I'm having trouble identifying this type of screw: it has a small hexagonal hole inset 2-3mm inside the barrel. Will a small hex key suffice or do I need something more specific?

(The view from above) View from the side

(The view from the side) View from above

Apologies for the poor quality of my photos! For reference, this is on the camshaft of the motor of a Barnstead Vari-Mix Rocker.

  • Allen key doesn't fit? Nov 10, 2014 at 17:41
  • It's considerably smaller in diameter than the smallest Allen key that I have (1.5mm). I wasn't sure if the cut-out sections protruding from the "nodes" of the hexagon inset required some additional head.
    – adamgeber
    Nov 10, 2014 at 18:35

2 Answers 2


Just looks like a hex set screw. An appropriately sized hex key should work.

enter image description here

  • I agree that it's probably a small Allen key, but bear in mind that these come on both metric and Imperial sizes and the smaller they get the more critical the fit. Other alternatives are Torx which are usually (but not always) six lobe, but if it were old (1970s or older) something with Bristol splines (male or female) would also be a possibility. May 5, 2021 at 6:22

Of the four images the top one looks to show a torx (or similar - there are other designs). Torx are available in very small sizes and are widely used in laptop computers for example. A T1, the smallest is only 0.81mm across the points of the driver.


  • Hello, and welcome to Home Improvement. Thanks for the answer; keep 'em coming. And, you should probably take our tour so you'll know how best to contribute here. Jan 7, 2020 at 3:42

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.