>> S&S Hamburg drills twice. >> Kaj. > > Do you mean to say they drill right through with a small drill and then > right through again with the final drill? That would be rather unusual > and I don't see the point of it. This is the first time I've heard of a manufacturer doing this, but I've been doing it for over 20 years. >If so, what size of drill do they use > for the first boring? I first make the marks with a sharp punch, then > use a centre drill and finally drill (right through or not, depending on > the piano) with a special (German) wrestplank drill which has a more > acute point than the jobber's drill and a faster spiral. I use 1/4" for the first pass, and 6.8mm for the second for 2/0 pins. >If drilling a > pilot hole right through would make the result more precise, I'd do it, > but I don't see that it would. It depends on your choice of pinblock, and how often you want to change drill bits. The softer Steinway style blocks, I'd tend to agree, won't see much if any benefit from double drilling to somewhere around 0.75mm under pin size. The denser blocks, like Delignit, most definitely show better hole uniformity with double drilling - unless you single drill with a new, or otherwise very sharp and accurate bit. I use a hybrid block I put together with a 9mm cap on the cheap maple laminate block. I transfer punch the drilling location, and hog the 1/4" bit through the block for the first pass, paying little attention to feed speed or bit temperature. The steam coming off the tailings is of no concern. The second pass is with a 6.8mm bit that I have used for many years on many blocks without replacement or sharpening. The result is a hole size uniformity and pin fit that I've never been able to come close to in one pass with any bit or method. A few others on the list have tried double drilling, on my hybrid block, or Delignit, and have reported similar results. They also report no obvious benefit to two passes in softer blocks. Ron N
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