Up against a deadline to ship engines, we elected to machine the 20 chrome water necks to fit, rather than return them and order more. To securely hold the water necks in our lathe, we needed a custom-sized expanding arbor. I made the arbor from a 4″ length of aluminum round bar, and a 3/8-16 x 1″ flat-head hex-socket screw. In the lathe, I face the round bar, then drill a 2″deep hole, and tap about 1.25″ deep, 3/8-16. Now countersink the round bar just enough to allow the flat head screw to seat fully, but not deeper. Next, remove the screw and use a band saw (or hacksaw) to slit the round bar lengthwise ~2″, at 90°, making 4 slots. Back in the lathe, install the screw until it just seats, then turn the OD of the round bar to its final size for a snug fit that allows the workpiece to be pushed onto the arbor. Now just tighten the screw to expand the arbor. It took 10 minutes to make, and we started machining. I’ve found that using a flat-head screw to expand the arbor is more accurate and repeatable, and it wears less after repeated use.
Tom Nichols
Automotive Machine & Supply, Inc
Cleburne, TX