Helical Couplings

grepper

grepper

Registered
Registered
Joined
Jan 8, 2016
Messages
171
So, the motors I ordered have an ~8 mm shaft.

http://us.stepperonline.com/3pcs-of...motor-35a-31nm439-ozin-24hs343504d-p-398.html

The CNCFusion site says the helicals they have will only work on 1/4" shaft - not exactly ~8 mm. Is that going to be a problem? If so, is it worth sending the motors back and getting different ones?

What about this? Way less than $25 from Fusion.
http://www.amazon.com/uxcell-5mmx8mm-Helical-Coupler-Coupling/dp/B00KHTVOEU
Shaft Usage : 5mm to 8mm / 0.2" to 0.31"(1/5" to 5/16");Length : 25mm / 0.98"

It seems to indicate motor shaft from 5 mm to 8 mm. How does that work? By carefully centering the shaft using the surrounding set screws?

Geeze. I can't seem to do anything with endless questions arising!
 
I hear the helical couplers tend to load up and cause backlash issues, apparently the flex disc type are better.

Others with more experiance with them may have better info.

Stuart
 
I have no experience using helical couplings so I can't comment on how well they will work with your setup. For reference on my PM-932 conversion I use double disk diaphragm style couplings and I can't detect any backlash associated with the couplings. Cost was about $21 each on eBay.

Tom S.
 
Mark:

You need to get couplings that have the correct bore(s) for the shafts being used - the one you linked to is 5mm on one end and 8mm on the other.
Couplings that are split through the hub and clamp onto the shaft are a better solution than those relying on setscrews. Like the type shown with the integral clamps here.

Personally - I've never had great success with beam (helical) couplings, but that was in applications that usually ran 16 to 24 hours a day. If you have three the same, I would recommend buying a spare.
 
Last edited:
An Oldham coupling is very good in this usage. Available from McMaster and others. The helical are available in the size you need. Ebay is a good place for them.
 
Thanks guys. Until today I had not thought of how to connect the motor. Really shows how unfamiliar I am with this stuff. After a bunch of searching around I see that there are all sorts of different types; premachined major & minor bores, some that can accept a range of motor shaft sizes, 5 mm to 8 mm for example, others that are called "zero backlash" but are split with different ID bore hubs available, etc. Of course there are many to choose from.

I'll check out the ones you have pointed to. Nothing like the voice of experience.

I don't know the length I need or the max OD that there is room for. I've emailed Fusion (they don't have a listed phone), but have yet to hear from them. Oddly, it appears that they only offer 1/4" motor shafts couplings. Strange.

Really appreciate the input. Thanks!
 
If nobody mentioned it, you want the split ones, not the ones that have set screws that impinge on the shaft.

The other option is to build your own zero lash couplings:grin: I designed and built couple for a quick disconnect system for a stepper system on a special machine.
 
Even though I hadn't given it any consideration, at first I thought there would be some sort of shaft, bored at each end and the motor would somehow just clamp to the screw. I mean, how difficult is that?

I was staring at pages and pages of various couplings and it suddenly (I can be dimwitted sometimes) dawned on me the reason for all the fuss; that these things are acting like an auto u-joint. Somewhere along the line I missed that step. I'm guessing that once all this kit stuff is bolted together that things probably don't align perfectly, and if there was not some flex between the motor and the screw that something, probably the motor, would get trashed fairly quickly. Duh.

Now it makes total sense why
Jim_Hbar said:
Personally - I've never had great success with beam (helical) couplings, but that was in applications that usually ran 16 to 24 hours a day. If you have three the same, I would recommend buying a spare.
Click to expand...

The helical stuff appears to flex because of slits cut into the side of the coupling allowing the metal to bend. That would seem to be doomed to failure from metal fatigue, or crud buildup in the cuts in the metal.

Obviously I don't know much about this, but I would think there would be a better solution. Or maybe for this application it would be just fine. I'm clueless. I'll check out the Oldham couplings that Dave suggested.

Backlash in the whole drive assembly would seem to me to be really something to be avoided as much as is reasonable.
 
You must log in or register to reply here.
Back
Top