Model Forum / General / Models / April 2009

Oldham couplings are not expensive, look in Arc new catalogue and you
can get both halves and the torque disk for under a tenner.
I have to make certain specials and believe me if  could buy them for
the amount of work involved I would.

Oldham couplings do compensate for misalignment and because they are
separate it's not a continuous twisting action like the spiral cut
type.
If there is any large misalignment these will destroy themselves over
a period of time.

John S.

    --This latter type is called a helical coupling; invented in WWII
for use in bombsights, IIRC. The process for making them was kept a trade
secret for over 50 years. They're very neat couplings because they have
*zero* backlash, so they're very useful in things like cnc machines. The
biggest company making them is Helical Products. There's one other, newer
company as well but the name escapes me at the moment. If ya ever see 'em
surplus grab 'em; they last forever..

I have used Oldham couplings for my various projects and have found
them to work well and reliably. Both types are "zero" backlash -
although in reality, there is no such thing - the sliding plate in the
Oldham couplings will have some degree of give in it, and the spiral
type couplings are effectively coupling the two shafts together with a
spring that can wind up/unwind to some extent. So both types will
exhibit some backlash, depending on the load and the size of the
coupling.

Regards,
Tony