Hardware installation
Threaded inserts, press-fit bushings and bearings, dowels, studs, standoffs, captive nuts, spring pins and rivets, installed with tooling dedicated to the part and torque or force verified where the joint is critical.
Assembly and packaging
Assembly and Packaging Services
Die casting assembly services turn finished castings into ready-to-install components through threaded insert installation, press-fit hardware, gasket and seal fitting, sub-assembly build, leak and function testing, kitting and packaging. CharMax Precision performs this work in the same Dongguan facility that casts, machines and finishes the parts, under one purchase order and one quality record.
In short
Die casting assembly services turn finished castings into ready-to-install components through threaded insert installation, press-fit hardware, gasket and seal fitting, sub-assembly build, leak and function testing, kitting and packaging. CharMax Precision performs this work in the same Dongguan facility that casts, machines and finishes the parts, under one purchase order and one quality record.
The commercial case is straightforward. A casting that ships loose has to be received, inspected, stored and assembled somewhere else, and every one of those steps carries labour, freight and a handling risk. Assembling here removes an entire logistics leg and puts one supplier in front of you when something is wrong, rather than a casting supplier and an assembler pointing at each other.
The engineering case matters more. When the same team casts the boss, machines the hole and installs the insert, the boss geometry is designed for the insert from the start rather than discovered to be marginal at assembly.
Capability at a glance
| Scope | Assembly on castings produced in this facility |
|---|---|
| Insert types | Self-tapping, press-fit knurled, helical coil, key-locking |
| Insert thread range | M2 to M10 |
| Presses | Manual arbor and servo presses to 10 tonnes |
| Press monitoring | Force and displacement curve on critical fits |
| Torque control | Calibrated drivers, 0.2 to 20 N·m, ±5% accuracy |
| Bearing fits | H7/k6 to H7/p6 into machined bores |
| Leak testing | Air pressure decay, 0.5 to 6 bar |
| Leak sensitivity | Detection to 1 cm³/min at 1 bar |
| Packaging | Custom foam, thermoformed tray, blister, carton, export crate |
| Export crates | ISPM 15 heat-treated timber |
| Drop-ship | Neutral packaging direct to your customer or 3PL |
What we assemble onto castings
Assembly work sits between a finished casting and a finished product. The boundary is set by what can be built, tested and shipped reliably from here, and by what genuinely belongs closer to your own final assembly line.
Sealing components
O-rings, moulded gaskets, die-cut foam, adhesive-backed seals, form-in-place dispensed gaskets and EMI conductive gaskets, fitted into cast or machined grooves and verified by leak or ingress testing.
Multi-part sub-assemblies
Housing plus cover plus fasteners, motor mounts with bearings pressed and shimmed, valve bodies with ports fitted, heat sinks with thermal pads applied. Built to your assembly drawing with a documented work instruction per station.
Customer-supplied components
Bearings, seals, connectors, PCBs, labels and branded hardware shipped to us on consignment, received against your part numbers, stored under your lot control and consumed against the build.
Testing and verification
Leak test, torque audit, continuity and bonding resistance, go and no-go gauge checks, and functional fit against a mating part or master gauge you supply.
Identification
Laser marking, pad printing, adhesive labels and cast-in cavity identification, all applied to your artwork and verified for barcode readability before packing.
Threaded insert installation
Threads tapped directly into a cast boss are adequate for most joints. Inserts earn their cost in three situations: the joint is assembled and disassembled repeatedly, the required torque is close to what an aluminum thread will strip, or the boss is too thin to give the 1.5 to 2 diameters of engagement that aluminum needs.
One clarification is worth making because it causes confusion in enquiries. Heat staking, also called thermal insertion, is a thermoplastic process: the tip melts the plastic around a knurled brass insert, which then locks in as the plastic re-solidifies. It cannot be used on an aluminum casting. Where an assembly contains both a casting and a moulded plastic component, we heat stake into the plastic part and use a mechanical insert in the aluminum.
For aluminum, the four practical options are below. All are installed from a machined hole rather than a raw cast hole, because the insert needs a controlled diameter and a square entry face to seat properly.
| Insert type | Installation | Size range | Strength vs tapped boss | Best for |
|---|---|---|---|---|
| Self-tapping steel insert | Torque-controlled driver into a drilled hole, cuts its own external thread | M3-M10 | 2-3× strip torque | The general-purpose choice, serviceable joints in reasonably thick bosses |
| Press-fit knurled insert | Arbor or servo press into a reamed hole, retained by knurl interference | M2-M6 | 1.5-2× strip torque | Thin bosses and small threads where a self-tapping insert would split the wall |
| Helical coil insert | Wound into a tapped oversize hole with a tang tool, tang snapped off | M3-M12 | 2-3× strip torque | High cycle assembly, vibration, and repairing a stripped thread in service |
| Key-locking insert | Pressed into a tapped hole, then locking keys driven into the parent metal | M4-M12 | 3× strip torque, highest rotation resistance | Vibration-critical joints where an insert must not back out |
| Heat-staked brass insert | Heated tip melts surrounding thermoplastic, not applicable to aluminum | M2-M6 | Not applicable | Only the plastic components within a mixed assembly |
Installation torque or press force is set from the insert manufacturer's data, verified on a first-off sample by pull-out or strip-torque test, and monitored on production by audit rather than assumed.
Press-fit hardware, bearings and bushings
Press fits into aluminum castings need the bore machined first. A cast bore carries draft and ±0.1 mm of tolerance, and interference fits do not tolerate that: too little interference and the component turns in service, too much and the boss cracks or the bearing race is distorted enough to fail early. Bores are finish bored or reamed to H7 before anything is pressed into them.
There is a thermal issue specific to aluminum that catches people out. Aluminum expands at about 23 µm per metre per kelvin against steel at 12. An interference fit set at 20 °C loosens as the assembly heats, and a bearing that was correctly retained on the bench can spin in its housing at 90 °C. Where the operating temperature is well above ambient, specify the fit at operating temperature, add a retaining compound, or use a shoulder and circlip so the fit is not carrying the load alone.
Presses are monitored rather than run open loop on anything critical. A force-displacement curve captured during the press stroke detects a misaligned start, a short press, a missing chamfer and a bore that was not machined, all of which look identical once the part is off the press.
- H7/k6 for light interference where the component is also retained mechanically
- H7/n6 for medium interference on typical bushing and bearing seats
- H7/p6 for heavy interference where the fit alone must carry torque or thrust
- Lead-in chamfer of 0.5 to 1 mm at 15 to 20° on the bore, so the component starts square rather than shaving the bore
- Thermal assembly available where interference is high: cooling the steel component or warming the aluminum housing to 100 to 120 °C
- Press force and stroke recorded per part on safety-critical fits, with out-of-window presses segregated automatically
Gasket, O-ring and seal fitting
Sealed housings are one of the most common reasons castings come to assembly, and most sealing failures trace back to the groove rather than the seal. An O-ring needs 15 to 30% compression on the cord to seal reliably, and the groove has to be filled 60 to 85% by volume so the ring has room to deform without being extruded. Those two numbers determine groove width and depth, and they leave very little tolerance for a groove that was cast rather than machined.
Our rule is simple: a soft foam or sponge gasket can sit in an as-cast groove, but an O-ring on a part that must reach IP67 gets a machined groove and a machined sealing land flat within 0.05 mm. It costs one machining operation and removes the most common warranty problem on sealed enclosures.
- O-rings and moulded gaskets fitted into machined grooves, with squeeze verified on a first article cross-section
- Form-in-place polyurethane or silicone gasket dispensed robotically onto the sealing face, ideal for irregular perimeters and enclosures that are opened for service
- Die-cut adhesive-backed foam and rubber gaskets applied with a locating fixture rather than by eye
- EMI conductive gaskets, either fabric-over-foam or conductive elastomer, fitted where a shielded enclosure must maintain a continuous ground path across the joint
- Shaft seals and lip seals pressed into machined counterbores with the correct lip orientation confirmed at the station
- Assembly torque on cover fasteners applied in the sequence specified on your drawing, since an out-of-sequence pattern distorts the sealing face
Leak testing and function testing
Any part that has to hold pressure or keep water out is tested rather than assumed to be sound. Die castings carry some inherent porosity, and machining a face can open an interconnected path that was harmless in the as-cast part, so the test happens after machining and after assembly, not before.
Standard practice is air pressure decay: the cavity is pressurised, allowed to stabilise, then isolated while pressure is monitored over a fixed dwell. It is fast enough for 100% testing in production and sensitive enough for the typical requirement. Where a part fails on interconnected microporosity but is dimensionally good, vacuum resin impregnation seals it without affecting dimensions, and the part is retested afterwards.
| Test | Method | Typical setting | Acceptance |
|---|---|---|---|
| Pressure decay leak test | Sealed cavity pressurised with air, isolated and monitored | 0.5-2 bar, 10-30 s dwell | Leak rate to your drawing, commonly 1-5 cm³/min |
| High pressure leak test | Same method at elevated pressure for hydraulic and pneumatic parts | Up to 6 bar | No measurable decay over the dwell period |
| Immersion bubble test | Part pressurised and submerged, inspected visually | 0.3-0.5 bar | No visible bubble stream, used for first article and troubleshooting |
| Ingress protection check | Water spray or immersion per the stated IP rating | IP65 to IP67 per specification | No ingress after the specified exposure |
| Torque verification | Calibrated driver with torque recorded, or audit with a torque wrench | Per drawing, ±5% | 100% on critical joints, sampling elsewhere |
| Bonding and continuity | Four-wire resistance across the earth path | Per electrical specification | Typically below 10 mΩ across the joint |
| Fit and function gauge | Go and no-go gauges or a customer-supplied master part | Per drawing | 100% on interface features |
Test parameters and acceptance criteria are agreed before production release and written into the control plan. Results are retained by lot and supplied with the shipment where your quality agreement requires it.
Kitting and sub-assembly build
Kitting means shipping a set of related items packed together as one unit rather than as separate line items. For an OEM that removes a picking operation, a stock line and a shortage risk at your end, and it typically costs less here than the labour it displaces at yours.
Sub-assembly build goes a step further: the components are actually assembled and tested, so what arrives is a working module rather than a bag of parts. The decision between the two is usually about how much of your final assembly is proprietary and how much is straightforward mechanical work.
- Matched sets, such as a housing and its own machined cover, kept together by lot where a selective fit exists between them
- Hardware kits with the exact fastener, washer and seal count for one unit, bagged and labelled to your part number
- Component kits combining our castings with your consigned parts under a single kit part number
- Full sub-assembly build to your assembly drawing, with a documented work instruction and station-level quality checks
- Serialised builds where each unit carries a unique identifier linked to its casting lot, test results and assembly record
- Buffer stock of finished assemblies held here against a rolling forecast, so you can call off against short lead times
Packaging, labelling and drop-ship
Packaging is the last chance to protect the work and the first thing your receiving team sees. Machined faces, coated surfaces and fitted seals all damage easily in transit, and a casting that survived every process step can arrive with a scuffed powder coat because it moved 5 mm in a carton for three weeks.
Standard packaging is inner protection sized to the part, an outer export carton and a palletised load. Beyond that, packaging is specified to your standard: your carton artwork, your label format, your pallet dimensions and your barcode data structure. Where you supply a packaging specification we build to it exactly and send photographs of the first pack for approval before the shipment is closed.
- Custom die-cut EPE or EVA foam inserts for high-value parts and machined assemblies
- Thermoformed PET or PS trays for repeat high-volume parts, stackable and returnable where the programme justifies it
- Blister packs and retail-ready presentation where the part goes on a shelf rather than into a factory
- Corrugated dividers, VCI paper and anti-static bags matched to the corrosion and ESD risk of the contents
- Export cartons to 5-ply where sea freight and multiple handling points are involved
- ISPM 15 heat-treated timber crates for heavy or fragile shipments, with the compliance mark applied
- Labelling and barcoding to your standard, including 1D and 2D symbologies, verified for readability before packing
- Neutral drop-ship packaging with no CharMax branding, shipped direct to your customer or 3PL under your documentation
Production evidence
Process details behind this capability
The equipment, controls and finished-part evidence used to deliver this operation in production.
Proof
Related production programs
Real parts we have manufactured that involved this capability.
Keep exploring
Related capabilities and resources
Manufacturing services
Aluminum alloys
Part types
Industries served
Further reading
Frequently asked questions
Can you install threaded inserts in die cast aluminum parts?
Yes, using self-tapping, press-fit knurled, helical coil or key-locking inserts from M2 to M10, installed into machined rather than raw cast holes. Inserts deliver 1.5 to 3 times the strip torque of a thread tapped directly into the boss, which is worth the cost where a joint is assembled repeatedly, carries high torque or sits in a thin boss. Heat staking is a thermoplastic process and cannot be used on aluminum, so in mixed assemblies we heat stake only the plastic components.
Do you leak test die cast housings before shipping?
Yes. Air pressure decay testing at 0.5 to 6 bar is standard for any part with a pressure tightness or ingress protection requirement, run after machining and assembly rather than on the raw casting, since machining can open a porosity path that was sealed by the as-cast skin. Detection reaches 1 cm³/min at 1 bar. Parts that fail on interconnected microporosity but are dimensionally good can be vacuum resin impregnated and retested.
Can you assemble components that we supply?
Yes. Bearings, seals, connectors, PCBs, branded hardware and labels can be shipped to us on consignment, received against your part numbers, stored under your lot control and consumed against the build. We report consumption and remaining stock with each shipment, and we recommend holding two to four weeks of buffer for consigned items, since a shortage of a five cent seal stops a finished assembly just as effectively as a missing casting.
Can you ship assemblies directly to our customer?
Yes. Drop-ship is available with neutral packaging carrying no CharMax branding, shipped to your customer or your 3PL under your documentation, labels and carton artwork. Commercial documents can be issued to your requirements so pricing is not disclosed downstream. We photograph the first pack for approval before the shipment is closed, since a drop-ship consignment is not something you can inspect before your customer sees it.
What packaging options do you offer for export shipments?
Custom die-cut foam inserts, thermoformed trays, blister packs, corrugated dividers with VCI or anti-static protection, 5-ply export cartons and ISPM 15 heat-treated timber crates for heavy or fragile loads. Packaging is built to your specification where you have one, including carton artwork, label format, pallet dimensions and barcode data structure. Where you do not have one, we propose a pack based on part value, surface finish sensitivity and shipping mode.
What is your lead time from purchase order to first parts?
Production tooling takes 25 to 40 days depending on part complexity and cavity count, followed by 5 to 7 days for T1 sample production. After you approve samples, production lead time is 15 to 25 days including machining, finishing and inspection. For repeat orders on existing tooling, expect 15 to 20 days.
Do you have a minimum order quantity?
There is no rigid minimum once tooling exists, and we regularly run batches of 500 pieces. For new programs, the economics rather than a policy set the floor: below roughly 1,000 annual pieces, we will tell you honestly whether CNC machining from billet would serve you better.
How is our intellectual property protected?
We sign your NDA before receiving files and can sign a mutual agreement if you prefer. Your tooling is dedicated to your part and is never used for another customer, your drawings are not shared outside the engineering and production team assigned to your program, and we do not display customer parts or names in marketing material without written permission.
Request for quote
Ship finished assemblies instead of loose castings
Send your assembly drawing and bill of materials. You will get the assembly quoted alongside casting, machining and finishing as one price, with the test plan and packaging specification confirmed before production release.
- Engineering response within 24 hours on business days
- Quotation within 24-48 hours of receiving 2D/3D files
- NDA signed before file review
- Free DFM feedback