Hardinge Quest 8/51 SP
Key Specifications
Chuck Size
Maximum Bar Capacity
Maximum Turning Diameter
Maximum Turning Length
Main Spindle Speed (Max)
Main Spindle Power
Overview
The Hardinge Quest 8/51 SP is a super-precision CNC turning center with sub-spindle capability, representing the most capable configuration in Hardinge's Quest precision lathe family. The SP designation indicates the integrated sub-spindle (pick-off spindle) for complete part processing from bar, eliminating the need for secondary operations on back-face features. The 8-inch chuck and 51 mm bar capacity place the Quest 8/51 SP in the mid-range of Hardinge's precision turning envelope.
The main spindle delivers 15 kW (20 hp) at speeds up to 5,000 RPM with approximately 200 Nm of torque. Hardinge's proprietary bearing preload system maintains spindle stiffness across the full speed range, preventing the thermal drift that can compromise precision on longer production runs. The collet-ready spindle nose accepts 5C and 16C collets directly, delivering 2.5-micron TIR or better at the collet face. The sub-spindle provides 7.5 kW (10 hp) at up to 6,000 RPM, capable of back-turning, back-boring, and back-drilling to complete parts in a single cycle.
The machine is built on Hardinge's one-piece cast iron slant bed with hardened and ground box ways. The 12-station turret accommodates VDI or BMT tooling with live tooling capability, and C-axis is available on both main and sub-spindle for positioned milling operations. X-axis travel of 200 mm and Z-axis travel of 500 mm provide a generous turning envelope for the 51 mm bar class.
The Quest 8/51 SP runs on Fanuc 0i-TF Plus control and targets the same precision manufacturing segments as the legendary Hardinge CHNC — medical devices, aerospace components, defense ordnance, and any application where the combination of sub-spindle complete processing and Hardinge-level concentricity justifies the premium price point.
Full Specifications
| Parameter | Value |
|---|---|
| Chuck Size | 8 in (203 mm) |
| Maximum Bar Capacity | 51 mm (2.0 in) |
| Maximum Turning Diameter | 280 mm (11.02 in) |
| Maximum Turning Length | 500 mm (19.69 in) |
| Main Spindle Speed (Max) | 5,000 RPM |
| Main Spindle Power | 15 kW (20 hp) |
| Main Spindle Torque | 200 Nm (148 ft-lb) |
| Sub-Spindle Speed (Max) | 6,000 RPM |
| Sub-Spindle Power | 7.5 kW (10 hp) |
| Spindle Concentricity | 2.5 microns TIR at collet face |
| Travel X | 200 mm (7.87 in) |
| Travel Z | 500 mm (19.69 in) |
| Turret Stations | 12 (VDI/BMT, live tooling capable) |
| C-Axis | Main and sub-spindle |
| Guideway Type | Hardened and ground box ways |
| Rapid Traverse X | 20 m/min (787 ipm) |
| Rapid Traverse Z | 24 m/min (945 ipm) |
| Control | Fanuc 0i-TF Plus |
| Machine Weight | 4,200 kg (9,259 lb) |
Specifications sourced from hardinge.com — verified 2026-03-28
Strengths & Limitations
Strengths
- Integrated sub-spindle enables complete part processing from bar, eliminating secondary operations and part handling for back-face features
- Hardinge super-precision spindle delivers 2.5-micron TIR at the collet face, setting the standard for concentricity in production turning
- C-axis on both main and sub-spindle enables complex positioned milling operations on both ends of the part
- Box way construction provides superior vibration damping for consistent surface finish quality across long production runs
- 15 kW main spindle with 200 Nm torque handles productive cutting in stainless steel and titanium at full 51 mm bar capacity
- 12-station turret with live tooling provides enough tool positions for complete mill-turn processing of complex small parts
Limitations
- Premium price point of $150K-$225K places the Quest 8/51 SP above many competitors in the 51 mm bar class
- 51 mm bar capacity limits the machine to small-to-medium diameter work; larger parts require the Quest 10/65
- Box way rapid traverse is slower than linear-guideway machines, adding non-cutting time in high-volume production
- Hardinge's corporate restructuring creates uncertainty around long-term service and parts support in some regions
Best For
Frequently Asked Questions
01
SP stands for Sub-spindle Precision, indicating the machine includes an integrated pick-off sub-spindle for back-face operations. This enables complete part processing from bar: the main spindle machines the front features, the sub-spindle picks off the part and machines the back face, and the finished part drops into the parts catcher — all in a single automated cycle.
02
Both are sub-spindle precision turning centers from Hardinge, but the Quest 8/51 SP is a newer-generation platform with updated spindle technology, 51 mm bar capacity (vs 42 mm on the T42SP), more spindle power (15 kW vs 15 kW main), and a larger turning envelope. The Quest commands a higher price but delivers more capability and updated features.
03
Sub-spindle processing eliminates manual part flipping and rechucking, which typically saves 30-120 seconds per part depending on complexity. On production runs of 500+ parts, this translates to significant daily output increases. The sub-spindle also eliminates the concentricity error introduced by manual rechucking, improving part quality.
04
Yes, with a bar feeder, parts catcher, and appropriate CNC program, the Quest 8/51 SP runs fully unattended for lights-out production. The sub-spindle pick-off and automatic part delivery to the parts catcher eliminate all manual intervention during the production cycle. Typical unattended run times depend on bar length and part cycle time.
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