Overview

The purpose of this chapter is to present parameters for milling some difficult features in titanium alloys. The chapter begins with a review of efficient milling feeds, speeds, coolants, and avoidance of cutter burns, but primary focus is on milling thin webs and thin flanges in titanium alloys without the expense of back-up tooling, and on producing rough finishes in response to an unusual request. I have spent the past fourteen years developing processes for fabrication of defense and space parts from titanium alloy plates and castings. These processes were developed during the period 1991 1997, while resolving various milling problems on titanium alloy parts.

The order of reporting is:

1. Fundamental milling parameters for titanium alloys

2. Milling thin webs in titanium alloys

3. Milling thin flanges in titanium alloys

4. Producing a rough surface

Fundamental Milling Parameters for Titanium Alloys

As a synopsis, when milling titanium alloys, sfm (surface feet per minute) are 60 sfm (18.3 m/min) maximum for cobalt (M42) cutters and 120 sfm (36.6 m/min) maximum for solid carbide (micro-grain or sub-micro-grain carbide) and carbide insert cutters. Chip loads are usually 0.005 in. (0.127 mm) and a maximum of 0.008 in. (0.203 mm) per tooth for both types of cutters. This study on difficult sections was written prior to the breakthroughs in milling reported in chapters 6 and 7.