CNC lathes for fittings and connectors: why a connector is a turned part

Almost every fitting in a hydraulic, pneumatic or plumbing assembly is a turned part. The geometry — round, threaded at both ends, hollow, with a hex in the middle — is what a lathe does better than anything else.

Look at any fitting, coupling or connector and you are looking at a rotationally symmetric body: a bore down the middle, a thread at each end, a hexagon or knurl to grip, and often a sealing cone. Turn it in your hand and it becomes obvious why these parts are made on a lathe and not on a machining centre. Everything that matters is concentric with one axis.

One setup, one axis, no stack-up

The value of turning a fitting rather than milling it is that the bore, both threads and the sealing cone are all produced from the same rotational axis, in one clamping. Nothing has to be re-located. On a machining centre the same part needs at least two setups, and each setup adds its own error to the ones already there.

The features that decide the price

• The through bore. Long, small-diameter bores are the slowest feature on the part. A designer who can accept a slightly larger bore often halves the drilling time.
• The threads. Rolled where the material allows — faster, stronger, no chips. Cut where the geometry or the standard demands it.
• The sealing cone. Usually the tightest requirement on the drawing, and the reason the part is inspected at all.
• The hexagon. Milled with live tooling in the same cycle. Adding it is cheap; adding it in a second operation is not.

Materials

Brass for most plumbing and pneumatic fittings, free-cutting steel for machine building, stainless for anything exposed or hygienic. Brass gives the best surface and the longest tool life; stainless the longest cycle time. The choice is usually made by the medium and the environment, not by us — but if a drawing specifies a difficult material for a non-critical part, we say so before quoting.

We turn fittings from Ø 2 to Ø 52 mm in series from 5,000 pieces. See the parts we make or send the drawing to info@kovinski-izdelki.si.