[pianotech] redrilling plates for 90 deg hitchpins

[Ron Nossaman]

On 7/11/2012 5:41 PM, Gene Nelson wrote:
> Resurrecting this post and this is why I did not delete any of it - but I
> would like to know - if one chooses to drill as Dell suggests below, not
> removing the existing hitch pins, where the bit would bisect plate and hitch
> pin when starting to drill, what sort of bit should be used - would a
> standard jobber work ok? Is this a multiple pass job? My guess would be that
> the bit would migrate toward the iron, away from the steel pin and tend to
> elongate the hole at the surface??
> Gene

The density of the steel and iron are similar enough that it tracks 
quite nicely. The smaller the initial hole, down to about half the final 
diameter, the easier it is to drill the hole and the easier it is to 
break the drill. Find a compromise that suits you and stock extra bits 
anyway. Any decent quality high speed split point jobbers bit works 
nicely. I use a step drill for the initial hole, because I found some 
about the right size at my local surplus yard years back for cheap and 
still haven't used them up, so I'm drilling the smaller size pilot hole, 
and a nearly finished size hole in one pass. This has proved to be a 
pretty ideal approach for me, as the step drill clears chips for both 
diameters easily and makes the biggest most accurately placed hole with 
the least work. I then ream to final size (third hole) with a second 
pass. As with drilling pinblocks, I find the final reaming pass of a 
slightly undersize hole makes a more controllably uniform fit. I use 5mm 
pins because I've found them to be adequately stiff, to present fewer 
spacing problems, and require the removal of a lot less iron than 
Baldwin's choice of 5.8mm.

My choices. Everyone slays their dragons by their own methods.

Ron N