High-speed aluminum, without the chatter
Aluminum isn't “easy” at production speed — thin walls chatter, floors distort, and witness marks mean hand finishing. Here's how RobbJack's geometry runs aluminum at max RPM and still leaves a finish you can ship.
What actually slows aluminum down
It's rarely the metal — it's vibration and distortion forcing you to be conservative. Fix those and aluminum runs as fast as your spindle allows.
Chatter
Vibration in deep pockets and thin walls that forces you to back off the feed.
Witness & swirl marks
Mismatch lines and swirl on walls and floors that mean hand finishing.
Thin-floor distortion
Oil-canning, residual stress, and heat that pull thin floors out of tolerance.
Deflection on reach
Long tools deflecting in deep pockets, costing accuracy and finish.
Mirror Edge™ — the anti-chatter edge
Mirror Edge is an edge preparation that damps the cut to eliminate chatter. Paired with polished flutes, it lets you run aluminum at maximum RPM in the cuts that normally vibrate — deep pockets, thin walls, and long reaches over 3:1 length-to-diameter — and it works for plunging corners in steel, stainless, and titanium too. The one rule: always run it with coolant.
Because the cut stays quiet, you don't have to back off — which is where the big cycle-time wins come from. RobbJack aluminum tooling has turned multi-hour jobs into minutes and cut cycle times by 500% or more versus conventional tooling.
Pick the right aluminum tool
Five families cover aluminum from heavy stub roughing to ultra-high-RPM finishing. Match the family to your reach, your machine, and the cut.
Heavy stub roughing; reduces horsepower for full slots
Mirror Edge workhorse up to ~3:1; targets machines under 25K RPM
Long reach (3–5×D LOC), thru-coolant & corner radii; finish deep walls in one pass
Deep pockets and thin walls over 3:1, with Feather Blend transition
Ultra-high-RPM / high-HP machines; thru-coolant, quantity-based
| Comparison | A1-201 | A1-303 | AL3 | FM | FMHV |
|---|---|---|---|---|---|
| Tool features | |||||
| Mirror Edge | · | ||||
| 3–5×D length of cut | · | · | · | · | |
| Short depth of cut | · | · | |||
| High-RPM machines | · | · | · | ||
| Necked options | · | · | · | ||
| Corner-radius options | · | · | |||
| Coolant-thru optional | · | · | · | ||
| Polished flutes | · | · | · | · | |
| 2 flute | · | · | |||
| 3 flute | · | ||||
| Chip breakers standard | · | · | · | · | |
| Balanced 3-flute | · | · | · | · | |
| Quantity-based pricing | · | · | · | · | |
| DLC available | |||||
| Multiple OAL available | · | · | · | ||
| Applications | |||||
| Under 25K RPM target | · | · | · | ||
| High-speed / high-HP machines | · | · | · | ||
| Thin wall | · | · | · | ||
| Roughing / finishing | · | ||||
| Trochoidal milling | · | · | · | ||
| Heavy stub roughing (high CLPT) | · | · | · | · | |
Starting recipes that work
A1-303 — general aluminum
- Polished flutes, run at max RPM
- Mirror Edge — use coolant
- Axial depth of cut: 2× diameter
- Radial step-over: 50%
- Chip load per tooth: diameter × .016"
AL3 — deep walls & pockets
- AL3-303: slot 1×D axial / profile 50% step-over, 2–3×D axial
- AL3-304: profile 30% width, 4×D axial
- AL3-305: profile 10% width, 5×D axial — 14,000 RPM, 236 IPM
- Engage enough cutting length to stabilize — don't just use the tip
- Long tools may need a spring pass or two for finish
Starting points — the Speeds & Feeds calculator tunes these to your exact tool, material, and machine.
Thin walls
The mistake to avoid is skim-passing a thin wall — light passes just make a tall, thin wall flex and push away. Instead, waterfall down and finish at every Z-depth: rough and finish each step to final size before going deeper, and never re-cut a wall at a depth you've already finished.
Leave at least .100″ on the wall for the finish pass (not a skim). Because you finish level by level, the wall is only ever as tall as your step-down — a 1/2″ tool at .200″ deep finishes a wall .100″+ wide × .200″ tall, short and rigid, so it won't push away. A 2″-tall wall cut this way acts like a .200″-deep part. Use the most rigid tool (short LOC, minimum wall contact, necked for reach), climb mill, and run Mirror Edge with coolant.
Thin floors
Thin floors have very little thermal mass, so heat distorts them and the cut can start oil-canning. RobbJack's thin-floor geometry reduces oil-canning, residual stress, and heat build-up — it keeps the aluminum's heat treatment intact and eliminates the rubbing and zero-surface-speed problems at the center. It can be added to any tool.
Feather Blend — no mismatch, no hand finishing
On necked tools, a hard step from the cutting diameter down to the neck leaves a mismatch line and a stress riser. RobbJack's Feather Blend smooths that transition, so you avoid the mismatch and the swirl lines that show up when plunging — and skip the hand finishing that usually follows.
Want the numbers proven on your machine?
RobbJack's Tap Testing & Cut Testing service measures your spindle and validates optimized parameters per tool — typically a 30% minimum productivity gain, with chatter engineered out.
See Tap & Cut TestingReal results
- 500%+
- faster cycle times vs conventional tooling
- 41 hr → 1 hr
- aluminum part, prior tooling vs RobbJack
- Max RPM
- chatter-free with Mirror Edge (use coolant)
Keep going
Got a stubborn aluminum part?
Send us the pocket, wall, or floor that's fighting you — we'll spec the tool and the numbers.
Talk to an engineer