Can I put a sprocket made for a keyed shaft on a D bore?

[Naio]

This is for my shave ice machine.

I overheated my motor and need to send it to a shop for rebuilding. I have available a possible temporary replacement motor. But my main motor has a keyed shaft, and the replacement has a D shaped shaft.

I talked to the people at the local sprocket shop where I am, and they said they thought I could use my keyed sprocket on the D shaped shaft. They suggested just tightening the set screw real well on the flat part of the D, and maybe even using a drill to make a dimple there.

The machine requires quite a bit of power and torque. When I used a 100 amp fuse I sometimes blew it. I now have a 200 amp circuit breaker which I have never blown.

I guess the worst case scenario is that the set screw would score the shaft of the temporary motor? Could anything else go wrong?

The drive sprocket is small and off the shelf. But the larger sprocket that the chain turns is new, aluminum, custom-made, and there's no way I'm ever going to get another one. Would I be endangering it in any way?

Here are some pictures, not of my equipment specifically, but of a sprocket that goes on a keyed shaft, and a one that goes on a D-shaped shaft, in case people are wondering what the heck I am talking about 🙂

https://www.amazon.com/Yerf-Dog-Jackshaft-Sprocket-Tooth/dp/B01MSYOY2G

http://tncscooters.com/index.php?route=product/product&product_id=461

[Naio]

Thank you very much, time2roll and DrewE.

[DrewE]

It does look to me like CCA, though it's not the easiest to tell from a picture. It generally is possible to figure out by weight as well; aluminum is considerably less dense than copper.

[time2roll]

I think you want #2 or better so it should be 1/4" or more in diameter.

[Naio]

Hi folks, I'm back again and sure would appreciate a little more advice.

Do you think this is CCA cable? Would it be a bad idea to use it for my power cables to my motor?

Thank you so much, all of you:)

[Naio]

Update:

I waited all day by the mailbox for the FedEx truck, got my motor, put it on in the dark. Without a load it was fine, but as soon as I put a small load on it, it had weak power and smoke started coming out. Not a good motor I guess.

Putting the sprocket on the D shaped shaft worked out fine, though!

It looks like I'll be taking the good motor apart tomorrow, to see if I can mess with it myself and not have to send it off to the guy. I don't want to be without any motor.

For those who are worried about my cabling, my cables did overheat when the motor overheated, and I want to replace them. My friend here where I'm staying gave me some. They are unmarked, but fatter than my slightly toasted 6-gauge.

I'm going to figure out how to post a picture of the cut end, though, because it is a silvery color. I'm wondering if they might be that copper coated aluminum stuff.

[Dusty_R]

On your wiring and fuses.
Be sure that the wire and fuses are sized to your machine.
On the sprocket.
Check out Browning's pulleys/sprockets. They have a system that use a shaft squeezing system, It's hard to explain. Do a quick search, not hard to find.

Dusty

[Naio]

I guess I could put the set screw at the edge of the flat part, and then it wouldn't have to be longer

[Naio]

Ohhh.... yes, now that I have found the picture of my sprocket, I remember from installing it that those set screws were tiny little nubbins. I don't have access to a hardware store here, so I guess I will see if I have a screw in my collection that fits, that is longer.

As for the second part, after reading your translation about nine times I finally understood, I think :-). The concern is about the body of the sprocket, above the keyway, where it is tapped for the set screw: the sideways pressure on a longer screw going into the flat part of the D could damage that end of that tapped section.

Yes I think that is definitely something that could happen. Not sure what I could do about it, other than get a spare sprocket.

What am I going to do if I don't have a longer screw? I can put the motor shaft in a vise and try to make a couple of dimples for the screws on the curved part of the shaft. But I imagine the shaft is made out of some super hard metal, and it's not like I have a drill press.

[wnjj]

Naio wrote:

STBRetired wrote:
Make sure you use a long enough set screw that you don't have to worry about ripping out the last thread on the sprocket. Also verify that the keyway in the sprocket has been drilled all the way through so that the set screw does not damage the keyway.

I'm sorry, I don't really understand what you're saying. Especially the second part.


I found my sprocket: This is the one I currently have on the keyed shaft, and that I want to try to put on the D shaped shaft. I see this place is still selling them, so I can get another one.

http://www.staton-inc.com/store/index.php?p=product&id=1958

For the first part, I think he’s concerned that if you wind a set screw that normally stops against a key but now has to reach the flat of the D, it may be too short to engage enough threads in the sprocket.

For the second part, if the set screw is tapered at all, the outermost edges of the threads in the sprocket as they head into the center bore may not be completely clear of metal. So if you now thread a longer set screw completely through the sprocket into the D area it could flare the key surface a bit.

[Naio]

pianotuna wrote:
Naio,

Great sleuthing on finding a "spare". I'd certain buy while you still can.

I did buy a spare when I bought that one, but somehow it didn't make it into the van. I think I'll buy a third one.

But the one I'm saying is virtually irreplaceable, that's a different story. Getting a 3D image of it sounds like a good idea. Of course taking it off would be a giant pain. It's held on by a whole lot of bolts.

[pianotuna]

Naio,

Great sleuthing on finding a "spare". I'd certain buy while you still can.

[Naio]

STBRetired wrote:
Make sure you use a long enough set screw that you don't have to worry about ripping out the last thread on the sprocket. Also verify that the keyway in the sprocket has been drilled all the way through so that the set screw does not damage the keyway.

I'm sorry, I don't really understand what you're saying. Especially the second part.


I found my sprocket: This is the one I currently have on the keyed shaft, and that I want to try to put on the D shaped shaft. I see this place is still selling them, so I can get another one.

http://www.staton-inc.com/store/index.php?p=product&id=1958

[STBRetired]

Make sure you use a long enough set screw that you don't have to worry about ripping out the last thread on the sprocket. Also verify that the keyway in the sprocket has been drilled all the way through so that the set screw does not damage the keyway.

[Naio]

pigman1 wrote:
Are you trying to keep the D shaft on the temporary motor untouched? If NOT, I'd have a machine shop cut a keyway in that temporary motor shaft opposite the D flat. Then have them make a piece that would fill the open D area where the temporary shaft and the sprocket come together. Finally, a dimple on the insert piece that your set screw would mate into.

If you don't want to cut a keyway in the temporary motor shaft, a keyway could be cut into the piece you have made to fill the D area. Depending on how thick that piece is, the D piece may split at the keyway when high motor torque is supplied, but even if it cracked, it should stay in place if you make the fill piece to tight tolerances. If you use this solution I'd make it so tight I had to drive the key and the D shaped fill in piece on to the shaft. A snug interference fit.

My choice would be the first case. If you had to use the temp motor shaft for a matching sprocket, an open keyway opposite the D flat wouldn't cause any problems.

This sounds very much like the right way to do it. I suspect it would take longer than rebuilding the motor, though. But after I get my primary motor rebuilt, I might try to get a shaft modification like this for my backup motor. For next time!

thank you, opnspaces, for the detailed suggestions. And thank you to everyone else! If anyone has any more thoughts, I would very much like to hear them.

I THINK the sprocket in question has two set screws. I'm not completely sure, and I'm not there right now. I don't know if one of them is pointed.

Go George Jetson 🙂