Large-Diameter Deep Hole BTA Drilling for Cylindrical Energy Components

Customer Background

The customer is a heavy equipment manufacturer producing cylindrical components for energy and power systems — hydraulic cylinders, piston rods, large shafts, and pressure-vessel elements. These parts carry large-diameter deep holes (Ø20–100mm) that define flow capacity, assembly fit, and structural integrity.

The Challenge

Large-diameter deep holes in cylindrical components fail on different axes than small-diameter work:

Beyond gun drilling range. Gun drilling is the standard for small diameters, but large holes (Ø20–100mm) need a different process. Drilling these diameters to depth with conventional tooling is slow, wanders, and requires multiple passes.

Depth and straightness at large diameter. Holes to 2,000mm in heavy alloy steel demand continuous chip evacuation and a stable pilot. At Ø50–80mm, tool deflection and vibration — not spindle power — decide whether the hole comes out straight.

Round workpieces need counter-rotation. Cylindrical parts do not sit still under cutting force. Rotating the workpiece against the tool cancels runout and steadies the hole, but not every machine offers it.

Coolant volume, not just pressure. Large-diameter BTA requires high-pressure, high-volume coolant — 80 kg/cm² at 200 L/min — to clear chips from a deep, large-diameter hole. Insufficient flow stalls the process.

One-pass economics. Each hole previously needed multiple operations and setups. The customer wanted large-diameter deep holes done in a single pass, without secondary reaming.

The Solution

RuidCNC supplied the BTA Deep Hole Drilling Machine — a single-spindle BTA drilling system sized for large-diameter deep holes in cylindrical workpieces:

• BTA (single-tube system) drilling Ø20–100mm to 2,000mm — large-diameter deep holes in one pass, beyond gun drilling’s diameter range
• 37 kW heavy-duty spindle at 1,000 rpm — the torque to sustain large-diameter BTA through alloy steel
• Workpiece counter-rotation at 200 rpm — cancels tool runout and stabilizes the hole for straightness
• Workpiece capacity Ø50–150mm — sized for cylindrical energy components
• 80 kg/cm² coolant at 200 L/min — continuous chip evacuation from deep, large-diameter holes
• Single spindle, custom configuration — process built around the customer’s hole program, not a generic machine

Key Machine Specifications

Parameter	Specification
Process	BTA (single-tube system)
Drilling diameter	Ø20 – Ø100 mm
Max drilling depth	2,000 mm
Spindle power	37 kW
Spindle speed	1,000 rpm
Workpiece diameter	Ø50 – Ø150 mm
Workpiece counter-rotation	200 rpm
Coolant pressure / flow	80 kg/cm² / 200 L/min

Results

Metric	Previous Large-Diameter Process	BTA Machine	Improvement
Deep hole straightness	0.25 mm/m	0.06 mm/m	76% better
Hole surface finish	Ra 3.5 µm	Ra 1.5 µm	57% better
Cycle time per hole (Ø60mm × 1,500mm)	3.2 hours	1.4 hours	56% reduction
Tool changes per hole	3–4	1	Eliminated
Scrap from hole deviation	4.2%	0.8%	81% reduction
Max reachable depth	1,000 mm	2,000 mm	2× deeper

Process Validation

The process was validated through:

• Hole straightness and diameter measurement along the full bore
• Surface roughness measurement of drilled holes
• Pressure and flow testing of finished components
• Process capability study (Cpk) across a production batch

Conclusion

The BTA Deep Hole Drilling Machine turns large-diameter deep holes in cylindrical components into a single-pass operation. With BTA drilling to Ø100mm and 2,000mm depth, a 37 kW spindle, and workpiece counter-rotation for straightness, the customer improved hole straightness by 76%, cut cycle time by 56%, and removed secondary reaming from the process. For energy and heavy equipment manufacturers who need large, deep, straight holes, the machine delivers them in one pass.

Figures are representative of typical applications.