Captive Back Tool

Tapered Deep Hollowing System

The Tapered Deep Hollowing System was designed by Mark St.Leger and is manufactured by Mike Hunter.  The components to this new system are two boring bar choices (listed below) and a three-tool cutter package.

Boring Bars

1. a 16” long, 1” diameter boring bar with an adapter size of ¾” at one end and a 3/8” tool receptacle with 4 grub screws at the other end.
2. a 12” long, ¾” diameter boring bar with a 3/8” tool receptacle again with 4 grub screws.

The reasoning behind having four grub screws is simple: if two get messed up, there are two more to take their place. It is actually a good practice to tighten all four grub screws. There is a lot of torque at the tool tip at 17” of depth (someone aggressive might just spin the tool with only two tightened).