Wexmar provides custom end cap and plug machining for housings, tubes, cylinders, manifolds and pressure vessels. Our Canastota, New York shop produces CNC machined end caps, threaded plugs, port plugs, covers and closures on CNC lathes, Swiss-type machines and horizontal machining centers. These parts look simple, but a sealing face, an O-ring groove or a thread callout usually carries a pressure rating, and we treat them accordingly.
What end caps and plugs do and who buys them
End caps and plugs close an opening, retain an internal component, locate a bearing or seal a pressure boundary. Typical buyers include:
- Fluid power, pump and valve OEMs needing port plugs, cylinder caps and covers
- Instrumentation and sensor makers needing threaded housings and closures
- Tube, roller and enclosure builders needing machined end caps
- Defense and government programs with build-to-print closures
How our custom end cap and plug machining works
CNC lathes
Most end caps and plugs are turned on our Mazak and Doosan lathes. The thread or pilot, sealing face and O-ring groove are finished in one chucking so the seal sits square and concentric to the thread. Live tooling adds hex flats, spanner holes, cross drills and bolt circles. The Mazak Multiplex 6300Y completes both faces in one cycle for production. See CNC turning.
Swiss machining
Small port plugs, bleed screws and closures up to 32 mm diameter run on our Maier MLK-32 Swiss-type machines with bar feeders, often lights-out for high volumes.
Horizontal milling
Square and rectangular covers, flanged end caps with non-round bolt patterns and caps with side ports are machined on our Mazak horizontal machining centers. See CNC milling.
Typical materials
- Carbon and alloy steel for hydraulic plugs and caps, usually plated
- 303, 316 and 17-4 PH stainless for corrosive, sanitary and marine service
- 6061 aluminum for lightweight end caps, often anodized
- Brass and bronze for fittings and low-pressure plugs
- Inconel and Monel for high-temperature and chemical service
- Engineered plastics for insulating or chemical-resistant closures
Critical features and how we hold them
- O-ring groove: dimensioned to the seal standard, with controlled side wall finish and corner radii.
- Sealing face flatness and finish: faced with a finish pass and checked for flatness and lay.
- Thread class and perpendicularity: threads are gaged to class and cut square to the sealing face.
- Pilot fit: pilot diameters are held to the mating bore fit for alignment.
- Bolt hole position: positioned from the pilot axis so caps install without binding.
Typical tolerances and finishes
| Feature | Typical tolerance | Tighter on request |
|---|---|---|
| Pilot diameter | +/-0.001 in | +/-0.0005 in |
| O-ring groove diameter and width | +/-0.002 in | +/-0.001 in |
| Sealing face flatness | 0.001 in | 0.0005 in |
| Thread | Class 2A / 2B, NPT L1 | Class 3A / 3B |
| Bolt hole true position | 0.005 in | 0.002 in |
| Sealing surface finish | 32 to 63 Ra | 16 Ra |
Values are typical. Diameter, wall thickness and material affect what is practical, and the quote confirms each callout.
Design notes
Name the seal standard, such as AS568 O-rings or SAE J1926 straight thread ports, so groove and spot face dimensions are unambiguous. A thread relief at the sealing shoulder helps the plug seat fully. If a cap will be anodized or plated, state whether the thread class applies after finish. For thin covers, stock and fixturing matter for flatness, and we will flag anything that may move after machining.
Secondary operations
Zinc and nickel plating, black oxide, anodizing, passivation and heat treat are completed through qualified outside processors. Pressure testing requirements can be discussed at the quote stage.
Quantity patterns
End caps and plugs are often high-count parts, from a few hundred to tens of thousands per year, released on blanket orders. Prototype quantities of 10 to 50 are also common, and bar stock can be held for scheduled releases so repeat orders ship quickly with consistent material. Related parts include pistons and cylinders.
Inspection
Threads are gaged to class, grooves are checked on the Mitsubishi optical comparator, and flatness and position are verified on our Brown and Sharpe CMMs. FAI in AS9102 format, material certs and heat-lot traceability are available.
Getting a quote
Send the drawing, seal and thread callouts, material and quantity. You can upload a drawing for an instant estimate, and an estimator will confirm price and lead time. Call (315) 400-2654 with questions.