HHIP Indexable Tool Set with 3" Boring Head, R8 Shank and 8 Boring Bars. Boring head features a 1-1/2"-18 threaded back so you can change shanks as needed. A micrometer lead screw provides 0. 001" direct reading accuracy and makes adjusting easy. Boring head offset is 1". Minimum boring diameter is 0. 394". Maximum boring diameter is 7. 874". Maximum boring depth is 3. 150". The cross hole is 3/4". R8 shank has a drawbar end thread of 7/16"-20. The included indexable boring bars come with TCMT 21. 5 C6 carbide inserts for steel and alloy. The set also comes with torx & l-shape hex wrenches and a fitted carrying case. 1 DIV = 0. 001 which means when turning the dial by 1 division/graduation, on the 0-100 dial, the boring head's travel is 0. 0005" in radius movement, 0. 001" in diameter movement.