Technical Guide

Crimping Guide

Get the Crimp Right Every Time

The complete guide to hydraulic hose crimping: correct crimp diameter, ferrule selection, skive vs no-skive, crimp measurement, and common mistakes that cause leaks.

Ask for Help ← All Technical Guides

How to Crimp Hydraulic Hose

Correct crimping is critical for a leak-free, safe hose assembly. Follow these steps in order.

Select the Correct Ferrule and Fitting

The ferrule (outer sleeve) and fitting (insert) must match the hose type and dash size. Using the wrong ferrule is a common cause of blow-offs. Match: hose type (R1AT/R2AT/4SP/4SH) + dash size + skive or no-skive.

Cut the Hose Cleanly

Use a proper hose cutting machine or fine-tooth saw. A clean, square cut is essential. A jagged or angled cut prevents the fitting from seating properly and can introduce debris into the hydraulic system.

Skive If Required

Skiving removes the outer cover (and sometimes inner tube) at the fitting area. No-skive ferrules don't require this. Skive ferrule: remove the outer cover to expose the wire reinforcement. No-skive ferrule: crimp directly over the cover. Check which type your ferrule requires.

Mark the Insertion Depth

Mark the hose where the fitting insert will fully seat. Push the fitting insert into the hose until it stops — the fitting must be fully inserted so the ferrule crimps over the correct area. Incomplete insertion is a common cause of leaks.

Crimp with the Correct Die Set

Select the die set for your hose and fitting. The die closes to a specific diameter — this is the crimp diameter. Use the manufacturer's crimp chart for the exact crimp diameter for your hose-fitting combination. Never guess.

Verify the Crimp Diameter

After crimping, measure the ferrule OD at the crimp point with a caliper (or crimp gauge). Compare against the manufacturer's specification. If it's outside tolerance, adjust the die and re-crimp on a new assembly. Record the measurement.

Technical Specifications

R1AT / 1SN Crimp	Single wire braid. Ferrule crimped directly over braid (skive) or cover (no-skive). Typical crimp OD for -6 (3/8″): ~25-27mm.
R2AT / 2SN Crimp	Double wire braid. Requires higher crimp force. Crimp OD slightly larger than R1AT for same dash size.
4SP / 4SH Crimp	Four spiral wire. Very stiff — needs heavy-duty die sets. Crimp diameter is critical; too loose causes blow-off.
R13 Crimp	Six spiral wire. Highest pressure. Requires dedicated crimp settings. Do not interchange with 4SH settings.
Skive vs No-Skive	Skive: cover removed before crimp. No-skive: crimp over cover. Ferrule type determines method.
Crimp Diameter Tolerance	Typically ±0.1mm to ±0.2mm. Beyond tolerance = leak or blow-off risk.
Measurement Tools	Digital caliper or crimp gauge. Measure ferrule OD at the crimp point.
Crimp Chart Source	Hose manufacturer's data sheet or crimp chart (per hose type and dash size).

Why Crimp Diameter Matters

The crimp diameter is the single most important parameter in hose assembly. Here's what happens when it's wrong: Too tight (under-crimped diameter): - The ferrule bites too deep into the hose cover and reinforcement - The wire reinforcement can be damaged or cut - The hose may fail prematurely at the crimp point - The inner tube may be crushed, restricting flow Too loose (over-crimped diameter): - The ferrule doesn't grip the hose sufficiently - Under pressure, the fitting can blow off the hose - This is a serious safety hazard Correct crimp diameter: - The ferrule grips the hose cover and reinforcement securely - The inner tube is not crushed - The assembly retains full working pressure with a safety margin Always use the manufacturer's crimp chart. Crimp diameter varies by hose type (R1AT vs R2AT vs 4SP), dash size, and ferrule type. A crimp diameter that works for R1AT may be wrong for R2AT even at the same dash size.

Common Crimping Mistakes

1. Using the wrong die set: Each hose-ferrule combination needs the correct die. Using the wrong die produces the wrong crimp diameter. 2. Not verifying with a caliper: Visual inspection is not enough. Always measure the crimp diameter. 3. Incomplete fitting insertion: If the fitting insert isn't fully seated, the ferrule crimps over the wrong area — leaks result. 4. Mixing skive and no-skive: A skive ferrule over a no-skive hose (or vice versa) produces an unreliable crimp. 5. Ignoring the crimp chart: Guessing the crimp diameter is dangerous. Always reference the manufacturer's chart. 6. Crimping over a dirty hose: Debris and contaminants in the hose end up in the hydraulic system. If you're unsure about crimping, bring your hose to us — we crimp using calibrated equipment and manufacturer-specified settings.