Machining Glossary

A quick reference to the terms that come up most in machining and CNC work.

Common terms

• Chip load — the thickness of material each tool tooth removes per revolution; a key speeds-and-feeds input.
• Climb milling — cutting with the spindle rotation in the feed direction; better finish, needs rigidity.
• Conventional milling — cutting against the feed direction; safer on machines with backlash.
• End mill — a rotary cutter that cuts on its sides and end, for slots, pockets, and profiles.
• Feed rate — how fast the tool advances through material, often in inches per minute (IPM).
• Flute — the cutting edge and chip-clearing groove on a tool; counts vary by material.
• HSM — high-speed machining; light, fast, constant-engagement cutting.
• SFM — surface feet per minute; the speed of the cutting edge across the material, which sets RPM.
• Stickout — how far a tool extends from its holder; less is more rigid.
• Tolerance — the allowable variation on a dimension.
• Tool deflection — bending of the tool under cutting force, causing taper and chatter.
• Chatter — self-reinforcing vibration that ruins finish and tools.
• Workholding — how the part is clamped (vise, fixture, clamps).
• Trochoidal milling — a circular toolpath that keeps tool engagement constant.

Frequently asked questions

What’s chip load? Material removed per tooth per revolution.

Difference between SFM and RPM? SFM is edge speed across the material; SFM and tool diameter set RPM.

What is stickout? How far the tool extends from the holder — minimize it for rigidity.