Cutter sources: Drilling Performance

Every machine shop has to decide whether to make cutters or buy them. A similar decision exists for regrinding cutting tools in-house or paying a company to perform the service.

Another consideration is tool coatings: what coatings to use, when to apply coated tools and whether a tool is recoated after resharpening.

A small percentage of toolmakers grind and produce most of their own cutting tools from solid-carbide blanks. In addition to producing their own standard cutters, these toolmakers must design specials for specific jobs.

In operation, tool life is targeted for a specific number of minutes, and then all cutters are resharpened. Shops that grind their own new cutters also resharpen them because the grinding equipment can perform both tasks. However, some shops report lower tool life from resharpened cutters.

To maintain the production of high-quality parts, new cutters are often used for finishing, and resharpened cutters are relegated to roughing. Two shops that grind their own claim they are able to produce a more accurate cutter than one that’s purchased.

When milling titanium alloys at less than 70 sfm, I do not recommend applying coated tools. This slow milling speed applies mostly to roughing with cobalt tools. If it is important to coat a new cutter, then it is equally important to use the same coating after resharpening the tool. Recoating presents a logistical problem because most shops are not capable of coating tools. The usual practice is to overnight cutters to a coating company.