Page:Practical Treatise on Milling and Milling Machines.djvu/95

Rh CHAPTER VI Cutters

The development of the manufacture of milling cutters, and a better understanding of their care and use, have resulted in a rapid growth in the number and variety of milling operations, and a corre- sponding increase in the sizes and varieties of cutters. It is evident, therefore, that the selection, care and use of milling cutters are points of utmost importance in attaining success in the process of milling. The failure to obtain commercial results may often be attributed to the fact that the wrong cutter has been used on a certain job, or even if the right cutter has been chosen, the work has not been done under the most favorable conditions.

Either the operator or the person in charge of the job should be proficient in the selection and care of cutters, and capable of determin- ing the correct speeds and feeds at which to operate them. No theoretical knowledge of the design and manufacture of cutters is necessary to aid in this work, although a general understanding of these points is of material help. While we are able to give in the following pages such information as applies in common to the running of milling cutters, the most valuable experience will come only through actual work at the milling machine.

Carbon and High Speed Steel. Milling cutters are made from either of two varieties of steel, known as Carbon Steel and High Speed Steel. Those made from High Speed Steel can be subjected to more severe service than those made from Carbon Steel, and they are especially desirable where large amounts of metal must be removed rapidly, as in roughing out pieces of work. Cutter manufacturers can usually furnish all styles and sizes in either steel. No fixed rules can be given for their choice. The requirements of each job and experience in the use of cutters must determine which steel is more economical and will give the most satisfactory results.

Plain Milling Cutter. This is a common type of cutter found in every shop, and may be described as a cylinder having teeth on the periphery only and producing a flat surface parallel to its axis. It is manufactured in a large variety of diameters and widths to meet