How to Crimp Hydraulic Hose: Step-by-Step Guide
Hydraulic hose crimping uses a hydraulic crimping machine to compress a metal ferrule onto the hose to a precisely specified diameter, permanently attaching the end fitting. The crimp diameter must match the manufacturer specification exactly. Always proof test at 2× working pressureafter crimping before placing in service.
What Is Hydraulic Hose Crimping?
Hydraulic hose crimping is the process of mechanically attaching end fittings to hydraulic hose by radially compressing a metal ferrule or fitting shell onto the hose body using a hydraulic crimping machine. The machine forces a set of segmented dies inward simultaneously, compressing the fitting to a precise, specified diameter that locks it permanently onto the hose.
The crimp connection is the industry standard for hydraulic hose assemblies because it provides a leak-free, high-strength, permanent connection that is rated to the full working pressure of the hose. Unlike threaded or push-on connections, a properly crimped fitting cannot loosen under pressure cycling, vibration, or temperature change.
Tools and Equipment Required
Hydraulic Crimping Machine
The core tool. Crimping machines range from bench-top shop units to portable field crimpers. They consist of a hydraulic cylinder that drives a die head, compressing the dies around the fitting to a dial-set or electronically controlled diameter. The machine must be capable of the required crimp force and compatible with the die set for the hose and fitting combination being assembled.
Die Sets
Each hose-fitting combination requires a specific die set. Die sets are sized to match the fitting shell outside diameter and are selected by fitting type and size. Using the wrong die set produces an incorrect crimp diameter and will result in assembly failure. Die sets must be kept clean, undamaged, and free of burrs.
Hose Cutting Equipment
Clean, square cuts are essential. A dedicated hose cutting machine or a sharp, purpose-made hose cutting blade produces a perpendicular cut without deforming the hose end. Utility knives, angle grinders, and saws are not acceptable for hydraulic hose cutting — they leave ragged ends that prevent proper fitting insertion and seating.
Crimp Diameter Gauge
A calibrated crimp diameter gauge (OD measuring gauge or vernier caliper) is used to verify the finished crimp diameter matches the specification. This is a mandatory quality check — not optional.
Insertion Depth Marking Tool
A marker or paint pen to mark the insertion depth on the hose before fitting insertion, confirming the fitting is fully seated before crimping.
Danfoss Crimping Equipment — What ARG Uses
All hose assemblies built at ARG Industrial branch locations are made using Danfoss crimping equipment. Danfoss (Aeroquip® by Danfoss) is the industry standard for hydraulic hose crimping machines, offering a full lineup from portable field units to full shop presses. Every Danfoss machine is engineered to precise tolerances and pairs with Danfoss crimp specification data, reducing operator error and ensuring consistent, rated assemblies every time.
The following Danfoss crimp machines are stocked and available through ARG Industrial:
| Machine | Type | Hose Capacity | Shop on ARG.com |
|---|---|---|---|
| ET500 | Portable field crimper — 29 lb, bench-mountable | Braided -4 to -12 | Spiral -6 to -10 | Shop ET500 → |
| ET1187 | Portable variable crimper — 10 ton, rectangular frame | Braided -4 to -16 | Spiral -6 to -16 | Shop ET1187 → |
| ET4020 | Benchtop crimper with dies included | Braided -4 to -20 | Spiral -6 to -20 | Shop ET4020 → |
| T-420 Coll-O-Crimp Super I | Shop press crimper | Braided -4 to -20 | Spiral -6 to -20 | Shop T-420 → |
| T-460 Col-O-Crimp | Portable shop/field crimper | Fiber braid 3/16 in to 1-3/8 in | 1-1/4 in 2-wire hose | Shop T-460 → |
All machines are Aeroquip® by Danfoss brand, stocked through ARG Industrial. View all crimping machines on teamarg.com →
Danfoss Crimp Specifications
Danfoss publishes crimp specifications for all Aeroquip and Danfoss hose-fitting combinations through their online Danfoss Crimp Specs tool. The tool lets you look up the correct crimp diameter and die set for any specific hose-fitting combination — eliminating guesswork and reducing the risk of assembly errors.
Step-by-Step Crimping Process
If a crimp is out of specification or a fitting leaks during pressure testing, the fitting must be cut off and the hose remade with a new fitting. Never attempt to re-crimp a fitting that has already been crimped once. Re-crimping does not correct an under-crimp and will damage the hose inner tube and fitting, creating an assembly that appears serviceable but has reduced strength.
Crimp Specifications — Why They Are Critical
The crimp diameter specification is the single most critical number in hose assembly. It is determined by the hose manufacturer and fitting manufacturer together and accounts for the specific hose wall construction, rubber compound, reinforcement layers, and fitting shell dimensions of that exact product combination.
| Crimp Deviation | Effect on Assembly | Risk |
|---|---|---|
| Correct spec diameter | Fitting locks onto hose inner tube and reinforcement | None — assembly rated to full WP |
| Under-crimped (too large) | Insufficient grip on hose; fitting can pull off under pressure | Fitting blow-off — high-pressure fluid hazard |
| Over-crimped (too small) | Inner tube punctured or crushed; flow restriction | Internal leak, hose failure, reduced life |
| Wrong die set | Uneven compression, deformed ferrule | Assembly failure at unpredictable pressure |
Crimp specifications are published by hose and fitting manufacturers. Always use the published spec for the specific hose-fitting combination. Always use the published specification for the specific hose-fitting combination being assembled.
Fitting Types for Crimped Assemblies
The end connection thread type is specified independently of the hose size. Common end connection types used on crimped hydraulic hose assemblies include:
| Fitting Type | Thread Standard | Seal Method | Common Use |
|---|---|---|---|
| JIC (37° Flare) | SAE J514 | Metal-to-metal flare seat | Most common North American hydraulic fitting |
| ORFS (O-Ring Face Seal) | SAE J1453 | O-ring on flat face | High-pressure, leak-free connections |
| NPT / NPTF | ANSI B1.20.1 | Thread interference seal | General industrial, less preferred for hydraulics |
| BSP / BSPP | ISO 228 | Thread + bonded seal or O-ring | European and international equipment |
| BSPT | ISO 7 | Tapered thread interference | European equipment, older designs |
| Code 61 / 62 Flange | SAE J518 | O-ring flange face seal | Large bore, very high-pressure connections |
Thread type must match the port connection at each end of the circuit. See our hydraulic fittings catalogfor available end connection types.
Common Crimping Errors and How to Avoid Them
- Wrong crimp diameter:Using an estimated or remembered crimp diameter instead of looking it up. Always reference the published specification for the exact hose-fitting combination.
- Wrong die set:Using a die set from a different fitting series or size. Die sets are not interchangeable between fitting types even at the same nominal size.
- Incomplete fitting insertion:Fitting not fully seated before crimping. The hose end should be visible at the inspection hole. An under-inserted fitting produces a crimp that holds the ferrule but not the hose inner tube.
- Ragged hose cut:A non-square cut prevents the fitting from seating properly, creates a leak path, and can puncture the inner tube during insertion.
- Skipping skive on skive-type fittings:Some fitting designs require the hose outer cover to be removed (skived) before insertion. Skipping this step prevents the fitting from seating and will produce a crimp that pulls off under pressure.
- Mixing incompatible hose and fitting brands:Not all hose and fittings are compatible even at the same dash size. Use manufacturer-matched or verified-compatible combinations and always reference the crimp spec for that specific combination.
- Skipping the proof test:The pressure test is the final quality gate. It catches any error missed in the assembly process. Skipping it means putting an unverified assembly into service.
Field-Attachable vs. Crimped Fittings
Field-attachable fittings (also called reusable couplings or field-attachable couplings) are designed to be installed and removed by hand tools without a crimping machine. They are available for most standard hose types and are used for emergency or temporary repairs when a crimping machine is not available.
| Feature | Crimped Fitting | Field-Attachable Fitting |
|---|---|---|
| Installation tool | Hydraulic crimping machine | Hand tools only |
| Pressure rating | Full hose WP rating | Typically lower; verify product spec |
| Permanent? | Yes — fitting cannot be removed | No — can be removed and reused |
| Best use | All permanent service applications | Emergency repair, field service |
| Reliability | Highest — industry standard | Lower — thread-dependent seal |
| Recommended for permanent service? | Yes | No — replace with crimped assembly ASAP |
Field-attachable fittings are a useful emergency solution but should be replaced with a properly crimped assembly as soon as a crimping machine is accessible.
ARG Crimping & Assembly Services
Team ARG builds and pressure tests custom hydraulic hose assemblies across all branch locations. Our technicians use calibrated crimping equipment, manufacturer crimp specifications, and proof pressure testing to produce assemblies you can put into service with confidence. Whether you need a single emergency replacement or an ongoing supply of assemblies for your fleet or facility, we build to spec, test to spec, and stand behind the work.
We also operate the ARG Crimper Lease Program— placing Danfoss crimping equipment at customer locations for in-house assembly capability with ARG-supplied hose and fittings. Ask about the ET500 portable Danfoss crimper for field service operations and the FT1390 for full-range shop capability. Contact your nearest branch to discuss whether a crimper lease makes sense for your operation.
Frequently Asked Questions
Hydraulic hose crimping is the process of mechanically attaching end fittings to hydraulic hose by compressing a metal ferrule onto the hose to a precisely specified diameter using a hydraulic crimping machine. It creates a permanent, pressure-rated connection that is the industry standard for hydraulic hose assemblies.
The correct crimp diameter is specified by the hose and fitting manufacturer in their crimp specification chart for the specific hose-fitting combination. Never estimate crimp diameter. An under-crimp causes the fitting to pull off under pressure; an over-crimp damages the hose inner tube. Always look up the published spec.
No. Hydraulic hose crimping requires a hydraulic crimping machine. For emergency field repairs without a crimper available, field-attachable fittings can be used temporarily, but they should be replaced with a properly crimped assembly as soon as possible. They are not rated for permanent high-pressure service.
A crimped fitting is permanently attached by machine to the full working pressure rating of the hose. A field-attachable fitting uses a threaded or mechanical connection installed by hand tools, is typically rated lower than the hose, and is intended for emergency or temporary repairs. Always replace field-attachable fittings with crimped assemblies for permanent service.
Measure the crimped diameter with a calibrated gauge and verify it matches the manufacturer specification. The hose end should be visible at the fitting inspection hole confirming full insertion. The ferrule should be uniformly compressed with no cracks or splits. Confirm with a proof pressure test at 2× working pressure before putting the assembly in service.
A properly crimped assembly used within its rated pressure and temperature range typically lasts 1 to 2 years in high-cycle mobile equipment service and longer in lower-cycle industrial applications. Actual service life depends on operating pressure, temperature, routing, bend radius, fluid compatibility, and environmental conditions.
Yes. Team ARG builds, crimps, and proof tests hydraulic hose assemblies at all branch locations. Bring in a sample of your failed assembly or your specifications and we will build a replacement to spec. We also offer the ARG Crimper Lease Programfor customers who want in-house crimping capability.