Re: flexible couplings for PCB router - coupling

> Dave have you any photos or seen any that anybody actually made this
> style?
>
> I've played with a lot of flex couplings over the years, the rubber
> spider style (oldham) are the cheapest, but they always seem to wear
> out and develop a lot of backlash. They need the spiders replaced
> periodically.
>
> My favorite is the helical beam, but I have not seen anybody discuss
> actually making one of them. The helical beam appears to be cut with
> a saw cutter, like a threaded toolpath around the axis of the tube.
>
> Rino is starting to sell some molded couplings that have the same
> construction as your drawing:
>
> http://www.rinomechanical.com/shftcoup_molded.htm
>
> They don't publish prices, so they may want too much to make them a
> viable alternative.
>
> Also here is an article about couplings(with definitions) that may be
> of interest:
>
> http://tinyurl.com/mgcce
>
> Fred Smith - IMService
> http://www.cadcamcadcam.com/hobby
>

I have not needed to make any as I have been very lucky to be able to
use rigid on everything so far.

I would make one if the need arose, but only to save the $5.00 the
Oldham costs from McMaster Carr.

5/8" OD, 13/16" long 1/8" to 3/8" shaft
6408K9 $2.28 ea

times 2, plus the spider.

BUT... the torque on the spider is really low.

The Rino ones are plastic and also have very low torque ratings.

As for the helical beam, you do need to run the cutter around and
'thread' the cut. They are super flexible. the one beam style (you
slit all the way past the bore and well into the opposite side, then
rotate the part 180°, move down and repeat so the connection is on
opposite sides) are also very flexible and would be MUCH easier to
make than a helical. Flexibility becomes a function of number of cuts
and thickness of the web.

The dual beam I described offers less flexibility as the span of the
flexing section is so much shorter.

Dave