Tightening Axle Bolt

[upward]

Been using my MXUS DD Kit from Cellman for about 18 months. Got a flat tire yesterday and changed it. When tightening the axle bolt, it would not tighten. After getting nearly tight, the nut would get loose again after turning it a bit more. I was able to get around the issue by removing the lock washer and tightening the nut again.

Questions:
1) Does it sound like I stripped part of my axle by over-tightening the nut? Was I able to tighten by moving to another part of the axle that was not stripped by removing the lock washer?
2) Or more likely that I need a new flanged nut? Believe it is M14 size, but not sure of pitch: M14-1.0 or M14-1.5 or M14-2.0 or other? Anyone know?

 

[Tench]

We cant tell you which it is, you will need to remove the nut to examine it and the axle thread, if removing the washer got the nut to tighten again odds are that it is the axle thread that is damaged. Experience tells me that it is most likely to be a combination of both nut and axle though.

 

[deffx]

From your description sounds like the axle threads

My Mac is the same, stripped on the wire exit/grooved side

Chinese steel made from cheese

Can't help you on the thread and pitch sorry

 

[dogman dan]

Yep, unfortunately you stripped it. You have a single thread holding it now, the thickness of a washer. If you have the length of axle to do it, stack more washers and get a new nut on more good threads.

Or, perhaps it's time to build yourself a pinch dropout. Perfect for stripped axles.

 

[MadRhino]

Yep, no matter how you build (torque plates, pinch or custom dropouts), you should not rely on the axle nuts to hold your motor wheel.

 

[NeilP]

Or get your self an M12 x 1.50 die and some M12Locknuts

you will be able to run the M12 die over the stripped portion, and due to the flats and alreadystripped threads, you will not need to reduce the diameter.

I know it works..I did it byaccident last week when I picked up the wrong die to clean the threads on my axle. They had already partly stripped and I want to run the die over to clean them up...but used an M12 rather than M14

Advantage is that now there is more thread holdign the nut, as there are threads on part of the flat section too.

 

[teklektik]

The ES thread: "BMC Hub Motor - customer support - stripped threads" has simple repair strategy that seems quite effective and requires minimal tools/skill.

 

[upward]

Thanks for the replies everyone. Really appreciate it.

First strategy: I'm going to pickup some M14 washers from the hardware store after work and try to stack them to use another part of the axle. Then stopping by the auto parts store to get a M14 x 1.5 thicker nut that will grab more threads then the original nut that came with the kit. The original nut seemed kind of soft as the edges were rounding. Also ordered some nord-lock washers so I won't have to over-tighten the nut in the future.

Second strategy: Will look into the M20 sleeve solution teklektik suggested. Looks like a low level of difficulty. Will also look into the solution form NeilP if the other methods don't work.

Third strategy: If all else fails, I will buy another hub motor in the wheel. Would use the automotive nuts with nord-lock washers to minimize the chances of over-tightening again.

Will provide updates as things progress.

 

[Punx0r]

Beware that a standard M14 thread is 1.75mm pitch. The 1.5mm pitch is a bit of a speciality and you might find it difficult to find one at a non-specialist store.

A visual inspection of the original nut may prove it's ok. Just see that all the threads are sharp and equally spaced. If they're squared off, or the first thread is pushed up to the second then it's damaged.

 

[dogman dan]

I've rethreaded axles before too, and even using the same size as before might help, then use a longer nut to grab more threads.

Never like new though.

Bet Neil does a hell of a lot better job using the threading tool than I do.

 

[alsmith]

Beware that a standard M14 thread is 1.75mm pitch. The 1.5mm pitch is a bit of a speciality and you might find it difficult to find one at a non-specialist store.

A visual inspection of the original nut may prove it's ok. Just see that all the threads are sharp and equally spaced. If they're squared off, or the first thread is pushed up to the second then it's damaged.

A standard M14 thread is 2mm pitch, not 1.75mm
The Crystalyte M14 thread is 1.5mm pitch. This is called Medium Fine.
Other 14mm pitches are 1.25mm, 1.0mm, 0.75mm, 0.5mm. There is not a standard 14mm thread with a 1.75mm thread.

 

[upward]

I was able to find M14 Washers from Ace hardware and an M14 x 1.5 bolt from the auto store. Needed two washers to clear the fender bolts because the nut I bought needs the hex part facing towards the motor. The other side of the nut has a narrow surface.

The old nut didn't go on after a few turns without the help of a wrench and the same happened for the new nut. But it didn't get any easier as I progressed. I backed the nut out and I found circular (spiral) metal shavings. Not sure if from the nut or from the axle but I did something not right. Could have been the wrong pitch of the nut. Good news is that the nut goes on easier now, although still requires a wrench to move it along the axle. The nut is also bigger so had to adjust my torque arm to fit.

In all, the nut is grabbing significantly more threads and is tight. Went for a ride around the block and it's ok but time will tell.
Hoping with my power limited to a modest 1000w on the CA as it has been, that it will hold.

Also received some nord-lock washers today, of course after I was done with the above already. Will hold off installing them and see how the nut holds.
Haven't opened the box yet but I should have a few pair extra (M14 size) so for the folks who tried to help in this thread, pm me if you would like me to send you some: alsmith, dogman, punx0r, tekliktek, NeilP, MadRhino, deffx, tench.
I should have 6 pairs extra (enough for 3 motors on both sides)

 

[Punx0r]

That's a kind offer, but I'm good, thanks

Alsmith, you're quite right about the M14 standard thread pitch, apologies. I knew it wasn't 1.5mm but confused it with M12.