Tuning pin drilling? followup

[jimialeggio5 at comcast.net]

>A .272" bit seems large for a Delignit block. A .257" (F) bit is what 
I> usually use
>in a drill press, I found that even a .261 (G) bit was too loose.

>Generally .010 smaller than the pin was for Falconwood blocks.
-- 

>Regards,

>Jon Page


The discrepancy between what diameter bit is used by different operators and 
different drilling rigs point to the inherent inaccuracies of the the drill press and the 
way tooling is used in a drill press.

To start with, the quill has slop, and the further the quill plunges the more 
pronounced that slop becomes.  Now add to that inherent slop that the 4" or 6" 
drill bit is: 1- often not dead straight, 2-often inserted into a non-precision 
chuck, thus further spinning out of true, 3-the drill bit tends to deform its 
axis as it spins, 4-the bit often skates a bit when starting the hole, thus 
entering the wood outside the drill press'  axis, even further deforming the 
already deflected axis. Then in addition to all this these above variables the 
speed of the plunge further affects the behavior of the deflections.  

In my opinion, a dilled hole is a complex construction.

For these reasons a drill press is not the tool of choice in a machine room 
where repeatable precision is required...a bridgeport is often preferred for machine precision.

We are not in a machine room. The drill press' inaccuracies are present in any 
drill press, top of the line or yard sale beauty queen. As I see it, the object of the 
game is to understand the inherent nature of the machine, understand our machines' 
particular quirks, and adapt the process to accommodate those quirks. 

The appropriate size of the bit is merely an indication of how much deflection 
is being allowed by a particular drilling rig. If two different rigs are are drilling the 
same material and getting the same finished torques using a .272  and a .257 bit respectively with the 
same plunge timing, the larger bit is spinning truer to axis throughout the cut. 

That difference really doesn't necessarily mean anything.  My point here is that 
we need to understand the inherent inaccuracies of the machine, and the inaccuracies of our 
particular machine/set-up in order to trouble-shoot our own respective procedures effectively.

Secondly my point is, if one chooses, for whatever reason, to use  an 
unforgiving quasi-wood product like Delignit, the above inherent and specific inaccuracies will become 
accentuated.  That can be ok...as long as one understands what parameters of the operation need to be to 
controlled. 


Jim I