Best way to mount a timing pulley on stepper shaft?

[MaxTheModder]

I am planning my cnc for months now....
Today i came to one little problem:

I decided to double the resolution of my ball screws (with 5mm pitch) by a timing pulley/belt mounted to the stepper motor with 8mm shaft. (20/40 tooth setup)

The stepper motor is planned to have at least 1.5 Nm but i maybe will buy 3 Nm because i would be able to use it for bigger projects later...

So now I think about how to get the pulleys on my stepper motor and the ball scrow mounted correctly...

The timing pulley I have planned for now will be mounted with just one set screw pushing on the shaft.

But i dont really thhink that will hold the force - 3 Nm of torque means 750N of force that the set screw has to hold
- and that seems a bit high for me.

Do you know another good method to mount them correctly?
- maybe with extra screw lock glue?

I would get 3x 20 tooth and 3x 40 tooth with 3x timing belt for 100€ (130 USD) shipped directly from my country. Both polleys are made out of aluminium.

Is that price good or can you show me where i can get them cheaper?

I´m sorry for my English - i hope you are able to understand what i mean

grz Max

[mactec54]

MaxTheModder

You can use a small roll pin,Going right through, Or make a Dutch key, were you just drill the End /centre line of your of your shaft & pulley, this then works like a key way, You then put a round tight pin in the drilled Half grove, This works just like a key, & is ideal for small shaft's

[UUU]

Drill right through, roll pin. This is how the pulleys were fitted on my Emco. and I did the same when fitting new steppers.

[MaxTheModder]

thx for replies!

so you say i should just drill a hole trough the shaft and the pulley and put a metal pin in it? Do you have any pictures showing that?

[mactec54]

MaxTheModder

Here is a photo of the pin, You can drill right through as I said in my first post, but this weakens the small shafts, The round key is better idea

Emco did use this on there low power motors, but not on the higher power motors they used keys

Here is some more information for your belts/ pulleys https://sdp-si.com/eStore/

[MaxTheModder]

ok thank you - will that pin hold completely itself?
sorry but i dont know what you mean with round key??

[UUU]

I can't really get at the parts now they're installed. But have a look at this link where you see someone drilling a motor shaft for a roll pin.

CNCCookbook: IH Mill CNC Home

Now he's using an adaptor to mount his pulley on the motor. In my case the pulley is directly onto the motor shaft, it's a 6mm one, and I drilled straight through the pulley and shaft together. Also my hole goes through the working part of the pulley, where the belt goes, so I just filed the edges of the hole clean after drilling.

[UUU]

And....

....yes the roll pin compresses in diameter as you push it in the hole, so it fits tight.

[mactec54]

MaxTheModder

This should help

[MaxTheModder]

wow thx for your fast replies!

ok now it is all clear to me - i didnt know what "key" means (my technical english is very very basic)

But i think the round key method from mactec54 is a bit hard to machine for me.

The method of UUU with the pin seems to be simple but i dont think that it is really stronger than the normal set screw.

Maybe it would be also easy to drill a bit into the shaft that the set screw gets better hold. I think that would be enough

what do you thnik is the best and easiest method?

[harryn]

I would at least try to make a sort of "flat spot" on the shaft for the set screws to lock into, even with a file if necessary. A smooth, hard shaft is very difficult for set screws to hold position on.

Two set screws are better than one.

Best, is possibly the collet style holders that use a sort of collet like design to lock the pulley to the shaft. These tend to spread out the force around the shaft. They aren't cheap though, and force the pulley to be larger diameter than you might normally use.