CNC Machining Cheat Sheet

Keep this reference beside the machine or programming desk. It collects the relationships used most often in day-to-day CNC work.

Core equations

Task	Formula
RPM from SFM	RPM ≈ 3.82 × SFM ÷ D
Feed	Feed = RPM × teeth × chip load
Chip load	Chip load = Feed ÷ (RPM × teeth)
Milling MRR	MRR = Feed × radial engagement × axial depth

Before cycle start

1. Correct program and revision.
2. Correct tool and holder.
3. Tool lengths/radius offsets checked.
4. Work offset verified.
5. Stock/workholding correct.
6. RPM/feed within machine/tool limits.
7. Safe rapids and Z checked.
8. Coolant/chip evacuation ready.

Fast troubleshooting

Problem	Start with
Chatter	Rigidity, overhang, engagement, controlled speed change
Poor finish	Runout, tool condition, feed, toolpath
Tool breakage	Engagement, chip load, tool seating, collision risk
High spindle load	MRR, engagement, tool geometry, machine limit

Speeds & Feeds · Chip Load · MRR · Machining Time

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