Pressed-Fit Closures for Bore Openings
Durus metric end caps plug or close a housing bore where no shaft penetrates. The nitrile rubber coating on the outer diameter provides an improved press-fit seal compared to bare-metal caps, accommodating bore tolerance variations and providing corrosion resistance. 64 metric sizes from 19mm × 7mm up to 240mm × 15mm.
What Are Metric End Caps?
A metric end cap (also called an expansion plug or blind plug) is a stamped steel cup with a rubber-coated outer diameter, designed to press into a housing bore that needs a permanent closure. End caps install where a bore exists in the housing but no shaft passes through - typical applications include unused output shaft positions on multi-output gearboxes, expansion bore closures in cast iron housings, and capping of inspection or fill ports that need a permanent seal.
The nitrile rubber coating on the OD provides three benefits: it accommodates slight bore tolerance variations (a bare-metal cap requires more precise bore machining), it provides a corrosion barrier between the steel cap and the housing material, and it creates an improved compression seal that is less prone to leakage than a bare metal interference fit.
CAP vs CAP4 Profile
Durus offers two end cap profiles, selected by the available depth in the housing:
| Profile | Shape | Best For |
|---|---|---|
| CAP | Standard depth | Standard housings with adequate cavity depth - the most common selection |
| CAP4 | Shallow profile | Housings with limited cavity depth where a standard CAP would protrude or bottom out |
The part number format identifies the profile: 100X10 CAP is a 100mm bore × 10mm depth standard cap; 115X12 CAP4 is a 115mm bore × 12mm depth shallow cap. Match the profile to what fits the housing cavity.
Size Range
Durus metric end caps cover bore diameters from 19mm to 240mm. The full part number table is on the end cap product spec sheet - every product page links to the complete catalog reference.
When to Use End Caps
- Unused gearbox output position - Multi-output gearboxes often have unused shaft positions that need permanent closure
- Casting expansion bores - Sand-cast housings have core-pull bores that need to be sealed after casting
- Inspection port closure - Some equipment has temporary inspection ports that get capped after factory inspection
- Retrofit closure - Modifying equipment that previously had a shaft penetrating a position that's now sealed off
Related Products
Frequently Asked Questions
What is a metric end cap used for?
A metric end cap presses into a housing bore that needs a permanent closure but does not have a rotating shaft passing through. Common uses include closing unused output shaft positions on multi-output gearboxes, sealing expansion bores left from sand casting, capping inspection or fill ports after factory testing, and retrofit closure of bore openings when equipment is modified. The nitrile rubber OD coating provides a leak-tight seal in the housing material.
What is the difference between a CAP and a CAP4 end cap?
The CAP profile is the standard depth used in most applications. The CAP4 profile is a shallower variant for housings with limited cavity depth where a standard CAP would protrude past the housing face or bottom out against an internal feature. Both profiles install the same way (press-fit) and provide the same sealing function. Match the profile to the available depth in the housing - measure cavity depth before ordering if unsure.
How do I install a metric end cap?
Clean and lubricate the housing bore lightly with installation grease. Position the end cap squarely at the bore opening with the rubber-coated outer diameter against the bore wall. Press the cap into the bore using a flat-faced installation tool sized to match the cap outer diameter - drive the cap until the outer face is flush with or slightly recessed from the housing face. Avoid striking the cap directly with a hammer, which can deform the metal cup and compromise the seal.
What sizes do metric end caps come in?
Durus metric end caps range from 19mm bore × 7mm depth up to 240mm bore × 15mm depth, covering 64 standard sizes. The part number directly encodes the dimensions: 100X10 CAP is a 100mm bore × 10mm depth cap. The most common stocked sizes match standard metric bearing bore dimensions used in industrial gearboxes and pump housings. View the complete size table on any end cap product page.
Can a metric end cap be reused?
No. Metric end caps are designed for single-use press-fit installation. Removing an installed cap typically deforms both the cap and the rubber coating, breaking the seal. If the cap must be removed for any reason - typically for equipment service that requires reopening the bore - install a new cap upon reassembly. End caps are inexpensive enough that single-use replacement is the standard practice.
Cross-reference from any CR, SKF, National, Federal-Mogul, or Timken part number. Houston, TX warehouse stocks the full Durus catalog with same-day shipping for in-stock items.
Call (888) 203-2358 or email sales@texasbelting.com with your existing part number, equipment make/model, or shaft and bore measurements.
