Die Cast Gearbox Housings

Gearbox housings are among the most technically demanding aluminum die casting applications. They must maintain bearing bore alignment under sustained load (affecting gear mesh and noise), seal lubricating oil over years of service, and withstand shock loading from reversals and overloads.

KastMfg produces gearbox and reducer housings for worm, helical, bevel-helical, and right-angle gear configurations. Paired bearing bores are machined in a single HMC setup to maintain center distance and parallelism across all production units.

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Housing Types

Type	Gear Configuration	Typical Ratio
In-line helical	Parallel shaft	1.5:1 -20:1
Worm reducer	Worm/wheel	5:1 -100:1
Right-angle helical	Bevel-helical	1.5:1 -40:1
Planetary carrier	Planetary	3:1 -50:1
Servo gearhead	Precision planetary	3:1 -100:1

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Critical Dimensional Requirements

Parameter	Specification
Bearing bore center distance	±0.03-0.05 mm
Bore parallelism	0.02 mm/100 mm
Bore diameter (H6/H7)	±0.008-0.020 mm
Parting face flatness (oil seal)	0.02 mm
Oil fill/drain thread	Go/no-go gauge verified

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Material

A380 standard · A380 + T5 for high-load applications · A360 for outdoor/humid industrial environments · ADC12 for Japanese OEM programs

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Manufacturing

Single-setup HMC machining maintains center distance. Parting faces face-milled to 0.02 mm flatness for liquid gasket or defined-compression O-ring sealing. Oil fill, drain, and vent ports drilled and tapped to drawing specification.

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Applications

Industrial conveyor and material handling drives · Agricultural equipment drives and PTO gearboxes · Construction equipment power transmission · HVAC fan drives · Servo gearheads for robotics

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Gearbox housing inquiry: yaoqingpu1983@gmail.com | +86 138 1403 4409 | No.6, Rungu Road, Nanjing, China

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Why Single-Setup Machining Matters for Gearbox Housings

The most critical quality parameter in a gearbox housing is not any individual bore tolerance -it is the relationship between paired bores. A worm gear housing with input shaft bore at 25.000 mm diameter and output shaft bore at 30.000 mm diameter, each individually within H6 tolerance, but with center-to-center distance 0.15 mm short of specification, will produce a gearbox with incorrect gear mesh -high noise, reduced efficiency, and short service life.

KastMfg's horizontal machining center (HMC) setup for gearbox programs positions both bearing bore locations in a single fixture, machining them in sequence without repositioning. The bore-to-bore relationship -center distance, parallelism, angular orientation -is controlled by the machining program and fixture, not by the accumulation of individual setups.

Achievable with single HMC setup:

• Center distance: ±0.025-0.040 mm
• Bore parallelism: 0.015-0.025 mm per 100 mm
• Angular alignment between shafts: ±0.1°

These are production specifications across hundreds of castings, not first-article results. Statistical process capability (Cpk) on center distance: typically 1.6-2.1 in KastMfg's established gearbox programs.

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Oil Sealing -Parting Face Flatness

A gearbox housing parting face must seal lubricating oil -typically gear oil with EP additives -over years of service in an industrial environment. The sealing system (liquid gasket, paper gasket, or O-ring) defines the required parting face flatness:

Sealing Method	Required Face Flatness	KastMfg Achieves
Liquid gasket (Loctite)	0.05-0.10 mm	0.02 mm after face mill
Paper gasket	0.10-0.25 mm	0.02 mm -exceeds requirement
O-ring (groove machined)	0.02 mm flatness at O-ring seat	0.01-0.02 mm

All gearbox parting faces at KastMfg are face-milled after casting, regardless of sealing method. As-cast flatness of 0.1-0.3 mm is inadequate for any gearbox sealing application -the machining step is not optional.

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Oil Lubrication Provisions

Every gearbox housing requires: oil fill port, oil level indicator port, oil drain, and breather/vent. Standard provisions:

• Fill and drain: drilled and tapped M16x1.5 or M20x1.5 (metric) or 1/4"-18 NPT (inch)
• Breather: M12x1.5 or 1/8"-27 NPT
• Level plug: M16x1.5 or sight glass boss

These are drilled, tapped, and gauged as part of the standard CNC machining scope on gearbox programs. Custom port configurations per customer drawing are accommodated.

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Gearbox Housing Surface Treatment

Application	Standard Finish	Notes
Indoor industrial drives	Shot blast + powder coat (RAL 7035 light gray standard)	Color indicates gear oil grade in some OEM conventions
Outdoor drives (rain exposure)	Shot blast + e-coat primer + powder coat	E-coat ensures coverage on internal cavity surfaces
Food processing industry	Shot blast + electropolish or clear anodize (A360 alloy required)	FDA-compliant finish
Wet/wash-down environments	A360 + e-coat + epoxy topcoat	Chemical resistance to cleaning agents

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Gearbox housing inquiry: yaoqingpu1983@gmail.com | +86 138 1403 4409 | No.6, Rungu Road, Nanjing, China