I was browsing this website and noticed that they have drilled washers.

enter image description here

I could start to guess that the purpose of drilled washers may involve reducing weight by removing material (although this would compromise its structural integrity and ability to do its job as a washer of distributing a bolt’s load) or maybe the holes allow for greater grip/frictional force somehow.

Maybe it is used when a huge bolt is to be surrounded by a circle of bolts that would fasten the washer. But at this point, it does not seem reasonable to call it a washer anymore?

  • 2
    $\begingroup$ I've seen similar items designed to increase mechanical engagement when held on by adhesive $\endgroup$ Commented Sep 12, 2021 at 11:21
  • 1
    $\begingroup$ Looking at a few websites, their main function seems to be to look pretty in applications which are not very critical and easily visible. Motor bike customization seems a popular use for them. Compared with everything else, the weight saving is negligible. $\endgroup$
    – alephzero
    Commented Sep 12, 2021 at 13:09
  • $\begingroup$ Re my first comment: catalog.pemnet.com/viewitems/varimount--base-plates/… $\endgroup$ Commented Sep 12, 2021 at 14:07
  • $\begingroup$ Yes, re: J Swift's comment, I've seen flanges with this kind of shape, in studs and hardpoints meant to be embedded in fiberglass/epoxy structure.. Alshough some of them, like the third one, don't look like it because the holes are too small. Could it just be a combination washer for a bolt pattern, to reduce part count? $\endgroup$
    – Pete W
    Commented Sep 12, 2021 at 15:21
  • $\begingroup$ FWIW, upon closer inspection, the diagram that is labeled M6 has the ring of holes in positions that are not even placed symmetrically (unlike the other illustrations), so to me it does call into question the relative sizing of the holes for that one too. $\endgroup$
    – Steven Lu
    Commented Sep 12, 2021 at 23:41

1 Answer 1


Depending on the size and thickness these could be spacers. One example is their use on cars to increase the track.

They can also be designed as flexible drive plates between a motor and gearbox for example, with alternate bolts for the motor.

Some are also designed as seals or separation plates between things like pipe flanges.


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.