# Coupling a splined shaft



## jackbauer (Jan 12, 2008)

My recently acquired forklift motor has a splined output shaft of outside size 31.45mm. It does not seem to be hardened as it can be filed. Just wondering what you all think is the way to go for coupling this to the clutch center boss? My initial thinking is to bore a piece of 60mm stock to a tight fit on the splines then grind a key way into the shaft or drill the shaft through and put a pin through the whole assembly? Any comments welcome


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## joseph3354 (Apr 2, 2008)

a lot of people use something like this:

http://www.drillspot.com/products/455394/Ust_PL1R_Power_Lock-R-


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## Jimdear2 (Oct 12, 2008)

jackbauer said:


> My recently acquired forklift motor has a splined output shaft of outside size 31.45mm. It does not seem to be hardened as it can be filed. Just wondering what you all think is the way to go for coupling this to the clutch center boss? My initial thinking is to bore a piece of 60mm stock to a tight fit on the splines then grind a key way into the shaft or drill the shaft through and put a pin through the whole assembly? Any comments welcome


Another option might be to remove the armature and have the shaft turned down to a standard size and then keyed. Depending on the root diameter of the spline you might get in at 1 inch or maybe 7/8 inch.

While the armature is out the machinest could also clean up the commutator and you could replace the bearings and brushes if needed and give the motor a thourough cleaning and inspection.

IMHO, drilling the shaft through and cross pining is probably the worst option.

Also look into the possibility of obtaining whatever the spline end engaged into on the Hi Lo. Possibily that component could be refinished or fabricated in to a motor trans adapter.


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## AmpEater (Mar 10, 2008)

I've passed on countless splined motors for just this reason. Who would have thought coupling two shafts could be such an issue? 

Anyway, taper-lock is probably your easiest option (I don't have first-hand experience with these on a spline)...and having it turned down being more complex but a much simpler starting point once it's complete. The most durable coupler would be to find someone to make a matching female spline, but that is also likely the most expensive.


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## jackbauer (Jan 12, 2008)

Having the shaft turned down is a good idea but probably not easy where i live at least on my budget! Looking at the keyless bush idea. Either that or i'll consider grinding a keyway into the shaft. May i ask why the pin is a bad idea?


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## jackbauer (Jan 12, 2008)

i'll make some calls tomorrow to see what keyless bushes i can dig up. I'm going for the clutchless design.


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## Jimdear2 (Oct 12, 2008)

jackbauer said:


> Having the shaft turned down is a good idea but probably not easy where i live at least on my budget! Looking at the keyless bush idea. Either that or i'll consider grinding a keyway into the shaft. May i ask why the pin is a bad idea?


I may be proven wrong but I beleive that removing that much material theough the cross section will weaken the shaft. Plus the hole will become a stress point concentrator.


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## toddshotrods (Feb 10, 2009)

Jimdear2 said:


> I may be proven wrong but I beleive that removing that much material theough the cross section will weaken the shaft. Plus the hole will become a stress point concentrator.


I think that's right. I can't remember where I saw it but I learned that researching for building my race chassis. I was looking at some stuff on steering linkage and they advised against pinning the steering shaft. They gave some numbers on the reduction in strength with drilling the shaft and it was significant.

I just did a search for the spline count and diameter of my motor's output shaft and found a place that sold tractor PTO and clutch discs. I eventually ordered the PTO disc and it is a perfect fit. Here's the place I found mine.


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## Drew (Jul 26, 2009)

Why not make a shaft extension with a matching female spline, if you get the OD of the spline and the tooth count then you'll probably find that its a standard part and so you can just get an adaptor plate built with that spline at the center.


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## scarab (Jul 3, 2008)

Have a look at ELECTRIC LEMON coupler using a cut down clutch plate and a female coupler to suit your motor shaft


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## DIYguy (Sep 18, 2008)

I had this same issue. I did what Jimdear suggests. I rebuilt the motor, it was my first and only electric motor refurb and it was pretty straight forward. Removing the armature was simple. I had mine turned and keyed where I work... but I don't believe this is an expensive proposition at all, as it didn't take long. Actually, I had both ends done. Also cleaned up the brush contact area while it was on the lathe.

I have some pics on my thread... 

Regards,
Gary


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## Harold in CR (Sep 8, 2008)

This idea may sound strange, but, give it some thought, before shooting it down.

You guys ever hear of, or use, Devcon Filler ??? It is a metal embedded "Putty" of sorts, that will fill gaps in metal, to hold new bushings in place, on articulated front loader arms. I know this to be fact. I helped do this project.

Regarding the splined shaft, why not fill the grooves with that "metal Putty", and lightly grind it smooth with the splines, by running the motor on low voltage ??

It is NOT as difficult as it sounds. Clean the shaft with brake cleaner, so the stuff sticks. I guarantee it will NOT come out of the compressed collar that is used for the coupling device. You will be tightening ON the splines, as well as ON the metal filler. 

Google Devcon for specs. It is truly good stuff.


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## jackbauer (Jan 12, 2008)

thanks for the suggestions guys and to be honest i can now see the problem with the pin idea. I'm looking into the locking bush and if not successful i will grind a keyway into the shaft and make my own sleeve to fit. Anyone see a problem with that?

Taking it to an engineering shop to be turned and keyed is of course the best idea and not a problem in the US but a totally different matter in Ireland!


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## Harold in CR (Sep 8, 2008)

The reason I suggested looking into the Devcon, is, I'm not a believer in a coupling riding on top of splines. IF it ever gets ANY play, it's like having a file in there working on wallering out the mating surfaces.


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## jackbauer (Jan 12, 2008)

Ok just had a play in the workshop. Took a standard 28mm taper lock bush and a weld-on hub. Put a small strip of metal into the gap in the bush and tightened it into the hub. Mounted the whole affair in the lathe and bored it out to 31.35mm. Opened up , removed the strip and tightened it onto the shaft as seen. Rock solid and seems to run true.

I know i'm weakening the bush etc but just might be onto something. I can easilly source a taper lock shaft coupler and 28mm bushes. All I then need to do , in theory at least , is to carefully grind a keyway into the shaft and fit a bored out coupler. Whatcha think?


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## ga2500ev (Apr 20, 2008)

scarab said:


> Have a look at ELECTRIC LEMON coupler using a cut down clutch plate and a female coupler to suit your motor shaft


The Lemon did not have a splined shaft. It was keyed.

I'm in about the same situation at the OP, except that I do have a female sleeve that fits over the splined shaft.

Looking for a solution to mate to the transmission of my 1992 Geo Metro.

ga2500ev


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## jackbauer (Jan 12, 2008)

If you have the female then i'd suggest boring a piece of round stock to a tight press fit then weld it in there with a 29/9 electrode.


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## DIYguy (Sep 18, 2008)

jackbauer said:


> Ok just had a play in the workshop. Took a standard 28mm taper lock bush and a weld-on hub. Put a small strip of metal into the gap in the bush and tightened it into the hub. Mounted the whole affair in the lathe and bored it out to 31.35mm. Opened up , removed the strip and tightened it onto the shaft as seen. Rock solid and seems to run true.
> 
> I know i'm weakening the bush etc but just might be onto something. I can easilly source a taper lock shaft coupler and 28mm bushes. All I then need to do , in theory at least , is to carefully grind a keyway into the shaft and fit a bored out coupler. Whatcha think?


Personally, I think it is not a good idea what you are suggesting. This is not an an application for epoxy, hand grinding, etc. Do it right man, you won't regret it. 
I have a hard time believing you can not get this simple machine work done in Ireland. You need a key and you need it done right. Don't mess with hand fit anything. It is not an "Engineering shop" you need... any decent machine shop will do this for you with a few hours work. Britain is a powerhouse of trades. Where do you think all of our tradesmen came from? When I started in the auto industry as a young man in Engineering, 75% of our technical people were trained/educated in Britain.. England/Scotland/Whales. I've heard Ireland has a lot of IT stuff...but if you have to travel a little, it's not that bad.

You don't have to agree... but you asked, and it's my two cents.


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## jackbauer (Jan 12, 2008)

Wouldn't be a problem at all if I lived in Britan but I don't I fully appreciate your point and if i had the option i'd do it exactly as you said. Very few if any small engineering works exist today in Ireland. We only have ourselves to thank for that as it was deemed by the high and mighty that Ireland was "too good" for that kind of nasty messy work. Those organisiations that have the capability of doing such work will either a)not deal with me because i'm not some massive company with endless pockets or b) don't want the work. I have telephoned several places this week and the response has varied from flat refusal to:
"Splined shaft? that cant be turned"
"why?"
"Its hardned"
"well i can file it and can't you use a carbide cutter"
"eh....."

This is why I do as much of my own work as possible and probably why no ev conversions worth spit have been done here. Now I do have a 5x24 lathe and a full sized turret milling machine so would you feel better if i said I'd mill the key slot?


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## Jimdear2 (Oct 12, 2008)

jackbauer said:


> This is why I do as much of my own work as possible and probably why no ev conversions worth spit have been done here. Now I do have a 5x24 lathe and a full sized turret milling machine so would you feel better if i said I'd mill the key slot?


Jack,

A few suggestions/questions.

Have you checked to see if your lathe will swing the armature once it is removed from the motor. Then you do the shaft

Have you checked for motor rebuilding shops in Ireland. They should have a lathe that could cut down the shaft,

How much would it cost to ship just the armature to a shop in GB

A mill to do the key slot makes ALL the difference. 

The torque transfers through the key so as long as there is adaquate support metal left in the shaft key slot for that transfer to occure you should be OK. The remainder of the shsft carries no real load it just keeps the coupler concentric.

Lastly, check with the source you got your motor from. That spline shaft did engage into something. Possibly that something could be re-engineered into a good coupler.

Hope something above helps.


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## DIYguy (Sep 18, 2008)

jackbauer said:


> Wouldn't be a problem at all if I lived in Britan but I don't I fully appreciate your point and if i had the option i'd do it exactly as you said. Very few if any small engineering works exist today in Ireland. We only have ourselves to thank for that as it was deemed by the high and mighty that Ireland was "too good" for that kind of nasty messy work. Those organisiations that have the capability of doing such work will either a)not deal with me because i'm not some massive company with endless pockets or b) don't want the work. I have telephoned several places this week and the response has varied from flat refusal to:
> "Splined shaft? that cant be turned"
> "why?"
> "Its hardned"
> ...


Wow, that's a damn shame. It's no problem to machine. it may be case hardened at best.... a carbide has no problem with it. I'll bet high speed still will do it. Either way skim it lightly at first as it will vibrate a bit till you get past the splines.

A mill to cut the key way? hell yes! ur laughing.

Good points by Jim... never know... 

good luck.


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## DIYguy (Sep 18, 2008)

My splined shaft before.... and after......

...and the motor before and after....


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## jackbauer (Jan 12, 2008)

I'm pretty sure i can swing the armature only problem will be how i set it up. I can probably remove the comm end bearing and hold that in the chuck. I can then grab the drive end bearing in the fixed steady and hopefully have enough travel left to turn off the splines.
I'm a bit afraid is all

I'll do a few measurments tonight. Would a HSS endmill be ok for the keyway or should i go carbide?

DIYguy your making me jealous Thats how i want my motor shaft to look!


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## DIYguy (Sep 18, 2008)

hehe, sorry man. I think HSS end mill will work just fine... as I said, the splines may be case hardened...but after you buzz those off, the end-mill should have no probs carving a groove in that shaft.....


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## DIYguy (Sep 18, 2008)

jackbauer said:


> I'm pretty sure i can swing the armature only problem will be how i set it up. I can probably remove the comm end bearing and hold that in the chuck. I can then grab the drive end bearing in the fixed steady and hopefully have enough travel left to turn off the splines.
> I'm a bit afraid is all


Can't u use a live centre on the drive end? There should be a nice chamfered hole there already??


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## jackbauer (Jan 12, 2008)

Yeh the shaft is drilled and tapped m12 on the drive end that would fit the center. Is there any special procedure for dismantling a dc motor? Only ever done ac induction types.


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## jackbauer (Jan 12, 2008)

Ok bit the bullet and puled out the armature as per instructions on jim's webiste. Nearly loaded my pants a few times but here she is:

this ain't no cordless drill

I'm gonna hold fire and talk to a few motor rewind companies next week. The arm is seriously heavy and i can hardly lift the thing. Biggest fear would be it flying out of the lathe.


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## jackbauer (Jan 12, 2008)

Ok decided to do a few experiments on the shaft coupling side of the plan. Firstly accurately measured the outside diameter of the splines at 31.36mm. Next took some 60mm steel stock and turned it outside to 55mm and made an inside bore of 31.30mm. This was just a test piece and it would go on the shaft with some pressure. Less than .02mm run out on the dial gauge. One idea i have if worst comes to the worst is to key the outside of this bush , put it on the shaft and weld it front and back with a 29/9 welding rod.

I had a pilot bore jaw coupler to hand so i chucked it on the lathe (difficult as it seems to be just cast and no two surfaces were true running) and bored it to 31.32mm. Tapped onto the shaft beautifull and its nice and tight. I hate machining cast iron Anyway possible idea here is to key motor shaft and coupler. Job done. Any thoughts or comments welcome. Remember guys i'm on a budget here


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## fritzgutten (Jul 4, 2009)

well, i dont know what kind of flac i'll get for this, but i've done keyways on the lathe, using the carriage as a metal shaper. with the lathe not running....der  and mounting a straight ground HSS tool bit on its side, pushing along the long axis of the bit. scraping the key seat .005" or so per pass.
i could mock it up in my lathe if my verbal skills are lacking. one problem with this method is that it may be hard on the carriage. but you dont worry to much about that when you pulled your lathe out of the junk pile.


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## jackbauer (Jan 12, 2008)

The plan is to take the coupler to a plastic injection moulding company who will be able to key it with a wire eroder. So they tell me anyway! Fingers crossed. I had thought about the lathe shaper idea as a last resort.


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## fritzgutten (Jul 4, 2009)

Jack, 
thats great, hope they do well for you!
fred


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## jackbauer (Jan 12, 2008)

Success at last!
http://www.diyelectriccar.com/forums/showpost.php?p=136025&postcount=17


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## bazou (Sep 11, 2009)

toddshotrods said:


> I think that's right. I can't remember where I saw it but I learned that researching for building my race chassis. I was looking at some stuff on steering linkage and they advised against pinning the steering shaft. They gave some numbers on the reduction in strength with drilling the shaft and it was significant.
> 
> I just did a search for the spline count and diameter of my motor's output shaft and found a place that sold tractor PTO and clutch discs. I eventually ordered the PTO disc and it is a perfect fit. Here's the place I found mine.


Hi Todd,
I'm thinking about a build that will inevitably involve a splined shaft (forklift motor). Would you mind posting a picture of your assembly and a link to the exact part, as I'm not sure exactly what you got.

Thanks!!


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## bazou (Sep 11, 2009)

jackbauer said:


> Success at last!
> http://www.diyelectriccar.com/forums/showpost.php?p=136025&postcount=17


 Great!
Just a quick question, how much did it cost? Do you think would it be cheaper to do it DIYGuy's way if available ? (turning the shaft then keying it?)

Also, another newbie question: Exactly what is the part the that fits on the keyed shaft? I understand they are called jaw couplers? Did you get 2 ,one for the motor shaft, one for transmission shaft? If 2, how do they connect together? Welded? 

And finally, how did you choose them? 


Just to make it easier for me to understand, can you confirm (and complete) this :

motor shaft - (keyed and screwed to) -- jaw coupler 1 -- (welded to?) -- jaw couplers 2 -- (keyed and screwed to) transmission shaft


Sorry for all the newbie question, and thanks again!


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## bazou (Sep 11, 2009)

.......... edited out


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## jackbauer (Jan 12, 2008)

My problem was that if i had turned the splines off the shaft I would not have had enough "meat" left to key the shaft as it was drilled and tapped m12. Instead I bored one end of the coupler to a nice tight tap fit on the splines (.03mm undersize) Then had an engineering shop key the coupler and shaft. If you have a solid shaft i'd go the way of turning it down and keying. The coupler i used is called a pilot bore 110 hrc coupler and I had it to hand from a previous project. As to whether it will work or break I don't know but it was free so worth a try. Most coupler manufacturers specify torque and speed so best to do the maths first unlike me

Unfortunatly my coupler is cast iron so i didn't want to risk welding even with a nickel rod as cast does not weld very well even at the best of times. So I drilled and tapped 4 x m8 holes and fitted ht stainless allen bolts.
http://www.diyelectriccar.com/forums/showpost.php?p=137109&postcount=31
Have a read through my build thread.


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## bazou (Sep 11, 2009)

jackbauer said:


> My problem was that if i had turned the splines off the shaft I would not have had enough "meat" left to key the shaft as it was drilled and tapped m12. Instead I bored one end of the coupler to a nice tight tap fit on the splines (.03mm undersize) Then had an engineering shop key the coupler and shaft. If you have a solid shaft i'd go the way of turning it down and keying. The coupler i used is called a pilot bore 110 hrc coupler and I had it to hand from a previous project. As to whether it will work or break I don't know but it was free so worth a try. Most coupler manufacturers specify torque and speed so best to do the maths first unlike me
> 
> Unfortunatly my coupler is cast iron so i didn't want to risk welding even with a nickel rod as cast does not weld very well even at the best of times. So I drilled and tapped 4 x m8 holes and fitted ht stainless allen bolts.
> http://www.diyelectriccar.com/forums/showpost.php?p=137109&postcount=31
> Have a read through my build thread.


Thanks for the precision. I read your build thread, but then again I've done about 20 hours of reading since last Friday, so I've forgot a lot.

You didnt simply have a spline machine in your coupler because it was too expensive right?

Also, someone mentionned getting a tractor PTO disc with matching spline, have you looked into it and discarded it? 

Sorry, I'm juist trying to order the options from best to worst 



Oh, and how large a shaft would be considered as having enough meat to turn ?


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