Dual-diameter 6mm & 12mm motor shaft?

[erth64net]

I've got a Scorpion 4025-16, which is designed for a 6mm shaft (slight press-fit when installed).

The dilemma is; the freewheel/clutch-bearing that I'm eyeing needs to slide onto a 12mm shaft, so...I'm seeking a 125mm long shaft, where the first 90mm is 6mm in diameter and the final 35mm of length is 12mm in diameter.

I have a small 4x5 metal lathe, but have never tried turning shafts, especially ones needing a "slight" press-fit; does anyone have any idea what the success rate is for such an attempt (I've got, maybe, 50 hours experience using a lathe), and/or if there's a machinist/shop/store out there who has more skills and better equipment for such a task?

[Miles]

Gregg,

Wouldn't it be easier just to sleeve the original shaft?

What kind of clutch-bearing is it?

[buzzfirst]

Hello, If you have centers for the headstock and tailstock it should be doable to turn a shaft that length on your 4x machine. Center drill each end of a piece of stock, mount the stock between centers, and turn the 12mm part then turn the 6mm part. When turning between centers you can remove and remount the part without losing your center. You could get the 6mm part close (but big) and test fit it, put it back on the lathe and take another small amount either with a tool bit, file, or emery paper, repeat until done. Do you have an outside micrometer or at least a caliper for outside measurement? Option 2... If you only have a 3 jaw chuck mount a piece of oversize stock, turn the entire needed length to 12mm then turn the 6mm end on the tailstock end of the part. That way you can test fit the 6mm end in your motor without removing the part and everything will stay centered and circular. Start with a good piece of known steel or you may just waste your time. 1/2 inch drill rod would be perfect as you would have just enough to true the rod up in the chuck before you got to 12 mm and it is easily hardened after you get the dimensions correct.

[erth64net]

Gregg,

Wouldn't it be easier just to sleeve the original shaft?

Maybe, but it's not keyed, so I worry about slippage; this particular design is hopefully where I can say "done", and finally give the whole setup a few months of solid "reliable" usage...

What kind of clutch-bearing is it?

This one: http://www.vxb.com/page/bearings/PROD/O ... gs/Kit8177

[erth64net]

Hello, If you have centers for the headstock and tailstock it should be doable to turn a shaft that length on your 4x machine. Center drill each end of a piece of stock, mount the stock between centers, and turn the 12mm part then turn the 6mm part. When turning between centers you can remove and remount the part without losing your center. You could get the 6mm part close (but big) and test fit it, put it back on the lathe and take another small amount either with a tool bit, file, or emery paper, repeat until done. Do you have an outside micrometer or at least a caliper for outside measurement? Option 2... If you only have a 3 jaw chuck mount a piece of oversize stock, turn the entire needed length to 12mm then turn the 6mm end on the tailstock end of the part. That way you can test fit the 6mm end in your motor without removing the part and everything will stay centered and circular. Start with a good piece of known steel or you may just waste your time. 1/2 inch drill rod would be perfect as you would have just enough to true the rod up in the chuck before you got to 12 mm and it is easily hardened after you get the dimensions correct.

Well, it's a 3 jaw self-centering chuck...and from your description, it sounds like drill rod would work fine. I suspected drill rod would be alright, so thank you for taking the time to explain.

Further, I've got a caliper (micrometer is on the xmas wishlist )...but didn't really count on using it for close measurements; just eyeballing things, and then test fitting as I neared completion...sounds like I'm on the right track.

[Miles]

Maybe, but it's not keyed, so I worry about slippage; this particular design is hopefully where I can say "done", and finally give the whole setup a few months of solid "reliable" usage...

You'll get the sprag clutch with a keyway, then?

[erth64net]

Maybe, but it's not keyed, so I worry about slippage; this particular design is hopefully where I can say "done", and finally give the whole setup a few months of solid "reliable" usage...

You'll get the sprag clutch with a keyway, then?

Sure, I guess I can buy another sprag clutch...

Seriously though - while there's a few places with related spec sheets online, I can't find anyone who'd actually sell small quantities (ie: 1 or 2) of the keyed option.

[buzzfirst]

Hey Erth, one more thing about that shaft. It would probably be a good idea to leave a rounded transition between the 12mm portion and the 6mm part of the shaft. I guess a fillet would be more descriptive, anyway just try not to leave a 90 degree sharp inside corner between the two sections of shaft. There is only 6mm of steel and if it breaks it will break at the transition if it is sharp. I hope that made sense.

[Miles]

Making a new shaft for the motor would be a nice turning exercise but the easiest solution would be to make a sleeve and bond it on with anaerobic adhesive and then bond the clutch to the sleeve.

I don't know about sources in the States but I was able to get one with an internal keyway, easily enough, in the UK. Cost will probably be 4 or 5 times that of the Chinese one, though..... Have you tried this company: http://www.marland.com/index.html ?

[erth64net]

Thanks for all the pointers and tips!

I do want to turn a shaft, but am inclined towards using a sleeve and anaerobic adhesive for the short-term...can't make up my mind at this moment

Just to better "illustrate" what I'm attempting to mount:

HTD pulley mated with sprag clutch

IMG_4965.jpg (51.09 KiB) Viewed 1060 times

HTD pulley mated with sprag clutch mounted on motor shaft

IMG_4970.jpg (44.81 KiB) Viewed 1051 times

[Miles]

can't make up my mind at this moment

See how you feel in the New Year?

[buzzfirst]

Turned shaft = easy repair or replacement ,, Adhesive = not so much... Good luck with it whichever way you go!

[Miles]

Turned shaft = easy repair or replacement ,, Adhesive = not so much...

How so?

[GGoodrum]

Wouldn't it be easier to drill/tap a couple of set screw holes, and the use a 12mm-to-6mm bore reducer from SDP-SI?

-- Gary

[buzzfirst]

With a turned shaft you would simply loosen the set screws and disassemble. With adhesive you would either have to press it apart, pound it apart or heat enough to soften the adhesive(which would wreak havoc on the bearing seals). Even though the hammer method is more fun you would still have to hold the bearing while hitting the shaft. Once apart it would have to be cleaned of all the old adhesive and reset in adhesive.

[Miles]

With a turned shaft you would simply loosen the set screws and disassemble. With adhesive you would either have to press it apart, pound it apart or heat enough to soften the adhesive(which would wreak havoc on the bearing seals). Even though the hammer method is more fun you would still have to hold the bearing while hitting the shaft. Once apart it would have to be cleaned of all the old adhesive and reset in adhesive.

I've heated using a controlled soldering iron on the shaft, with the joint under pressure.

I agree a new shaft would be the way to go if you were going to do a keyway fixing for the sprag clutch. You can't fix the sprag clutch to a new shaft with set screws.

[Miles]

Gregg,

Looking at your photo it seems to me that keeping the existing shaft makes more sense.

You could make an adapter for the sprag clutch which fixes onto the original shaft with set screws - the sprag clutch pulley assembly would be bonded to the adapter. You'll need to bore out the pulley and put a needle roller bearing inside it, though, I think.