, or
get a harder molding wood such as maple.

The quality of the cutting of the hammer felt has everything to do with
getting a consistent result, even if you are controlling the other variables
as above.  We've all seen hammers that vary in width (sometimes as much as
.050 or .060 inches).  Also if the cutting is not a straight line vertically
or not at 90 degrees fore and aft, this can create problems also.  These
conditions can result in hammers that are not consistently centered, despite
your best efforts.

What other things are you doing in terms of hammer preparation?

Will Truitt


-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Jon Page
Sent: Saturday, May 01, 2010 1:54 PM
To: pianotech list
Subject: [pianotech] Hammer Boring Jig

While my present jig is accurate, I want more precision.

Would the Renner USA jig be the way to go or are there others to consider?
-- 

Regards,

Jon Page