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 -----Original Message----- From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Ron Nossaman Sent: Wednesday, January 24, 2007 4:04 PM To: Pianotech List Subject: Re: redrilling plates for 90 deg hitchpins > Any experience redrilling plates for vertical hitchpins > particularly in the bass bridge section of the plate? Yes. > The existing holes are drilled at an angle, and I'm sure > a redrill will try to follow the old hole and make a mess > of things. It will try, but... > In a chat with Del, the word was to shear the pin off at the plate, > spot the new hole center at the back edge of the old hole, > and drill 1/2 diameter through the old pin and 1/2 diameter > behind the old pin. > > Any other opinions on how to pull this off? Just looking for as much > experience/opinions as possible on this before jumping. In the bass, where I don't have room to move them, I try to pull them and use the old hole. A slide hammer with Vise-Grip often, but sometimes doesn't pull them. When it doesn't, I make a paper pattern of the hitch layout, and drill from the back side until I hit the existing hole and can punch them out with a hammer from the back. The rest of the plate is drilled through, and where I'm using the original pin locations, I punch them all out from the back. If I can get even one pin pulled, I have a hole I can drill through from the front to index the pattern underneath. > This is a small chickering quartergrand redesign, so there is > not much room behind the old pins to just move the pin > way back (or even forward on a few pins). I did one of these last year. The angled holes are a pain, but it's not as bad as it seems. Well, maybe it is, but it's doable. The biggest problem is that the bit migrates into the front of the hole, leaving a gap at the back. Structurally, that's not a problem because the support needs to be in the top half front of the hole, and the bottom half rear, but it sucks esthetically. I tried a lot of different things that didn't work as well as I'd have liked, and am currently doing it this way. After the old pin is out, I drill straight down the hole with a step drill (harvested from the local salvage yard). The tip is 0.1275", and the finish size is 0.185". The ground sides of the step don't migrate in the hole as much as sharpened flutes will, so the final size erases the evidence and leaves a clean looking hole (usually), at least on top. The flute lengths are short, and the step lets me drill that small pilot with the stiffness of a larger drill behind it so it doesn't try to follow the slant and break. The stainless steel roll pins I'm using are 0.196" diameter and 1" long, so the hole produced is still too small. I make another pass with a #10 bit to ream to final (0.1935") size. That couple of thousandth interference seems to be plenty to hold the pins tight. If you want tighter, go to a 0.004" interference, or whatever the supply source of your pins recommends. It doesn't take much, and what is effectively three drill passes in two actual passes tends to minimize sizing deviations more than anything else I've tried. I slightly chamfer the hole edges after drilling, with a low angle countersink (a rotary file, actually), and before finishing the plate. I touch a higher angle countersink to the holes again before the plate finish is hard, so I won't be whacking out chips later when I drive in the pins. A small, light hammer is ideal for this. That's my story and I'm sticking to it. Ron N
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