What is tensile strength?

This is a commonly used term when talking about the strength of materials. It is the load, usually stated in PSI necessary to break a piece of material by pulling it apart.

What is stress?

Stress is the load or pressure applied to something. Stresses relevant to machining are those applied to cutting tools, fixtures and parts while they are being machined.

What is strain?

Strain is material movement. For example, when a boring bar or end mill flexes under pressure or stress, it is said to be strained.

What does yield point refer to?

If you clamp a piece of bar stock in a bench vise and start pulling on the end of it, in the beginning you'll notice that the more you bend the bar the more force it will take to continue the bending. When you reach an angle where it no longer takes extra force but just steady force to keep the bend going that means the material is yielding.

Yield points can be shown graphically as the point of departure from a straight line on a stress/strain graph.

I'd like to see more information in Machinery's Handbook about "galling".

The word isn't even listed in the index. Based on my experience it is an important issue in regards to keeping tools and machinery running. I would like to know what materials, hardnesses and coatings work best and which ones work...