SP-2XD Indexable Boring Bar – Precision Boring in Hard Metals, Redefined for 2×D Applications
Boring operations on lathes present a unique set of challenges – especially when machining hardened materials or reaching depths beyond 1.5× the bar diameter. Tool deflection, harmonic chatter, and poor surface finish are frequent obstacles that slow down production and increase scrap rates.
The SP-2XD Hard Metal Indexable Bar from MSK CNC Tools is purpose-built to overcome these barriers. Designed specifically for 2×D depth-to-diameter ratio boring, this bar combines a massive, vibration-absorbing shank with optimised insert geometry to deliver consistent bore quality, even in materials up to 55 HRC.
How the SP-2XD Achieves Superior Boring Performance
Unlike standard boring bars that rely solely on material mass, the SP-2XD incorporates three distinct technologies to suppress vibration and maintain positional accuracy:
Anti-Vibration “Heavy Metal” Shank Construction
The shank is manufactured from a high-density tungsten-heavy alloy (not conventional steel), which provides 1.6× the damping capacity of standard tool steel. This internal friction dissipates cutting energy before it can excite harmonic resonance, ensuring a chatter-free cut even at 2×D extensions.
Negative-Positive Rake Insert Pocket Design
The insert seat is engineered with a unique combination of negative axial rake and positive radial rake. This configuration provides the edge strength needed for hard turning while maintaining a free-cutting action that reduces cutting forces, thereby minimising deflection and improving bore straightness.
Through-Coolant Precision Delivery
Dual high-pressure coolant jets are aimed precisely at the cutting zone – not just the flank, but also the chip-breaker area. This ensures efficient chip evacuation, prevents built-up edge, and maintains thermal stability, which is critical for dimensional control in hard metals.
PRODUCT DESCRIPTION
How WC and SP are classified
SPECIFICATION
SP-2XD vs. Conventional Boring Bars
We tested the SP-2XD against a standard steel-shank boring bar of the same diameter (25 mm) in a turning centre, machining hardened 4140 steel (45 HRC) at 2×D depth. The results are summarised below:
| Performance Metric | Conventional Steel Bar | MSK SP-2XD Bar | Improvement |
|---|---|---|---|
| Bore Taper at 2×D Depth | 0.03 – 0.05 mm | ≤ 0.010 mm | >75% reduction |
| Surface Roughness (Ra) | 1.6 – 2.2 µm | 0.6 – 0.9 µm | Significantly finer |
| Insert Life (per edge) | 6 – 8 min. cutting | 12 – 15 min. | ~2× longer |
| Sound Pressure Level (noise) | 85 – 92 dB | 72 – 78 dB | Quieter operation |
Recommended Applications & Operational Parameters
Workpiece Materials – Hardened steels (up to 55 HRC), tool steels, die steels, stainless steels, and high-temperature alloys
Typical Applications – Hydraulic cylinder bores, mould cavities, bearing housings, and precision bushings where tight tolerances and fine finishes are mandatory.
Recommended Cutting Conditions (starting point for hardened steel):
Cutting speed (Vc): 60 – 120 m/min (adjust based on insert grade)
Feed per revolution (fr): 0.05 – 0.15 mm/rev
Depth of cut (ap): 0.2 – 1.0 mm (finishing: 0.1 – 0.3 mm)
FAQ
A: Yes. The bar accepts a range of inserts with different corner radii and chip-breaker geometries. We offer dedicated roughing (stronger edge) and finishing (sharper edge) inserts that can be swapped easily without removing the bar from the turret.
A: The shank is not solid carbide (which is brittle) nor ordinary steel (which lacks damping). It is a proprietary tungsten-heavy alloy that offers a superior combination of stiffness, toughness, and internal friction, making it ideal for challenging boring operations.
A: No. The SP-2XD has a standard cylindrical shank and fits into any standard lathe boring bar holder or sleeve. However, we recommend a rigid clamping system (e.g., hydraulic or shrink-fit) to maximise performance.
A: Our online Insert Selector Tool (linked below) guides you through a few simple questions about your material and operation type. Alternatively, our application engineers can provide a tailored recommendation within 24 hours.
