M-SERIES CONNECTORS COMPARED: WHEN TO CHOOSE M8, M12, M17, OR M23

What is the difference between M8, M12, M17, and M23 connectors? M8, M12, M17, and M23 refer to the thread size in millimetres of a circular industrial connector. The usable current, voltage, contact count, coding, and Ethernet capability depend on the specific insert and connector design, and are not fixed family truths. As a rule of thumb, M8 is typically used for compact sensor connections, M12 for general automation I-O and selected industrial Ethernet applications, M17 for compact servo and feedback applications, and M23 for higher-contact or higher-power motion-control connections. Validate the actual current, contact, and Ethernet limits against the EPIC® Circular Connectors Guide and the per-SKU datasheet.

For mechatronics designers, automation engineers, and senior electrical engineers selecting connector standards across ASEAN, LAPP designs and manufactures cables AND connectors as part of one engineering programme. The EPIC® range spans M8 through M58 in SIGNAL and POWER variants, and LAPP SEA holds regional stock for the sizes most commonly specified for industrial automation, packaging machinery, robotics, and intralogistics builds. The Mar W1 companion piece on EPIC® industrial connectors covers the broader EPIC® range and how it compares to other connector brands. This article focuses on size selection within the M-series.

What Is the Difference Between M8, M12, M17, and M23 Connectors?

The M-number in M8, M12, M17, and M23 is the thread diameter of the coupling in millimetres. The other variables, current rating, contact count, insert configuration, IP target, Ethernet capability, mating-cycle envelope, depend on the specific part, not on the M-number itself.

M8 housings are sized for low pin counts at compact sensor loads. They are the smallest of the four most-specified circular sizes, and they go into I-O block connections, sensor leads, and short-run feedback applications where panel real estate is at a premium.

M12 is one of the most widely specified circular connectors in industrial automation. It covers general sensor and actuator I-O, selected industrial Ethernet duty in shielded variants, and the bulk of the field-side connection between PLCs and the rack. M12 hits a size and current trade-off that keeps it broadly deployable.

M17 sits between M12 and M23. It is used where M12 runs out of pin count or current envelope but M23 is more housing than the panel layout needs. Compact servo and feedback applications often land in this range.

M23 is the workhorse for motion control and higher-current applications. SIGNAL and POWER variants cover the bulk of servo motor and drive connections, with insert density that M17 and below cannot match.

Sizes above M23, such as M40 and M58, exist in the EPIC® range for higher-power and specialty applications but are less commonly specified in standard industrial automation panels. They sit outside the typical M8 to M23 selection question that drives most machine-builder decisions.

How Do You Choose the Right M-Series Size for a Servo or Sensor?

The selection question reduces to three engineering questions and a fourth standardisation question, asked in order.

What current and voltage need to flow through the connector at peak load? Power-side decisions usually push toward M23 because the larger housing accommodates higher-current contacts. Sensor-only and signal-only connections rarely need anything past M12.

How many contacts are required, and what coding? Higher pin counts push toward larger housings. Coded variants on M12 (A, B, D, and X coding) reduce field misconnection risk and matter when multiple connector types share a panel.

What is the worst environmental exposure the connector will see? IP target and mating-cycle expectation are driven by the application, not by the size. The M-number determines the housing envelope, not the IP rating.

And the fourth question, standardisation. If most of the machine runs on one size, is it worth standardising the few outliers to match? The standardisation answer trades panel optimisation for inventory simplicity.

For each of these questions, the EPIC® Industrial Connectors APAC overview sets out the SIGNAL and POWER variants per size.

M-Series at a Glance: Comparison Reference

The table below covers the size definition and the rule-of-thumb application per M-size. Specific current, voltage, contact count, panel cut-out, and IP rating are confirmed on the per-SKU datasheet, not estimated against a size column. The reason this article does not publish a single rating number per row is that within one M-size the envelope changes with the insert and the housing variant. A single ‘M12 amperage figure’ would be wrong for half the use cases it describes.

Size	Thread Diameter	Typical Application (rule of thumb)	Detailed Spec
M8	8 mm	Compact sensor connections, sensor leads, short-run feedback	EPIC® datasheet
M12	12 mm	General automation I-O and selected industrial Ethernet	EPIC® datasheet
M17	17 mm	Compact servo and feedback	EPIC® datasheet
M23	23 mm	Higher-contact or higher-power motion control	EPIC® datasheet

These are not fixed family truths. They depend on the specific insert and connector design. The EPIC® range catalogue is the source of record for SKU-level data.

When Should You Standardise on One M-Series Size Across a Machine?

Standardisation cuts spare-parts inventory and field-service complexity. It costs panel real estate when an oversized connector goes into a slot that could have taken a smaller size. The trade-off depends on the machine.

For high-mix, high-changeover packaging machines and intralogistics platforms, the spare-parts and service savings usually outweigh the panel-real-estate cost. One connector size across the machine, with the right insert mix for each role, is the practical default.

For dense automation panels with a fixed bill of materials, mixing M8 sensor connections with M12 I-O and M23 servo connections is the more efficient layout. The spare-parts cost is real, but the panel-density gain is also real.

The actual call depends on production volume, changeover frequency, and how the spares budget is structured. LAPP SEA can scope SKU options per size against an actual machine bill of materials.

Talk to Our Engineers

If you are standardising a connector range across a new machine platform or refreshing an existing range, talk to our engineers. We can scope EPIC® SIGNAL and POWER variants at each size and confirm regional stock through LAPP SEA across Singapore, Malaysia, Thailand, Vietnam, Indonesia, and the Philippines. We can also pair the connector with the matched ÖLFLEX® or ETHERLINE® cable.

Reach the LAPP APAC team at e.lapp.com/apac/contact, or browse the EPIC® M-series options in the LAPP SEA eShop to start scoping by size.