Fitting insertion: why the fitting resists and what the LT-IN2 is for
Between skiving and crimping there is an operation people remember when their shoulders ache: seating the fitting in the hose. We look at why on large diameters the fitting is physically hard to insert, what is wrong with the mallet — and how an insertion machine solves it with compressed air.
On small-diameter hoses the seating of a fitting goes unnoticed: wet it, twist it, push it home by hand. But as the diameter grows, the contact area between the rubber and the tail grows with it, and at 1"–3" this "unnoticeable" operation turns into weightlifting. In the shop process chain it sits right before crimping — and this is where the mallet, the hose clamped in a vice and the operator hammering the fitting most often appear.
Why the fitting resists
The reason is not clumsy hands but the arithmetic of tolerances. Hose standards — EN 853/856 and those harmonised with them — set the bore with a tolerance band: fractions of a millimetre, growing with the diameter. Fitting tails are not identical either: the barb profile and diameter differ between manufacturers within their own tolerances. While both dimensions sit mid-band, the seating is tolerable. But a hose at the lower limit plus a "full" tail — and the interference adds up to a force a hand can no longer produce. Hence the familiar paradox: the same pair "sometimes goes in, sometimes doesn't" from batch to batch.
Straight fittings are indeed driven in with a mallet in production — the method works, but with three reservations. The blows land on the thread and sealing surfaces. The fitting often stops just short of full depth, and incomplete seating is a hidden defect: the ferrule is crimped over only part of the reinforcement length, invisible from outside. And above all — 45° and 90° elbow fittings cannot be seated with a mallet at all: there is nothing to strike along the nipple axis, and blows on the body bend and damage it.
How the insertion machine works
The LT-IN2 replaces blows with smooth pressing. The hose is fixed by a clamp with up to 4 kN of force, the fitting is set into the tool — and the air cylinder drives it strictly along the hose axis with up to 6.2 kN, to the stop. No impacts: the force builds smoothly, the seating is controlled, and an elbow fitting goes in as easily as a straight one because the force is transferred by the tool coaxially with the nipple.
| Parameter | Value |
|---|---|
| Hose diameter | up to 3" (OD up to 100 mm) |
| Insertion / clamping force | 6.2 / 4 kN |
| Supply | compressed air, up to 8 bar |
| Tooling | IN-0…IN-54 sets for the fitting range |
| Dimensions / weight | 650×430×400 mm · 105 kg |
The tooling is selected for Your fittings — like the press dies, it is a set for a specific range, not universal tooling.
Who needs it
- Small-series and serial production. When there are dozens and hundreds of assemblies per shift, fitting insertion consumes the operator's time and strength more than any other manual operation. The machine evens out the pace and takes the load off people.
- Large diameters and heavy hoses. Spiral 4SP/4SH/R13/R15 after skiving are assembled with interlock fittings of large sizes — exactly the case where hands are no longer enough; the types themselves are covered in the hose guide.
- Ranges with elbow fittings. Mobile-machinery hydraulics is full of 45° and 90° elbows — the machine seats them properly, not "as it happens".
Maintenance: next to none
There are no electronics and no hydraulics in the machine — only pneumatics from the shop air line. Two requirements: prepared air (a water separator and filter in the line, as for any air tool) and attention to the air cylinder seals — it is a maintenance-free unit whose seals are replaced as they wear, on a timescale of years. Against the schedule of a crimping press, the insertion machine is the most carefree member of the chain.