Thread pitch comes up a lot in linear actuator conversations, usually without much explanation. Engineers see it on datasheets, designers reference it when comparing products, and most people roll with it without being entirely sure what it actually means or why it matters.
This article clears that up. We will cover what thread pitch is, how it works in the context of a lead screw, and why Actuonix actuators use a multi-start thread design.
What Is Thread Pitch?
Thread pitch is the distance between two adjacent thread crests, measured along the axis of the screw. On metric screws it is expressed in millimetres. A screw with a 1mm pitch has threads sitting 1mm apart along its length. A screw with a 3mm pitch has them 3mm apart.
That distance controls one fundamental thing: how far the nut travels along the screw per revolution.
Related Article: How Lead Screws Work in Micro Linear Actuators
Single-Start vs Multi-Start Threads: What Is the Difference?
A single-start screw has one continuous helical groove running along its length. One full rotation of the screw moves the nut a distance equal to the pitch. That is straightforward.
A multi-start thread is different. Instead of one groove, there are two or more grooves running in parallel along the screw. Each one is a separate thread start. The nut engages all of them simultaneously as it travels.
Here is where it gets interesting. On a two-start screw, one full rotation moves the nut the distance of two pitches, not one. On a three-start screw, one rotation covers three pitches. The pitch of each individual thread stays the same, but the nut travels further per revolution because it is engaging multiple threads at once.
Why Actuonix Actuators Use a Multi-Start Thread Design
All Actuonix actuators use a multi-start lead screw thread. This is a deliberate design choice, and understanding why helps explain some of the performance characteristics you will notice when working with these products.
The main reason comes down to the relationship between thread engagement and efficiency. A multi-start thread distributes the load across more contact surfaces simultaneously. For a compact micro actuator where the screw diameter is small, this improves how smoothly the nut tracks along the screw and reduces the chance of uneven wear over time.
There is also a practical benefit in how the design handles the balance between speed and load capacity at the micro scale. By using multiple starts, Actuonix can maintain a finer individual thread pitch for load bearing purposes while still achieving a usable lead for movement.
The thread pitch varies across the Actuonix product family. The PQ12, L8 and L12 share the same motor and gearbox but use different lead screw diameters and lead/pitch values. This is why these models produce different speed and force outputs even though the drive system behind them is the same.
What the Datasheet Numbers Tell You About Thread Pitch
You will not find thread pitch listed directly on Actuonix datasheets. What you will find is the output of it: no-load speed and force figures for each gear ratio variant.
Take the L12 as an example. The 50:1 variant runs at 25mm/s with no load and produces a maximum force of 22N. The 210:1 variant runs at 6.5mm/s and produces up to 80N.
The L16 tells a similar story. The 35:1 variant tops out at 32mm/s with a maximum force of 50N. Move to the 150:1 variant and that becomes 8mm/s and 200N.
View all Actuonix datasheets here: Product Datasheets and 3D Files
Thread Pitch and Mechanical Backlash
Backlash is the small amount of play between the screw and nut when the direction of movement reverses. It shows up as a tiny dead zone where the motor starts turning but the rod has not yet moved.
The L12 datasheet lists mechanical backlash at 0.2mm. The L16 lists 0.25mm. For most applications these figures are perfectly acceptable.
Frequently Asked Questions
Is thread pitch listed on Actuonix datasheets?
Thread pitch is not listed directly on Actuonix datasheets. The performance output of the thread pitch design is reflected in the speed and force figures for each gear ratio variant.
Does thread pitch affect backlash?
Yes. Thread pitch is one of the factors that influences how much play exists between the screw and nut when movement direction reverses.
Find the Right Actuator for Your Project
Actuonix micro linear actuators are available across multiple gear ratio options in the L12, L16, P16 and other product families. Use the Actuonix Actuator Selector Tool to filter by force, stroke and control type, or contact our team for OEM and custom requirements.
