Speeds and feeds are the most important considerations to achieve the best results from cutting tools. Improper speeds and feeds often cause low production, poor quality, and damage to the tool. Speeds that are too high or feeds that are too light can lead to rapid wear and dulling of the cutter, reducing tool life.
Speed is measured in peripheral feet per minute. It is often referred to as cutting speed or surface speed. Feed is usually measured and stated in inches per minute (IPM). It takes into consideration the number of cutting teeth (or flutes), the feed per tooth (or cutting edges), and the revolutions per minute.
Coolant can dramatically affect the performance of cutting tools, which can
impact the cost of your operation. Consider these guidelines for using coolant:
Cutting fluids perform two basic functions in drilling, milling, and threading:
1. to reduce heat generated in cut;
2. to lubricate the tool.
Water-based coolant helps to cool the chip when it is sheared from the workpiece material.
PVD TiN (Physical Vapor Deposition Titanium Nitride) coatings are the primary general-purpose coating for end mills, but TiCN (Titanium Carbo-Nitride) and TiAlN (Titanium Aluminium Nitride) are becoming popular in use. Common questions for milling applications include when to use these advanced coatings, and at what speeds to run them.
TiCN is a harder coating than TiN and has good abrasion resistance. It is very good in milling applications for steels, stainless steels, and non-ferrous materials. End mills coated with TiCN should be operated at speeds up to 50% higher than uncoated end mills.
Work hardening of materials is a condition that should be avoided while machining. It is caused when heat generated by the cutting tool transfers to the workpiece material and causes plastic deformation. The process is similar to a heat treatment of the workpiece but on a lower scale.
When a part work hardens during machining, its surface becomes a shiny glaze and appears slippery. The machined part can even take on the same hardness as the cutting tool.