Home made shaft couplers

[EL34]

I was looking at the silly prices they get for one nice motor shaft coupler. They were $15 each and up.

I saw these cool split clamps at Mcmaster-Carr but they were only 5/16" wide and only had one set screw.
I bought a few aluminum ones to try and see if I could join two of them to make a motor coupler.
They also come in a couple types of steel.

I clamped two couplers to a .25" shaft and then drilled 2 x 3/32" holes into the couplers.
I had some hardened 3/32 steel pins that I got somewhere years ago and so I epoxied them into the holes I drilled.

We will see how they work when I get my acme screws. Got to get good alignment of the motor and screws since they are rigid clamps.



My "work in progress" cnc project page
http://www.el34world.com/Misc/Cnc/CNC0.htm

[EL34]

Just an update on how these couplers are working after using them for a couple months.

No problems at all yet, they are holding up nicely.
The steel pins must be very tough.
Had one steel pin slowly work it's way out. I just applied some epoxy to the pin shaft and pressed it back in, and it has been fine since then.

My motor alignment is dead on the money so these couplers may not be good for a bad alignment or for high speeds.
I am using fairly slow turn rates on my motors and screws.

Anywho, these worked out to be cheap but nice coupling solution.

[One of Many]

I have taken the same approach with keyed set screw collars, only I used 4 neoprene pins that press fit into both collars. I also left a 3/16" gap between the collars to give a little shock cushion on direction reversal and absorb any mis-alignment issues. My particular application was rapid traversing a larger font printer head, so there isn't much load on the coupler anyways. The 2 printer rails I designed are now 2+ years running 2 shifts 5-6days/week at around 600-800 cycles/shift.

I had thought of taking the double thick collars and milling into them similar to a lovejoy and filling the voids with silicon or urethane to simulate the spider. By the time I did that, I may as well have bought the real McCoy.

The biggest problem with a rigid coupling is putting the bearings on either shaft at risk.

DC

[stirling]

LOL - you guys crease me - if I could get couplers for $15 (£7.50) in the UK I'd buy them so fast it would make your head spin.

[EL34]

You've been creased!

I guess, $45 for 3, if that's what they go for compared to less than $8

The money isn't an issue, but at the time I was building from scratch, I wasn't sure what the heck I needed, so I made them figuring I wasn't out much if they didn't work.

Plus it was fun and edjucational to make my own.

I may may get some of the lovejoy types eventually.

[One of Many]

Mine were 10-12mm shafts. The cheapest I had found at the time were in the $50-70usd range. By the time shipping and delays were added in, I decided to just get it done with what I had on hand. 15 minutes and the coupler was drilled and installed, since I already had the 1/4" neoprene pins for other purposes.

DC

[stirling]

I'm not knocking it guys - you're ingenuity is what it's all about - I just get dead jealous when I see US prices. I recently shipped a whole boxful of steppers from the States cos even with shipping, tax and import duty they worked out cheaper than getting them here.

[EL34]

I ship worldwide in my business.

Here's a shipping tip if you can get the states business to do it for you.

There is a flat rate Priority mail box that is only $37 for anything you can fit inside up to 20 pounds of weight.

You can fit a 13inch long piece of circuit board on the diagnal, but the box is 12 inches wide by about 8 inches high and 8 inches wide.

Stepper motors are very heavy but small so you could get a boatload of them in the flat rate box.
If you had three of them in a regular box it might cost you $50+ to ship.

I use that container alot when shipping tp my International customers.
Of course if you are getting parts longer than about 13", or more than 20 pounds, then the shipper cannot use the flat rate box.

[stirling]

Thank for the tip - I'll give it a try with my next order.