Acme-Gridley Type RA Multi-Spindle Bar Machine
Key Specifications
Spindle Configurations
Bar Capacity Range
Drive Type
Typical Cycle Time
Cam Drum Speed
Cross-Slide Capacity
Overview
The Acme-Gridley Type RA is a classic cam-driven multi-spindle bar machine that established the standard for high-volume production of rotational parts throughout the 20th century. With 6 or 8 spindle configurations handling bar stock from 13mm to 76mm diameter, the RA series machines are found in high-volume production environments making automotive parts, plumbing fittings, hydraulic valves, and fasteners. Though cam-driven and analog in nature, the RA series is renowned for its sheer throughput — producing one completed part every revolution of the cam drum, typically 2-8 seconds per part depending on complexity. Many RA machines in service today have been rebuilt and retrofitted with CNC control packages (Tornos C-More, Elk/Acme retrofits) to extend their productive life. The Type RA is among the most widely rebuilt and traded multi-spindle platforms in North America.
Full Specifications
| Parameter | Value |
|---|---|
| Spindle Configurations | 6 or 8 spindle |
| Bar Capacity Range | 13 mm to 76 mm (model-dependent) |
| Drive Type | Cam-driven (mechanical) |
| Typical Cycle Time | 2-8 seconds per part |
| Cam Drum Speed | Adjustable via gear change |
| Cross-Slide Capacity | 6 per spindle position |
| End-Work Tools | Up to 8 per end |
| Spindle Speeds | Multiple preset via gear train |
Specifications sourced from machinetools.com — verified 2026-03-28
Strengths & Limitations
Strengths
- Lowest cost per part for high-volume simple turned parts
- Proven mechanical reliability — many machines run 50+ years
- Large installed base means ready availability of tooling and parts
- CNC retrofit packages available to modernize controls
- High throughput: up to 1,200+ parts per hour for simple parts
Limitations
- Cam changeover takes 4-40 hours depending on part complexity
- Not suitable for small batch or mixed production
- Aging machines may require significant reconditioning
- No CNC flexibility without expensive retrofit
Best For
Frequently Asked Questions
01
New Acme-Gridley cam-type multi-spindles are no longer produced. The Acme-Gridley brand was absorbed into the Hardinge portfolio. The machines in current use are reconditioned, rebuilt, or CNC-retrofitted units. A healthy secondary market exists with specialized rebuilders like Elk-Acme and National Acme who supply parts and rebuilds.
02
The 6-spindle RA handles larger bar diameters (up to 76mm) with more material per part, while the 8-spindle version makes smaller diameter parts (typically up to 50mm) with higher production throughput due to more spindle positions. The choice depends on part diameter and required cycle time.
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