Dual-Spindle Gun Drilling Reduces Cycle Time for Crankshaft Oil Holes

Customer Background

Our customer is a Tier 1 automotive powertrain manufacturer supplying crankshafts to major OEMs in Europe and North America. With increasing production targets for next-generation engine platforms, they needed to raise the throughput of crankshaft oil hole drilling while holding strict quality standards.

The Challenge

Crankshaft oil holes present demanding gun drilling requirements:

Angled, intersecting geometry. Oil holes are drilled at acute angles (typically 15–30°) into the crank pin journal surface, intersecting pre-existing galleries. Any positional error can compromise engine lubrication and lead to failure.

Short, precise, high-quantity holes. These surface-entry oil holes are drilled to a maximum length of 50mm — short, but drilled in quantity across every journal and pin, so per-hole cycle time drives throughput.

Hardened material. Crankshafts are forged from 4140 or manganese steel hardened to 45–52 HRC. High hardness and low thermal conductivity cause rapid tool wear — conventional gun drill life averaged only 60 parts between resharpening.

Burr control. When gun drills break through into the pre-cast oil gallery, burrs can dislodge and block the oil duct. Deburring these internal locations is difficult.

Production volume. The customer required 600+ crankshafts per day, each with 4–6 oil holes — over 3,000 deep holes daily.

The Solution

After a thorough process analysis, RuidCNC engineered the Two Spindles Crank Shaft Gun Drilling Machine (RD500-C2) for crankshaft oil hole production:

• Two independent 11 kW spindles — two oil holes drilled simultaneously, cutting per-hole cycle time in half
• Crankshaft-specific fixture with guide bushings — the bushing supports the drill at the hole entry, holding the angled start point accurately before the drill engages the journal
• 15 kW servo high-pressure oil pump — consistent gun drilling oil pressure for reliable chip evacuation from short, angled holes
• 27 N·m Z-axis torque — stable feed through hardened journals without wander
• Siemens Sinumerik 828D control — programmable angled hole patterns across the crankshaft

Key Machine Specifications

Parameter	Specification
Spindle configuration	2 (simultaneous, 11 kW each)
Drilling diameter	Ø10 – Ø25 mm
Max drilling length	50 mm
Z-axis torque	27 N·m
High-pressure oil pump	15 kW servo
CNC control	Siemens Sinumerik 828D
Workholding	Crankshaft fixture with guide bushings

Results

After installation and production ramp-up, the two-spindle machine delivered the following results:

Metric	Previous Process	Two-Spindle Machine	Improvement
Cycle time per hole	45 seconds	27 seconds	40% reduction
Holes per day (single shift)	640	1,066	66% increase
Tool life (parts between regrinds)	60	85	42% improvement
Hole position accuracy	±0.02 mm	±0.01 mm	50% better
Scrap from oil hole position errors	2.1%	0.4%	81% reduction
Machine uptime	—	94%	Reliable

Process Validation

The process was validated through:

• Hole position and angle measurement on a CMM
• Oil gallery flow and pressure testing of finished crankshafts
• Burr inspection at gallery break-through points
• Process capability study (Cpk) across a production batch

Conclusion

The two-spindle crankshaft gun drilling machine solves crankshaft oil hole production by combining dual-spindle throughput with angle guidance. With two holes drilled simultaneously, a guide-bushed fixture that locks the angled entry, and a 15 kW servo oil pump for reliable chip evacuation, the customer cut per-hole cycle time by 40%, increased daily output by 66%, and reduced scrap from oil hole position errors by 81%.

Figures are representative of typical applications.