Bearing housings and end covers are often treated as “small parts,” but in bevel and spiral bevel drives, they quietly control the things customers complain about most: leaks, noise, inconsistent assembly, and early bearing wear.
At YONGZHU CASTING, we support aluminum die casting for drivetrain components such as bearing housings and end covers, with an export-ready workflow that can include CNC machining, leak testing, and CMM inspection for critical bores.
Fast entry RFQ (recommended): email yongzhucasting@gmail.com with your bearing model (or seat diameter) + tolerance + sealing method + annual volume. If you have a STEP/IGES drawing, include it—if not, we can still start from a 2D drawing or a sample.
What These Parts Do in Bevel & Spiral Bevel Drives
A bevel gearset can be perfectly designed and still perform poorly if the supporting structure shifts under load. Bearing housings and end covers typically do four jobs at once:
- Locate bearings so shaft position stays stable under radial and axial loads
- Hold alignment that affects gear contact pattern (which influences noise and wear)
- Seal lubrication (oil or grease) through faces, grooves, and seal pockets
- Make assembly repeatable so every unit behaves like the approved sample
That’s why sourcing these “smaller” parts is often the easiest way to improve reliability—without changing the gearset.
Parts We Commonly Quote
We regularly quote aluminum die cast parts such as:
- Bearing housings (standalone or integrated bearing-seat structures)
- End covers / side covers (often with bearing seats and sealing faces)
- Bearing caps, seal retainers, closure plates
- Mounting features such as bosses, ribs, and brackets when they are part of the cover/housing geometry
Typical features include bearing bores and shoulders, bolt patterns, locating faces, seal pockets, O-ring grooves, gasket faces, threaded holes, and alignment references.
If your design is still evolving, we can review which features should remain cast-finish and which should be machined—especially around bearing seats and sealing surfaces, where control matters most.
Five Things to Specify for a Quote That Actually Matches Your Assembly
To keep this page practical, here’s what makes the quoting process fast and accurate—without turning your email into a 20-page spec.
The bearing seat requirement
If you can share the bearing model, we can infer key geometry. If you can’t, send the seat diameter and tell us whether the outer ring is intended to be fixed or allowed to float.
The CTQ tolerances
Most drawings have a lot of numbers. In real life, only a few drive performance. Typical CTQs for these parts include:
- bearing bore size tolerance
- roundness / cylindricity (if specified)
- perpendicularity to the locating face
- coaxiality (if there are two bores that must align)
The sealing method
Tell us whether you’re using:
- O-ring groove
- gasket
- sealant joint
- press-fit seal / radial shaft seal pocket
Each sealing method changes how we recommend machining scope and inspection.
The assembly datums
Which face locates the cover to the gearbox? Which features control alignment? This determines fixture strategy and helps maintain repeatability from lot to lot.
The operating environment
Oil vs. grease, temperature, corrosion exposure, and whether the unit sees shock/vibration—these influence alloy selection, wall thickness decisions, and finishing recommendations.
Common Failure Modes and How We Help Prevent Them
These parts fail in predictable ways. If you tell us what you’re trying to avoid, we can shape the DFM and machining plan around that risk.
Leakage at the cover joint
This is usually a combination of sealing face condition (flatness/finish), joint design, and distortion under bolt load. A practical approach is to treat the sealing face as a controlled surface—machined when needed—and to confirm it in a defined test plan if leak tightness is critical.
Bearing bore inconsistency
When bearing seats vary, assembly becomes unpredictable: press-fit feels different unit-to-unit, noise varies, and bearing life scatters. The fix is typically:
- stiffness-aware casting design around the seat (boss + ribs), and
- a stable datum plan for CNC boring/reaming and inspection
Noise and early wear in bevel drives
Bevel gear performance is sensitive to alignment. Even if the gearset is excellent, shifts at bearing seats and locating faces can change shaft position and contact pattern. That’s why these “small parts” deserve CTQ attention—especially for performance-driven applications.
Seal installation issues
Press-fit seal pockets and chamfers matter. If seals are being damaged during assembly, the root cause is often pocket geometry or edge detail—not the seal brand.
CNC Machining and Inspection for Bearing-Seat Parts
We can support CNC machining for the features that most often define fit and sealing:
- bearing bores and shoulders
- sealing faces and locating faces
- bolt holes and threaded holes
- seal pockets and grooves (O-ring/gasket/seal)
Inspection can be matched to your drawing and risk points. For projects where alignment and repeatability are critical, CMM inspection for critical bores can be included.
Here’s a simple way to think about what’s “critical” on these parts:
| CTQ feature | Why it matters | Typical control method |
|---|---|---|
| Bearing seat bore | Fit, life, noise | CNC boring + inspection (CMM optional) |
| Seal pocket / groove | Leakage & assembly | CNC + gauge checks |
| Sealing face flatness | Joint reliability | Face milling + flatness verification |
| Locating face | Repeatable assembly | CNC + dimensional checks |
If you mark the top 3–5 CTQ items in your RFQ, you’ll get a faster and more accurate manufacturing plan.
Finishing and Corrosion Strategy
Some covers/housings live inside an enclosed gearbox and only need functional surfaces; others face outdoor, marine, or washdown conditions where corrosion and appearance matter.
If you already have a coating or surface requirement, include it in the RFQ. If not, tell us the environment and we’ll suggest a practical finishing approach that matches use conditions and budget.
Fast RFQ: The Lowest-Friction Way to Start
Bearing housings and end covers are often the best entry point into a new supply relationship—so we keep the RFQ requirement simple.
Email yongzhucasting@gmail.com with:
- bearing model (preferred) or bearing seat diameter
- tolerance requirement on the seat (and any coaxiality/perpendicularity callouts)
- sealing method (O-ring / gasket / sealant / press-fit seal)
- 2D/3D drawing (STEP/IGES preferred if available)
- annual volume and target lead time
- required machining scope (what must be CNC-machined)
If you only have a sample or an old drawing, send what you have—we can begin with feasibility feedback and a recommended process route.
Need the Main Gearbox Housing Too?
Many projects start with bearing housings/end covers, then expand to the main gearcase once performance and assembly are validated.
If you’re sourcing both:
- Gearbox housing (gear case)
- Bearing housings / end covers
Send them together in one RFQ. We can suggest the most efficient split between casting and machining across the full set, and align leak testing and inspection requirements across the assembly.
FAQ
1) What tolerance class is typical for bearing housing bores (e.g., H7), and what does it mean in numbers?
Many engineering drawings use ISO tolerance classes (ISO 286) for housing bores, and H7 is a common callout. As a concrete example often shown in ISO-based tables, a 50 mm H7 hole can be 50.000 to 50.025 mm (0 to +0.025 mm). Always confirm the final fit based on bearing type, load direction, and operating temperature.
2) Should the bearing outer ring be a press fit or a slip fit in the housing?
It depends on whether the outer ring must be prevented from creeping under load. Press fits are often used when the outer ring tends to rotate relative to the housing (or when loads and vibration could cause movement). Slip/transition fits may be used when thermal expansion, serviceability, or controlled axial movement is needed. The safest way to decide is to specify: bearing type, load direction, expected temperature range, and whether the outer ring must be fixed or allowed to float.
3) What surface finish should I specify for sealing faces (O-ring / gasket) on an end cover?
For many static sealing faces, a commonly referenced target is 32 µin Ra (0.8 µm Ra) max, with tighter finishes often recommended for gas/vacuum or more demanding leakage requirements. The correct finish depends on the seal type (elastomer O-ring vs PTFE/polymer vs metal seal), media, and pressure.
4) What is pressure decay leak testing, and what test details should I specify in an RFQ?
Pressure decay leak testing pressurizes the part, isolates it, and measures pressure drop over time to determine leakage. To make test results comparable across suppliers, specify at least: test pressure, stabilization time, test duration, pass/fail threshold, and whether you’re reporting leakage as pressure drop or as a calculated leak rate.
5) What does “SCCM” mean for leak rate, and why is it used?
SCCM stands for standard cubic centimeters per minute—a common unit for expressing how much gas leaks through a part under standardized conditions. It’s used because it’s intuitive for production thresholds and helps compare results when the same test method and conditions are used.
6) Why do many designs choose aluminum housings/covers instead of cast iron for bearing seats and closures?
A big driver is weight. Aluminum is often cited around 2.7 g/cm³, while cast iron is commonly cited around ~7.2 g/cm³, so aluminum structures can significantly reduce mass in portable equipment, automotive systems, and many industrial assemblies—while still supporting integrated ribs/bosses and complex geometry.
7) Which features should be machined (not left as-cast) on bearing housings and end covers?
If the drawing includes a bearing fit class (like H7), a sealing face finish target (Ra), or GD&T controls (coaxiality/perpendicularity), those surfaces are typically treated as machined CTQ features—especially bearing bores, sealing faces, and locating datums. Casting is excellent for near-net shape and integrated structure; machining is what locks down fit, finish, and repeatability.
8) If an end cover/housing must be pressure-tight, what’s the biggest casting risk to manage?
The most common risk is porosity in sealing or pressure zones, which can turn into leak paths. Managing it usually means aligning on: critical sealing areas early in DFM, consistent wall strategy where possible, appropriate gating/venting approach, machining allowances for sealing faces, cleaning, and a defined leak test method/limit after machining.
