Cutting Tool Basics (End Mills, Inserts, Drills) — Types and How to Choose

How you choose cutting tools greatly affects efficiency, finish, and tool life. This article compiles the tool types commonly used in milling and turning and how to choose them.

End mills (for milling)

Type	Traits / uses
Square end mill	Flat bottom. Slots, flats, contours
Ball end mill	Rounded tip. Curved and 3D shapes
Radius end mill	Cornered with an R. Chip-resistant, high efficiency

Choosing flute count

Flutes	Traits	Suited materials
2-flute	Great chip evacuation, good for slotting	Aluminum, plastic
4-flute	Rigidity, good finish	Steel, stainless

Carbide vs HSS

	HSS	Carbide
Hardness	Medium	High
Toughness	High (chip-resistant)	Low (brittle)
Speed	Low–medium	Good at high speed
Use	General, interrupted cuts	High speed, high accuracy

Lathe inserts

A disposable edge — the "indexable insert" — mounts in a holder. Choose the shape (OD, facing, threading, grooving) and grade (P: steel, M: stainless, K: cast iron, N: aluminum...) to match the workpiece.

Drills

• HSS drill: general-purpose, tough
• Carbide drill: high speed, high accuracy
• For deep holes, mind chip evacuation (peck drilling, coolant)

Coatings

Coating	Traits
TiN	General, wear-resistant
TiCN	High hardness, wear-resistant
TiAlN	Great heat resistance, for high speed/hard materials
DLC	Prevents built-up edge on aluminum, non-ferrous

FAQ

Q. How many flutes for aluminum? A. 2-flute for good chip evacuation. A DLC coating also helps prevent built-up edge.

Q. Carbide or HSS? A. Carbide for high speed and accuracy; tough HSS for interrupted cuts or chipping concerns. Choose by cutting conditions.

Q. What are P, M, K on inserts? A. Workpiece classification codes. P = steel, M = stainless, K = cast iron, N = aluminum... a guide for grade selection.

Conclusion

Choose tools by "workpiece × operation × required finish." First grasp end mill shapes and flute counts, and the carbide-vs-HSS difference.

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