Yet another Boring class

Last time: Straight hole Taper hole Contour hole

Boring head Adjustable tool holder for boring bar. Has micrometer adjustment for bore size. Direct reading (a .010 change opens the hole .010 NOT .020)

Tool construction Body attaches to arbor or tool holder in machine Dial screw provides adjustment Bar holder retains tool Boring tool cuts metal

Boring Advantage One tool cuts infinitely many diameters Single point tool is less likely to chatter Hole is perfectly round Disadvantage Slow operation due to imbalance “Cut and try” adjustment

Reaming v. Boring

A ream must remove equal amounts of metal from both sides of a hole, a boring head doesn’t need to. Hole location can be corrected with a boring head... not a ream

Tips from the good people at Criterion Suggestions For Better Boring Head Performance Cutting edge of tool must be on center line. Tool sharpness for boring is more critical than for O.D. work. Keep tool overhang to a minimum. Use power feed whenever available. Make allowances for "spring" or deflection when taking a heavy cut. Additional material will be removed on finish cut even though an additional adjustment has not been made. When using carbide, avoid reversing or stopping the spindle in the middle of a cut. This can cause chipping or breakage. For best surface finish spindle should be turning while tool is being retracted from the bore. Avoid "bottoming-out" in a blind hole. A boring tool is not designed for end cutting.

Tip from your Fearless Leader Take a cut heavy enough to “pre load” the tool for cutting accuracy. A “heavy” cut can be more accurate in some circumstances because tool deflection has been minimized.

What if we turn the bar around?