I just finished talking to Lawrence Pierce at Mapes Piano String Co. about how bass strings are made. He said the process hasn't changed much since the first wrapped strings were manufactured. He also said he knew of only one company in the world (Schimmel in Germany) that uses/used hex core wire in new pianos. (I've written to Schimmel to find out if that is true.) All the rest use round wire for the core. So what holds the wrapping in place?
The wrapping is held securely in place because the last 1-1/4" to 1-3/4" (before the wrap ends) of the core is swaged (or flattened) before the wrap is applied. The swaged portion, having two distinct, comparatively sharp edges, dents the softer copper wire as it is wrapped onto the core, holding the wrap firmly in place. (If the above explanation is hard to visualize, take a look at the picture below of an unwrapped string.)
The swaged portion is not created using any fancy machinery. According to Mr. Pierce, a simple two-piece die and a hammer are used to squash the steel core. And since that part of the string making procedure is done by hand, no two bass strings (from Mapes) are ever 100% identical, except by chance. Their similarities and/or differences lie in the hand of the person swinging the hammer. :-)
So swaging the core is part of the art of making bass strings for pianos.
Regarding Jon Page's comments about Mapes strings, I don't see how the space between the loop and the beginning of the winding could be any different than the original string. Here again, according to Mr. Pierce, the distance from the loop to the beginning of the winding is measured, the core diameter is measured and the overall diameter and winding length of the string is measure. Then, using a formula (he didn't tell me) which (evidently) accounts for normal stretching, the core is swaged and the new wrapping is applied.
Regarding making a knot in a broken bass string, I'd like to hear more about Jon's technique. I've been able to make the knot before, but man it was tough. It looks so simple in John Travis's 'Let's Tune Up' that I think I must be missing some little tricky part of the process that makes it a 1-2-3 deal like Jon says it is.
Fri, 14 Jan 2000 08:42:48 -0500
[ high resolution image: bassStr2.jpg (58kb)