CIM motor shaft Coupler

[Epot86]

Does anyone know of where to get a coupler for the small CIM motor shaft? We need something so we can connect the small output shaft (i think its like maybe 1/4) to a larger 5/8 in shaft to drive our ball launching wheels. We have something from a few years ago but its a three piece system and we were hoping to use just one piece. Thanks

[Andrew Blair]

It's a 5/16" output shaft. You can buy combination couplers, or you could just machine a 5/16" hole on one side of a piece of stock, and a 5/8" hole on the other. Or 5/8 ouput shaft.

EDIT----------------------------------------------------------------
Its an 8mm shaft. I was close...

[Manoel]

Originally Posted by Andrew Blair

It's a 5/16" output shaft. You can buy combination couplers, or you could just machine a 5/16" hole on one side of a piece of stock, and a 5/8" hole on the other. Or 5/8 ouput shaft.

Actually, it's an 8 mm shaft. 5/16" is 7.9375 mm. Good luck with the interference fit!

[Andrew Blair]

Originally Posted by Manoel

Actually, it's an 8 mm shaft. 5/16" is 7.9375 mm. Good luck with the interference fit!

Whoops, we use english, I always thought I was just getting a bad measure.

[Epot86]

so no one knows of a 8mm to 5/8 coupler existing. Also, where could a get the combination couplers that were mentioned above.

[Manoel]

Originally Posted by Epot86

so no one knows of a 8mm to 5/8 coupler existing. Also, where could a get the combination couplers that were mentioned above.

Machining one is entirely out of question?

[Kam-AL]

Instead of having a direct connection why not make a mini gear box in which a gear from the small shaft attaches to a gear in the large shaft. I think it might work, havent tried it myself.

[Andrew Blair]

http://www1.mscdirect.com/CGI/N2DRVSH

Unfortunately, I can't find a combo coupling, so you'll have to turn down the shaft you want to connect to 5/16" as well. You will have no trouble connecting 5/16" and 8mm, it's very close. Unless you really want it to be perfect.

[Ceal Craig]

You could use the old 1" Al hex block, drill appropriate size holes on either side, broach for key stock.

That is what we did on one robot recently

Ceal Craig

[Epot86]

first, how do u "broach for key stock" all we have is a drill press no other fancier tools. Also, how do u ensure that the holes are perfectly centered. If they are not wont it wobble and all break apart.

[Ceal Craig]

Well, that is a toughie with only a drill press, I admit. We cut the accurately holes using a lathe and have an arbor press and the tools to broach for the broaching.

Our first year (this is our fourth) we made one tool investment that has really paid off, we bought a bench top arbor press, for $200? or thereabouts. We broach key stock cuts in couplings, gears, sprockets, etc. and we press bearings in effectively and such. The lathe is a very old one we inherited when the auto shop closed at the school.

Sorry we couldn't be of more help. Best wishes!
Ceal Craig

[DonRotolo]

Originally Posted by Epot86

first, how do u "broach for key stock" all we have is a drill press no other fancier tools. Also, how do u ensure that the holes are perfectly centered. If they are not wont it wobble and all break apart.

It can be done with care. It might take an hour or two and four tries...
Broaching by hand is also possible, but I'd recommend against it. If you must, use a small file, and you can't hold it by hand - clamp it and make a sliding block.

Alternative: Make a flexible coupling. You can buy one, one side 5/16" and drill it out, the other side 5/8. Make one by drilling out two seperate pieces, and use a heavy piece of stiff rubber hose to connect the two sides together (use hose clamps, balance the assembly).

Don

[Theory6RobotiX]

You could drill a 5/16 hole in the end of a 5/8 peice of bar stock(hard with only a drill press, but i think it can be done ). And then you could drill and tap for a set screw on the face of the shaft to hold the output shaft from the CIM motor.
Hope this helps. Good Luck

[Biff]

The shaft is really 8 mm we just used a 5/8" by 1" piece of keyed shaft and drilled a 8 mm hole in the center with a drill press. Starting with a 1/8" bit held near the tip vertically with the shaft in the drill press. With care it's not too hard to center. We set the speed all the way up for this, Then reduced to normal speeds to drill the final 8 mm hole through. Then tapped for the second set screw on the sprocket, drilled in place and tapped so the treads between the sprocket and shaft with the 8 mm hole line up. Put a small dimple in the cim shaft add key (before you tap) to help with balance. One or our mentors has a 8 mm bit. You can get metric drill bits on-line or from a good tool supply, most hardware and home building places don't carry metric. As mentioned above a broach and a arbor press can be a big help, But there are other ways to get what you need.