Reference & Selection Guide
Every indexable insert is a trade-off between edge strength and accessibility. Getting the point angle right is often the fastest way to cut cycle time, stop chipped edges, and hit the surface finish you need — before you even touch feeds and speeds.
Insert shape is defined by its point angle — the included angle at each cutting corner. A larger angle packs more carbide behind the edge, so it resists chipping and shock. A smaller, sharper angle leaves less material behind the edge, but lets the insert reach into corners, profile contours, and cut in more feed directions. Every shape on the market sits somewhere on this spectrum, from the round insert (no point angle at all, maximum strength) down to the 35° diamond (sharp, maximum access).
The same spectrum runs in reverse for machine demands. Stronger, blunter shapes need more spindle power and torque to push through a heavy chip, but they run smoother with less vibration relative to the depth of cut they can take. Sharper shapes cut with less force and need less power, but concentrate heat and stress at a smaller tip, so they're more prone to vibration and edge wear under a heavy load.
A quick reference for what each shape is actually good at.
The strongest and most durable shape, with no weak corner to protect. Best for heavy roughing, hard or abrasive materials, interrupted cuts, and high feed rates.
Four (or eight, if double-sided) strong 90° corners. Best for roughing, squaring shoulders, hard materials, and interrupted cuts.
The most common turning insert on the market — a genuine balance of strength and versatility. Handles roughing through finishing, turning and facing.
Three corners give more usable cutting edges per insert than the C shape, for better tool economy at a similar strength.
Three (or six, double-sided) edges and a comfortable middle ground. Good for semi-finishing to finishing, low machine power, and low vibration.
A favorite for contour and copy turning. Best for profiling, finishing, and semi-finishing where you need to follow a shape.
The most pointed shape, for reaching into corners nothing else can. Best for fine profiling and finishing — light cuts only.
How each shape stacks up across the factors that actually drive a shape decision. Scroll sideways on smaller screens.
| Shape | Roughing | Semi-finish | Finishing | Turn & face | Profiling | Versatility | Low power | Low vibration | Hard material | Interrupted cuts | Small lead angle | Large lead angle |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Round | ||||||||||||
| 90° Square | ||||||||||||
| 80° Diamond (C) | ||||||||||||
| 80° Trigon (W) | ||||||||||||
| 60° Triangle (T) | ||||||||||||
| 55° Diamond (D) | ||||||||||||
| 35° Diamond (V) |
Not sure where to start? Match your job to a shape.
Ready to shop inserts? Browse our full turning insert catalog, or decode an existing part number with the Insert Designation Chart.
Ready to cut
Once the geometry is settled, the grade and the holder decide how long it lasts. Browse the turning line built for tight tolerances under aggressive feeds.
Not sure which grade matches your material? Use the Grade Look-Up.