How to Measure a Hex Shaft and Bore

Posted on May 14, 2025 in FAQ, How To, Industry Formulas

Hex shafting and hex bore components are essential in industries like agriculture, robotics, and conveyor systems — and at MDS of Michigan, we make it easy to get the right fit. But before selecting the right hex shaft bearing, coupler, or collar, one thing matters most: accurate measurement.

Whether you are replacing a worn part or building a new assembly, here is our guide to confidently measure a hex shaft and bore. Click Here to download our guide or learn more below.

How to Measure a Hex Shaft

Hex shafts are characterized by their six-sided shape, but don’t let that fool you into thinking it is as simple as measuring flat-to-flat. For the most accurate result:

• Use a caliper (digital or dial preferred).
• Follow these steps:
  • Place one jaw of your caliper at a groove – not a flat – at the 6:00 position.
  • Place the other jaw at the opposite groove at either the 10:00 or 2:00 position.

Think of the hex as a clock face. Measuring from flat to flat can give you an incorrect size — so always measure groove to groove for the most precise measurement.

Tip: A standard 1″ hex shaft will not measure exactly 1″ across the flats — using the groove-to-groove method ensures proper component selection.

How to Measure a Hex Bore

Just like the shaft, a hex bore must be measured using the same groove-to-groove method. This ensures your shafting fits snugly into your bearing, coupler yoke, or other mating component without slippage or stress.

• Use the same 6:00 to 10:00 or 6:00 to 2:00 measurement method.
• Do not measure flat to flat — this will result in undersized or oversized part selections.

Why It Matters

Choosing the correct component dimensions is crucial, as improper measurements can lead to premature wear, costly equipment downtime, and potential safety hazards. Our quick measuring guide empowers you to avoid these issues, enabling smarter and more informed purchasing decisions. Whether you are ready to explore our full selection of hex shafting, and accessories on our online store or prefer personalized guidance, MDS of Michigan is your trusted source for high-quality power transmission products, and the expert support you can depend on.