Shaft Coupler - 1/4" to 5/16"

These stainless steel shaft couplers allow you to couple two size shafts together. They can be used for connecting motor shafts to drive shafts, or two different-sized shafts. These shaft couplers have a length of 0.75”, a outer diameter of 0.50”, and couple 1/4” to 5/16"shafts.

Actobotics is a robotics building system based around extruded aluminum channels, gears, precision shafts, and ball bearings. Thanks to the two standardized hole patterns, nearly all Actobotics components can be intuitively connected together. The wide range of components makes building complex electromechanical prototypes or finished projects a reality.

  • Length - 0.75”
  • Diameter - 0.50”
  • Bore A ID - 1/4”
  • Bore B ID - 5/16"

Shaft Coupler - 1/4" to 5/16" Product Help and Resources

Core Skill: Robotics

This skill concerns mechanical and robotics knowledge. You may need to know how mechanical parts interact, how motors work, or how to use motor drivers and controllers.

1 Robotics

Skill Level: Noob - You will be required to put together a robotics kit. Necessary parts are included and steps will be easy to follow. You also might encounter basic robotics components like bearings, mounts, or other hardware and need a general idea of how it goes together.
See all skill levels

Core Skill: DIY

Whether it's for assembling a kit, hacking an enclosure, or creating your own parts; the DIY skill is all about knowing how to use tools and the techniques associated with them.


Skill Level: Noob - Basic assembly is required. You may need to provide your own basic tools like a screwdriver, hammer or scissors. Power tools or custom parts are not required. Instructions will be included and easy to follow. Sewing may be required, but only with included patterns.
See all skill levels


Looking for answers to technical questions?

We welcome your comments and suggestions below. However, if you are looking for solutions to technical questions please see our Technical Assistance page.

Customer Reviews

2 out of 5

Based on 1 ratings:

Currently viewing all customer reviews.

Not quite fitting

I measured the shaft with my calipers (a nice pair of calipers btw), and it was 5/16". I measure the other shaft and it was 1/4". So I got this coupler to connect the two. The 1/4" connected just fine, but the 5/16" would not go on at all. I measured the inside of the coupler and it was 0.3010", which is a completely irregular size.(fyi 5/16" = 0.3125"). Is it possible that this was intended to be a Standard to Metric adapter? The hardware itself is excellent, the measurements and/or manufacturing tolerances are not.

Hi, I measured a Actobotics shaft and this coupler. Both fit together nicely. And they both measured in at 0.3125". If you would like to have us check out your coupler, please contact us at