Overhead Router Jig for Planing Piano Keys

More photos at FlickrPreparing an old set of piano keys for new key tops is a critical operation. I designed and built this router jig to perform the operation of keytop planing with accuracy and speed. To preserve the geometry of the piano action, 1 mm will be planed from the key to account for the difference in thickness between the old ivory key top and the new plastic key top. This also produces a good flat glue surface for the new key top and a nice square notch at the rear for a professional appearance. The old ivories needed to be replaced because of extensive cracking, chipping, and missing pieces.

More photos at Flickr
The photo to the right shows the key after exiting the jig. Note that the clamping mechanism is a simple, quick lever which holds adequately and keeps the process moving. The loose plate between the key and lever is coated on the lever side with some beads of hot glue, to provide gripping surface that would not be present in the hard maple. The router bit is a 1-1/2 diameter flat cutting bit. Since the key is less than 1 inch across, this diameter provides a cutting surface for both left side and right side of the key. Order of operation is:

1) With jig against right shoulder insert into about 1/4 inch. move to the left to plane the front edge of of the key (and the existing key front).
2) Slide the sled in to plane the left side of the key.
3) Move the sled to the right, forming the nice edge at the back of the key.
4) Pull the sled out to plane the right side of the key.

This order of operation will provide for proper rotation orientation of the cutterhead and produce a splinter free surface.

The objectives of accuracy and speed are met. This set of 52 keys was planed in 45 minutes.

More photos at Flickr

2 thoughts on “Overhead Router Jig for Planing Piano Keys”

  1. Additional details … from discussion on PianoWorld.com Forum:

    The Spurlock article which was my beginning point is the March 1991 issue of the PTG Journal.

    The key set I worked with for this first go was really in good shape. There were no warped keys. I would say that the left side of the key (in the photos — right side in the piano) is the reference edge, and that the jig makes a cut perpendicular to that edge. The loose plate adjacent to the lever has less bearing surface than the fixed block. To set the clamp, I provided a light down pressure for reference to the sled’s top, then clamped it tight against the block.

    For this key set, the tail was relieved relative to the ivoried key length, so the back of the key was actually not in contact with the sled, but a millimeter or two above the sled. But I can see that an elevated contact points at the front and rear of the ivoried key length would eliminate problems for another key set. For this one, I judge my success by the uniformity of the rear profile of the cut.

    The width between sides of the jig is 300 mm. The sled is 262 mm wide. Other dimensions are determined by the key. I’m giving you my working sketch here: http://www.flickr.com/photos/duanemcguire/4150416852/sizes/l/ Consider it to be my starting point. I know it is not an “as built” diagram, since I went direct from concept to finished product. In particular the sled and base are longer than indicated in the sketch. They were built to a more “comfortable” length.

    The base and sled are made of melamine faced particle board for slipperiness. The inserted end of the sled has a pair of sliding closet door rollers on it for smooth use and to assure that particles on the floor of the jig do not interfere with the reference cut.

    The plated hardware on the front of the slide are rollers sold as sliding door glides at the local Lowes hardware. The purpose is to make the cross cut smooth. Also by using the roller point above the floor of the jig, any chips/debris that the dust collection misses will not interfere with a true reference to complete the straight cut at the back of the key.

    I found that the simple quick clamp was trouble free and solid for this key set. Another clamp at the rear of the ivoried section would provide additional security. I was going for for the min-max of hardware/accuracy. For this key set it was perfect. I expect it will evolve some with different key sets in the future.

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