Keyseating vs. Broaching: The Best Method for Internal Keyways
If you’re machining an internal keyway, your two main options are broaching and keyseating. Both work—but the right one depends on your part geometry, material, volume, and lead time.
In this quick guide, we break down the pros and cons of each so you can choose the right fit—and avoid unnecessary tooling costs or production delays.
Key Differences Between Broaching and Keyseating
| Feature | Broaching | Keyseating |
|---|---|---|
| Tooling Cost | High (custom broach required) | Low (standard cutter) |
| Setup Time | Long | Short |
| Blind Hole Compatible | ❌ | ✅ |
| Hardened Material Friendly | ❌ (limited) | ✅ |
| Best For | Large production runs | Prototypes, small runs, odd parts |
| Tolerance Range | ±0.002″–0.003″ typical | ±0.0015″ typical |
| Speed | Very fast (once tooled) | Moderate |
When to Use Broaching
✅ Use broaching when:
You’re producing hundreds or thousands of identical parts
You have a through-hole design
The material is mild steel or aluminum
You already have a broach tool built for the spec
But broaching breaks down when you’re dealing with:
Small batch or prototype work
Blind bores
Tight delivery schedules
Hardened materials (17-4, A2, Inconel)
Why Most Shops Switch to Keyseating
Keyseating is the flexible, low-cost alternative that works for 90% of internal keyway jobs we see.
It’s ideal when:
You don’t want to spend $2K+ on a broach tool
You’re cutting keyways in hardened or exotic materials
The part is a prototype, short-run, or rush job
The design includes a blind bore
Plus, keyseating delivers superior straightness, less taper, and better control over slot depth—especially useful for couplings, gears, shafts, and drive hubs.
Industries We Serve
We provide keyway machining services for:
Aerospace
High-precision keyseating for aerospace parts and components.
Automotive
Machines capable of creating custom keyways for automotive transmission and engine parts.
Construction
Heavy-duty keyseating equipment suitable for demanding environments.
Energy & Utility
Machines for keyway cutting in power generation and utility equipment.
Still Not Sure? Send Us the Drawing.
We’ll review your part and tell you in plain English whether keyseating or broaching is better.
If we can machine it faster and cheaper, we will. If broaching’s the better fit—we’ll tell you.