The grooves for tuning slides in wood pipes are always best cut before
the pipe front and back are glued up.  After the sides are glued to the
pipe block and a scrap block at the top, the inside depth is accurately
machined and then the grooves are cut either with a square tooth blade
on a table saw, or a router bit with a guide to control how far it can
cut into each side.  Immediately after gluing, the groove is cleaned
out with a modified spring hook ground to a sharp edge suitable for
scraping out the groove.

On very short treble pipes, the tuning slot must be cut in the back
so the slide does not interfere with the mouth.  Occasionally the slide
is on the side of the pipe.  For this situation, the front and back
receive the groove with a very thin saw blade.  They are accurately
located before gluing by using a piece of slide material and pegged
into place.

If it is necessary to cut the groove after gluing, a thin saw blade
such as a hacksaw blade can be ground to suit the application.  The
spring hook can also be used, but it is easy to let the groove wander
away from the corner of the pipe which causes tuning problems.

To fit slides accurately, we make up quantities of slides in 1/2 mm
increments and just select the best fit.  That way, only a little
de-burring and notching is needed.

The tuning slot is cut after the pipe is glued up and trimmed to
length.  Our preferred method is to use a mill.  The pipe is clamped
in a vise and the milling table centers the cutter on the pipe.

John M. Nolte - Nolte Organ Building & Supply, Inc.
Milwaukee, WI