Wednesday, June 20, 2012

Keeping Pads in Place

So you have a flute with French (open hole) key cups...   Have you ever wondered how the pads stay in the cups?  It's quite different since there is no center in which you can insert a screw.  With the closed-hole cups, there is a screw in the center of the pad that sits on top of a washer and the pad.  The screw is then tightened and secures everything in place in the cup.  But, with an open hole cup, there is a part known as the "French bushing" that keeps everything together.  French bushings can be either metal or synthetic, and both work in the same fashion.  Many people claim that the material has an effect on tone, but that is very subjective.  You'd have to try both and see if you hear a difference.

Just what exactly is the bushing, and how does it work?  Well, it's simply a small ring that is flattened at the top.  You slide it over the "chimney" of the key cup (and on top of the pad) and press it into place.  It keeps the pad secure by the force of friction.  Similar to the "chimney" in the open hole cup, a closed hole cup has a central "spud."  To hold a closed hole pad in place, the screw is fastened into this "spud" (with pad and washer in between).  With both types of keys, shims are used at the very bottom of the cup to seat the pads correctly.  Regardless of whether the key is open or closed, the shims are the same.  So if you've ever wondered just how a pad can stay in a key without a center, now you know!
Metal French bushings, pad washers, pad screws
Open hole key has a "chimney" in the center.  Closed hole key has a "spud."
Key shims to seat pads.  Shims are the same for both types of cups.
Just about to place metal French bushing in key cup.  Closed hole key pad in place with screw and washer.
Bushing in place! 

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