[pianotech] pinblock drilling clamp

[Mike Spalding]

Ron,

OK, that fits with what I've experienced.  My second pass drill is a 
conventional F jobbers bit, but I want to use a brad point for first 
pass; it's easier to align with the transfer punch marks.  I'll look for 
a 6mm brad point.  I believe you've commented in the past that your 
second pass drill bit has been in use for many blocks, dulling does not 
seem to be an issue.  Did you find that initial sharpness of the new bit 
was detrimental - is there any advantage to dulling the tip of a new bit?

thanks

Ron Nossaman wrote:
> Mike Spalding wrote:
>> Wim,
>>
>> The problem you have solved is not the problem I was having.  During 
>> the second pass, when the .257 drill enters the .219 hole, it can 
>> grab and lift the pinblock at any point during the feed, not just at 
>> the end when it penetrates the bottom of the block.  By clamping the 
>> block securely during the entire stroke, not only is this 
>> grab-and-lift prevented, but any random shifting of the pinblock that 
>> might make the hole slightly larger is also prevented.
>
> Mike,
> A couple of things; The diameter difference I use between first and 
> second pass is 0.018". Yours is 0.038". I'd recommend something more 
> along the lines of a B or C, or 6mm for the first pass. The more wood 
> you remove on the second pass, the less effective the two pass 
> approach is, and the more likely the second pass will grab and burrow. 
> The other point is the type of bit used. A high spiral bit on the 
> second pass is the kiss of death, and pretty much guaranteed to grab. 
> Regular old non exotic jobbers bits work nicely. You don't even need 
> to cool the drill.
> Ron N
>