Brass Compression Fittings

Brass compression fittings join tube without welding, soldering or flaring: a brass olive (ferrule) is squeezed onto the tube by a nut, forming a leak-tight metal seal that can be undone and remade. Vikay catalogues over 600 compression part numbers covering tees, elbows, connectors, unions, crosses and nipples in metric and BSP sizes.

A compression joint is the fastest reliable connection to make in the field. Cut the tube square, slide on the nut and olive, push the tube home into the body and tighten. The olive deforms onto the tube and against the body taper, and the joint holds without heat, flux or a flare tool.

Vikay's compression range covers straight connectors, male and female elbows, branch and olive tees, four-way crosses, joint nipples, reducing elbows, hose elbows and bulkhead patterns, in male, female and male-by-female thread combinations. Bodies, nuts and olives are turned from free-cutting brass to BS 2874 CZ121 / ASTM B16 C36000. Tube sizes run from 4 mm to 22 mm metric and 1/8 in to 3/4 in fractional; threads are cut to ISO 228 (BSPP), ISO 7/1 (BSPT) or ASME B1.20.1 (NPT).

Typical service is pneumatic and instrument air, LPG and gas appliance lines, lubrication and fuel circuits, and light hydraulic and plumbing work. Part numbers are compositional built from tube size, family code, port size and thread letter, so a full size table sits on each product page. Send the sizes and thread form and we will quote.

Frequently Asked Questions

Do I need a special tool to make a brass compression joint?

No. A square tube cut and two spanners are enough. Deburr the tube end, slide the nut and then the olive onto the tube with the olive's taper facing the fitting body, seat the tube fully in the body and tighten the nut finger-tight plus roughly one to one and a quarter turns. Over-tightening splits the olive and is the usual cause of a weeping joint.

Can a compression fitting be reused after it is undone?

The body and nut can be reused many times. The olive is deformed permanently onto the tube on first tightening, so if you cut the tube back or move the fitting, fit a new olive. Re-making onto the same olive in the same position is normal practice.

What tube can I use with brass compression fittings?

Soft or half-hard copper, brass, aluminium and annealed steel tube in the catalogued outside diameters. The tube must be round, of even wall and cut square. Hard-drawn or thick-wall tube resists the olive and is better served by a flare or twin-ferrule fitting.

What is the difference between BSP parallel and BSP taper on these fittings?

BSP parallel (BSPP, ISO 228) seals on a face or bonded washer at the port; BSP taper (BSPT, ISO 7/1) seals on the thread flanks with sealant or PTFE tape. They share the same thread pitch and will start into each other, which is why mixed joints leak. Confirm the port form before ordering.

How do I read a Vikay compression part number?

Part numbers are compositional: tube size, then the family code, then the port size, then a thread letter, so 10BMCD6N reads as 10 mm tube, BMCD family, 6 port, NPT thread. The size table on each family page lists every reference part number in that family.