Friday, April 26, 2013

Fitting Keys - Part I

One of the tasks that our flute finishers have is that of fitting keys.  The mechanisms involve several parts that must fit together in order to function properly, so the keys need to be "fitted" first.  Fitting keys takes several steps, but we had a chance to catch up with flute finisher Lindsey McChord to talk about some of the very early steps in the process.

Lindsey begins by taping the keys so that they do not get scratched in the finishing process.  Then, Lindsey begins the key fitting process by checking the mechanism tubing on each key.  When the key mechanism is assembled, a steel rod (or "steel" as it is commonly called in the shop) runs through the inside of the key mechanism tubing.  In order for the keys to move smoothly on the steel, the inside of the tube must be a perfect cylinder.  Sometimes, the inside of the tube still needs a bit of tweaking when it arrives at the finisher's bench.  So, a small gauge that looks like a double-ended screw driver is used to check the inside of the mechanism tubing.  This gauge is referred to by finishers as the "go/no go gauge."  This gauge has a green end and a red end.  If the green end of the gauge fits smoothly and evenly into the mechanism tubing, the key is a "go" and does not need any further work.  If the green end does not go in smoothly, there is a problem at hand.  If the red "no go" end goes into the tubing, the key is overly reamed and must be returned to the stringing department (which supplies key mechanism components to the finishers).

The "go/no go gauge" is used in a few different ways to help determine what might need to be adjusted on a key's mechanism tube.  If the green end goes in smoothly at both ends of the tube, the key is "good to go."  If it does not go in at all, or if it is extremely difficult for it to go in, the mechanism tubing needs to be reamed.  When reaming the tube, material is removed from the inside so that it is smooth and cylindrical, with an even diameter throughout.  If the gauge goes in but feels a little loose or a little tight in one area of the tube, the tube is "spun" by the finisher -- which is essentially a step used to even out the inside of the tube.

To spin and ream tubes, the finisher uses the bench motor with a steel that has a flat end and a pointed end.  To ream a tube, the steel is placed in the bench motor with the pointed end facing outward.  The motor is turned on, and the reaming tool spins very quickly.  The finisher runs this reaming tool through the tube to remove excess material inside.  A very straight motion is used in the reaming process.  In the "spinning" process, which evens out the inside of a tube, the same steel is placed in the bench motor -- but the flat end of the steel is facing outward.  The key is place on the steel, and the motor is turned on.  The finisher is then able to grab the end of the steel and "spin" it in a circular motion to even out the inside of the tube.  The finisher may use a tissue or paper towel to grab the end of the steel so that s/he does not hurt her/his hands.

There are several additional steps to fitting keys, but checking the mechanism tubing to make sure the steels run through smoothly is one of the first steps to key fitting.  Stay tuned for future posts as we explore more on the topic of key fitting.

Taping keys so they do not get scratched.
The "go/no go gauge" -- red for no go, green for go!
The red "no go" end is not going in, so this is good!
Testing the green "go" end.  It should fit in smoothly throughout the tube.
Pointed end of the steel used for reaming.
Steel in the motor, getting ready to ream.
Reaming the key mechanism tubing with a very straight motion.
Changing the steel for spinning.  A longer portion is used, and the flat end faces outward.
The steel is "spun" in a circular motion during the key "spinning" process.
Key placed on the steel, getting ready to spin the mechanism tube.

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