Internal Tube Cutter - PR68 Series It is ideal for cutting thick walled boiler tubes. Features of Internal Tube Cutter - PR68 Series PR-68 tube cutters are ideal for tube cutting thick walled boiler tube of 2” O.D. and higher. The Internal Tube Cutters PR-68 is driven via the square in a clockwise direction using either an electric, pneumatic or hydraulic driving machine. PR-68 type tube cutters are available in standard reach of 4” (101.6mm). Additional reaches in increments of 4” are available up to 16” (406.4mm).