Nut crimping: why the NC series is a separate class of machine
The swivel nut of a fitting must rotate freely — and never come off. We explain how it is retained by flaring the nipple edge, why a regular press does not suit the operation, and how the LT-NC series covering 10–116 mm is built.
On most threaded hose fittings the nut is a swivel one: it rotates freely on the nipple, and during installation only the nut is tightened while the hose does not twist. The arrangement is simple: the nut is placed on the nipple, and then the nipple edge is flared into a collar — it reaches behind the nut face and retains it without clamping. The operation is called nut crimping, and it is exactly what NC-series machines do. This is equipment not for a service centre but for those who produce fittings and adapters in series.
How the nut is held on the nipple
The requirements are contradictory, as in any flaring. Crimp too little — the collar is small and the nut eventually comes off under vibration. Crimp too much — the collar presses the nut, it stops rotating or turns stiffly, and the fitting is rejected at assembly. The force is applied to a narrow annular band a few millimetres wide, evenly around the circumference — otherwise the nut is skewed.
Why a regular press does not help here
The dies of a P-series crimping press are designed for a hose ferrule: their working length is tens of millimetres, and the force is spread along the whole joint. Edge flaring needs the opposite — a short working zone and a precise annular crimp. That is why the NC series has its own dies with a working length of 3 to 9 mm: all the machine's force is concentrated on the edge band.
The second reason is pace. A fitting manufacturer counts seconds per part, not minutes: the NC cycle is 1.5–1.9 seconds per 10 mm of stroke, with semi-automatic and automatic modes and a foot pedal included. On a long run of one size the automatic mode repeats the cycle without the operator.
The LT-NC series: three machines for 10–116 mm
| Model | Crimping range | Dies | Cycle 10 mm | Power 3/1 phase |
|---|---|---|---|---|
| LT-NC20 | 10–49 mm | NC20 (L 3–5 mm) | 1.5 s | 3.0 / 4.0 kW |
| LT-NC30 | 45–87 mm | NC30 (L 5–7 mm) | 1.9 s | 4.0 / 5.5 kW |
| LT-NC40 | 10–116 mm | NC20 / NC30 / NC40 | 1.9 s | 4.0 / 5.5 kW |
The force of all three is 1450 kN. The LT-NC20 covers common nuts up to 49 mm with the fastest cycle; the LT-NC30 takes large sizes up to 87 mm; the LT-NC40 is the universal machine, accepting dies of all three series and covering the full range from 10 to 116 mm. Dies are assembled into a set for Your range: the basic ones are included, while the asterisked positions in the tables are non-standard and supplied separately to order.
Where it is used
- Production of fittings and adapters — the main field: serial assembly of DKO, JIC and BSP swivel fittings, where the nut is placed on the nipple.
- Assembly of adapters and quick couplings — retaining swivel and locking elements by flaring.
- Annular flaring of short parts — wherever a precise crimp of a narrow band is needed: bushings, retaining rings, caps.
A hose shop needs an NC machine when it outgrows hose assembly and starts making its own fittings — the rest of the chain is covered in the article on setting up a shop; why the working face of any die must stay mirror-smooth is the subject of the article on dies.