threaded shaft for removable hub?

[yadnom1973]

I have a part that I have been working on and there is a roller that has to be changed every now and again for different ones. I was trying to think of a way to go about this and landed on the idea of threading the hub and threading the shaft so the hub would be screwed onto the shaft flush up against a shoulder then a split threaded shaft collar would be screwed on and tightened up to fix it all in place.

The shaft is steel; the hub is aluminium and the collar steel. The hub, shaft and collar are all M14 thread.

It seems like a good idea to me but I can’t find any examples of this anywhere so I’m beginning to think that there must be something wrong with it.

The only problem I can think of is that the whole lot would work undone but those shaft collars tighten down pretty solidly, that’s an M5 bolt in it.

I was thinking of using the same idea to fit a small gear I have to a relatively large shaft where the bore is bigger than normal.

Any advise on why this is a bad idea would be appreciated and any

alternative ideas most welcome

 

[yadnom1973]

That's supposed to be a screen grab at the end to explain what I'm talking about but I'm not sure that picture worked properly, here's a link:

https://www.flickr.com/photos/72122298@N04/36198465616/in/dateposted-public/

 

[yadnom1973]

I forgot to mention a pretty vital fact, I thought it was apparent from the drawing and description but maybe I'd better clarify that the rollers/gears are fixed to the shaft, the shaft sits in bearings.

 

[kvom]

Why does the shaft need to be threaded? Pressure from the collar and the shoulder would keep the hub from rotating.

 

[yadnom1973]

Pressure from the hub and the shoulder? I'm not sure I understand how that would have any effect, maybe if it was a serrated side on the hub and the collar like locking plates but as it is they are both flat metal surfaces so there wouldn't even be much friction, and without the thread I'm not sure how pressure would be applied before locking the collar in place.

Maybe my explanation wasn't very clear. If you look at the picture you'll see that without the thread it would be a plain 13 or 14mm steel shaft and a plain bore of the same diameter.There is no connection between the shoulder and the hub or the hub and the collar apart from being fitted flush up against each other, they would hold the roller in position axially on the shaft but without a key or a splined shaft and hub or just some locktight the roller will rotates free of the shaft as soon as some torque is applied.

 

[bazmak]

The principle is sound and should work well.A std practice is to lock the threaded collar with a grub screw,which i avoid as it can damage the thread

 

[yadnom1973]

That's right, I need to avoid damaging the threads as these need to be removed and replaced at different times. These are not the collars with the grub screws anyhow, these collars are the split type with a bolt through to tighten them onto the shaft:

http://www.wdsltd.co.uk/product/4772/semi-split-shaft-collar-304-stainless-steel-wds-827/

I looked at trying to use a boss with a grub screw passing through or into the shaft but the hubs of the rollers and the gear, it's a belt pulley actually, are quite thin as it's such as small hub/pulley on such a large shaft there is very little material to work with.