Crimping in Style - Molex MicroFit 3.0 Hand Crimp Tool Review

Table of contents

RoadTest: Cool Tools - Molex Hand Crimper

Author: dougw

Creation date:

Evaluation Type: Connectors & Cable

Did you receive all parts the manufacturer stated would be included in the package?: True

What other parts do you consider comparable to this product?: Molex makes many other crimpers of similar quality to this crimper, but they are designed for different connectors.

What were the biggest problems encountered?: I had some supply chain problems getting connector components to test with this crimper - just slow delivery, which delayed the road test.

Detailed Review:


Making electrical connections to wire is a major requirement throughout the industry and crimped connections have proven to be an excellent way to accomplish this task, especially when the joint needs to have a combination of strength, durability and electrical continuity.

To achieve an optimal crimp requires precision tooling combined with appropriate connectors, wire sizes and insulation diameter.

Unfortunately there are a very wide variety of connectors and wire that could be crimped, so a single tool can only handle a small subset of possible connections. Molex alone makes approximately 570 hand crimping tools, and of course they also make more automated crimping tools. In an industrial application good crimping tools are a worthwhile investment but for hobby operations, buying a bunch of good crimping tools gets very expensive.

I was keen to apply for this road test because the tooling on offer was high end and covered a useful range of connectors


Molex History

Molex was started in Illinois by Frederick A. Krehbiel who invented a plastic called Molex around 1938.

Today Molex manufactures over 100,000 products.

2/3 of Molex business is now outside the USA and the crimper being reviewed here lists Sweden as it country of origin.

I have been using Molex connectors since before the IBM PC was developed and of course the ubiquitous PC has multiple Molex connectors in it - connecting power supplies to the motherboard and peripherals.

Although there are vast numbers of connectors and connector companies, it seems Molex ends up being the goto connector for many applications.

Crimp Technology

Crimp technology seems to have been developed around 1953 by AMP to terminate stranded wire in a more robust terminal.

Since then crimped connections have become staples of the industry, in both senses.

An ideal crimp creates a strong, cold-formed gas-tight, low impedance connection. Connectors in general facilitate connecting wires to anything, including other wires, and crimp technology also makes applying connectors quick and robust, even lending itself well to automation.

Crimp Objectives and Characteristics

The objective of an electrical crimp are to compress the connector and wire enough to exclude air and cold weld the metals together without compressing so much that the wire gets sheared. If cold welding is not achieved, the connector may relax and spring back, resulting in a poor electrical and mechanical connection. Cold welding deformation results in work-hardening of the metal which makes it more brittle and more susceptible to metal fatigue cracks, so it is important that the connector shank, that extends to the insulation crimp, provide more resistance to bending than the insulated wire. This geometry greatly reduces bending stress at the cold welded joint. The insulation crimp provides a flexible transition that distributes bending stress over a longer distance, which in turn greatly reduces bending stress at the transition to unsupported wire.

Solder joints do not induce work-hardened brittle areas, but solder that wicks into stranded wire constrains it so it cannot bend, which creates a high bending stress where the wicking ends, leading to one of the most common failures in wires and cables. Also, solder is a very weak metal that is prone to stress fracture from vibration and bending. In addition solder has a different coefficient of thermal expansion than copper, so thermal cycling will cause stress and fatigue in the joint.

Both types of joint can be done poorly, a cold solder joint in one case and incorrect crimp force in the other but a good crimp is usually at least as good as a good solder joint in most applications, and it is often easier to automate or execute quicker.

Unboxing & Device Description

The unboxing video describes crimper features, crimper operation, crimper adjustment and crimper maintenance. It also compares this crimper to another model.

This first video includes a discussion of crimp forces and the pin locator mechanism.

Test Plan

To provide a bit more rounded review, I ordered housings, headers and different pins and sockets in the MicroFit series, however only only one type of housing and only one header has arrived at this time and I really need to get this review posted so The review will focus on the parts I have.

Crimper Demonstration

A Raspberry Pi HQ Camera digital microscope was used to demonstrate crimping action, both hand-held and braced in a vise.

Visual Inspection

The second video includes visual inspection of completed crimps.

It also includes visual inspection of crimp cross section after they have been sliced with an abrasive cutter wheel and polished with fine grit sandpaper.

Dimensional Measurement

Dimensional measurement on completed crimps was also performed using digital calipers. This method can be used to non-destructively asses crimp performance and quality.

Strength Test

Pull force tests were performed to determine typical disconnect force as well as a destructive pull test to see how much force was required to break the wire.


The fairly crude test on 22 gage wire crimps exceeded the UL and DIN requirements and was right about equal to the NASA requirement for crimp strength.

Impedance Measurement

Impedance was measured using a four-wire method.

The impedance of the crimp is lower than the impedance of the wire, which means there is no impedance penalty for using these crimp connectors.

Conclusions & Discussion

What I liked:

The aesthetics and ergonomics of this Molex crimper are extremely good. The grips are comfortable and the squeeze force necessary to effect a high force crimp is much lower than non-premium crimpers.

The pin locator guide and linear jaw travel along with a precision mechanism combine to make consistently high quality crimps with fewer steps, so not only does this crimper make superior crimps it makes them faster than other crimpers.

The MicroFit line of connectors take the Molex connector concept to a new level of miniaturization, which is so important in modern electronics.

What I didn't like:

I loved the crimper, so these quibbles are more of a generic wish list than complaints specific to Molex. These premium crimpers do a great job but they are correspondingly expensive. They also have a limited number of connectors that they can crimp. These 2 issues taken together mean that it is prohibitively expensive to own a set of crimping tools that meets all needs.

Discussion of Applications for Crimping

I won't be able to afford a full set of premium crimp tools, so I will standardize as much as possible around the MicroFit line and get the most out of this great crimper. To this end, I have already ordered a selection of pins, sockets, housings and headers that I expect to use regularly in my projects. Most have not arrived yet or there would have been more examples and demos in the road test, but they will show up in future projects. Fortunately we were allowed to request the crimper we thought would be most useful when we applied for the road test, so this crimper will be maximally useful in my projects. (spoiler alert) One project that I expect to use these connectors on is a set of drum pads that will plug into a MIDI controller.

What I learned

I'm not sure why, but it surprised me that the crimp impedance was lower than an equivalent length of wire.

I was impressed at the cold welding achieved in the crimp joint. There is no air in there whatsoever.

I was also suitably impressed with the mechanics of the crimping mechanism and how it achieved high crimp forces with little manual effort.

I expected the crimper to make good crimps, but the ease of use features were outstanding.


I am very happy I was chosen to road test this crimper, it is going to find a lot of uses in my shop. I found this Molex crimper to be a very impressive tool. It does its job extremely well and appears very solidly built. I expect it will outlast me. Effusive thanks to Molex and element14 for sponsoring this road test. It is very satisfying to own and use a high quality tool like this.

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