Shaft couplings??

**Lanny** · 06-25-2003, 05:46 AM

Guys,

What kind of couplings did you use for the motor to the ballscrew?
I was going to use solid couplings I made out of brass but I heard somewhere that it was a no-no

I saw a dealer online that sells helical couplers, but at $27 a pop I know there has to be a cheaper solution. I thought about using vacuum hose that JK uses (on that other site

) , but I just don't like that route, want something a little more professional looking.
Any ideas?

Almost forgot, here's the machine I currently building.

Similar Threads:

**cncadmin** · 06-25-2003, 07:35 AM

helical couplers are the only way to go.

**sorincnc** · 06-25-2003, 02:45 PM

I second that. There is a fine line that sometimes you can't cross. I
Sorin

**HuFlungDung** · 06-25-2003, 03:15 PM

I don't see too much wrong with a solid coupling if the alignment is perfect. In a face mount situation, this is usually not too hard to accomplish, if the mounting surface has been machined perpendicular to the screw. In such a case, then the motor can be mounted on the screw, supported only by the coupling, and then the motor screws can be tightened.

If you cannot guarantee the perpendicularity of the face, then use the helical coupling.

For driving an encoder, I'd always use the helical coupling because of the possiblity of damaging the delicate instrument bearings in it.

**balsaman** · 06-25-2003, 05:16 PM

I used solid couplings for the motor to screw, helical for the screw to encoder. The screw is not supposrted at the motor end, other than by the coupling.

Eric

**Lanny** · 06-25-2003, 08:42 PM

Hmm, I don't know if I could machine the motor mounts accurately enough to go with the solid couplings. I mean if I could get my mounts to within .006" would that be enough?

Somehow I doubt it. I'll probably go ahead and layout the cash and get the helical couplings.

Forgot to mention, I'll be building a wooden cnc router first for making some of the components of the aluminum one. Almost have it finished and I've got most of the materials for the aluminum one already. How's that for ambitious

Electronics I know really well and I'm also a cabinet/furniture maker so most of what I'm doing isn't too far out for me, but machining metal is something I've never done. Wish me luck

Thanks to all for the help and I ALWAYS appreciate comments or crits. We all have to learn somehow.

**boxwood** · 06-25-2003, 09:12 PM

These are pretty good, It,s what I am using 3 piece design

http://www.mscdirect.com/PDF.process?pdf=3555

**sidi_steve** · 06-26-2003, 06:32 PM

If you can use 1/4 to 1/4 couplers, try http://www.meci.com and do a search for couplers. They have a 3 piece aluminum and rubber one there for a rather good price. I used 3 of these on my machine and they work pretty well.

Steve

**Lanny** · 06-27-2003, 12:29 AM

Steve,
Any problem with backlash on couplings from MECI? Being as frugal (cheap) as I am that would be perfect.

I also like the three piece couplers with the spider insert.
Thanks guys for all the help.

**anoel** · 06-27-2003, 12:26 PM

I bought a bunch of those and they work great.

**sidi_steve** · 06-27-2003, 12:33 PM

>Any problem with backlash on couplings from MECI?

As far as true backlash, there seems to be none. The picture on the website doesn't do the design justice. The rubber part of the shaft coupler is probably about a half inch long. Each aluminum collar extends nearly 1/4 each or so into the rubber sleeve. The part of the aluminum collar that extends into the sleeve has deep grooves that match deep grooves in the sleeve, so there is no slop.

I have not tried to measure if there is any 'twisting' of the rubber sleeve itself, but there appears to be virtually none.

Verdict: I think this coupler does a good job of directly translating the rotational forces of my 135oz/in steppers on to the rotating "leadscrew" -(in my case, 1/4-20 threaded rod)

Additional Note: At least one of the axes on my machine has less than perfect alignment between motor shaft and leadscrew. The coupler seems to do a good job of handling the mis-alignment.

Steve

**castguy2003** · 06-27-2003, 01:18 PM

No way .006 perpendicularity is going to be close enough for solid coupling. You need in the neighborhood of .0006.

Mike

**twombo** · 06-27-2003, 04:22 PM

Try McMaster-Carr P.N. 6208k14... it is a great solution at $27.58 ea. Can be configuree 3/8" in 5/8" out. All these others being suggested look more expensive and less capable.

Smaller ones are even less from MC. If ya haven't checked outhe MC online catalog, it's great.

Not nessarily the cheapest always ,but they always seem to have the part!!

**tsalaf** · 07-01-2003, 12:43 AM

I just ordered a set of these http://www.herbach.com/Merchant2/mer...t_Code=MEC-002

They are made of steel and appear to be more robust.

**mwestern** · 07-03-2003, 01:40 AM

I don't know if anyone else has tried this?

I am using universal socket joints (the kind you put on a ratchet) and I made solid couplers (clamping type) to fit on each side of the uni-joint. My motor mounts are 3/8" and the uni-joints are 1/2'' Dia. So I made two solid couplers. The first one is 3/8" on one side and 1/2" on the other side to accomodate the uni-joint. The second coupling is 1/2" on both sides. This accomodates the uni-joint on one side and the lead-screw on the other.

The uni-joint cost me $4.00 and I made the couplers out of scrap round stock in my shop.

I can post some pics if any one is intereasted.

Mark

**abasir** · 07-03-2003, 01:51 AM

I'll be interested to see the pics of the setup as I'm still searching for low cost ideas for couplings. I'm still using solid coupling for my setup.

**cbcnc** · 07-03-2003, 02:20 AM

I saw a picture somewhere, though I don't remember where, of a coupling like a solid one but he had made several saw cuts part way thru in different places. Seems kind of crude now that I think about it. Maybe to the point of getting hard and soft spots as it is rotated.

Chris

**balsaman** · 07-03-2003, 09:29 AM

An interesting solution. Pics would be great.

I am backing off my solid couplings. Going to get some other couplings today. Even when acurately made, the setscrews induce some wobble/missalignment.

Eric