TECH TIP – Tool Bit Selection

Tool bit image

Obtaining the best results starts with selecting or determining which tool bit to use with the material being cut. Tri Tool has three basic cutting edge geometry’s which function well on most of the common tubing materials.
In addition to variations in the edge geometry, tool bits are made available from M-42 tool steel, variations in height and combinations of all three as shown in the accompanying table. Selections of the tool bits should be based on tubing material, how critical it is to have a neat burr-free end and tubing size.

General guide lines for selection of the tool bits are:

  • Use a STANDARD ENTRANCE ANGLE tool bit for carbon steel. These bits may also function well on some stainless steel applications where a near burr-free end is not critical and will provide longer bit life.
  • Use a HIGH ENTRANCE ANGLE tool bit for most stainless steels. Generally the most suitable edge geometry for 90% of all stainless steel tubing.
  • Use an EXTRA HOOK ANGLE tool bit for stainless steels which are very soft. These stainless steels include materials like 316L which have been bright hydrogen annealed, vacuum annealed or annealed and electropolished. As drawn tubing normally runs above 80 Rb versus as low as 76 Rb for annealed and electropolished low carbon stainless steels. Also, the electropolished stainless steel has a micro-thin surface which is high in chromium and nickel making it very soft, but tough and difficult to cut without creating a burr.
  • Use a .969″ (24.5 mm) TALL TOOL bit for 3/16″ (4.76 mm) or less tubing. Also the tall tool bit may provide some advantages for thicknesses less than .020″ (.5 mm). The tall tool bit will cut very close to the collet face which minimizes flexing of the tubing from the cutting pressure. Use of the tall tool bits requires more time to adjust the tube position for cutting and there is some risk of crashing the tool bit into the collet on larger OD tubing.
  • Use M-42 TOOL STEEL bits for exotic alloys where the high heat resistance is required to avoid burring the cutting edge. The M-42 can also improve the life expectancy of the bit under some conditions on stainless steel. However, because M-42 tool is more brittle then M-2 there is a much greater risk of damaging the tool bit when installing the tube in the tool and loss of tool bits from damaged edges may not offset the improved cutting life.
  • Some of the exotic alloys may require an EXTRA HOOK ANGLE bit as well as M-42 tool steel for heat resistance.
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