View Full Version : Stepper shaft size and pulley bore size problem

14-06-2010, 02:39 PM
Hi everyone,

Im continuing to source my parts to copy a design from automatedwoodwork. I have run into a problem sourcing the correct stepper pulleys from the UK.

In one of the pulleys, the pilot hole is larger than the diameter of the stepper shaft. I wonder if anyone has any experience in using a bush or a coupler to increase the shaft diameter in circumstances such as this? I ask becuase I cannot find a supplier for the bushes anywhere. I spoke to a few pulley manufacturers who all said they didnt have an answer to such a problem?

I would change the pulley size but have no idea what the consequences would be :confused:

Man im stressed out..............

Thanks guys.

14-06-2010, 04:22 PM
Creating a bush for this would not be hard but I doubt you'll find an off the shelf solution. You need to find some kind soul that can turn a bush that is a shrink fit into the pulley bore (i.e. goes in when the pulley is hot and bush freezer cold). The bush can then be bored/drilled out to the necessary size. BTW what are the sizes you need and what pulley? It may be that there are other ways to address the problem.

14-06-2010, 04:48 PM
Thanks for the reply.
Im looking for a 12L075, basically a 12 tooth pulley to suit a 075 (19.1mm) belt with a 6.35 or less pilot to suit a nema 23. I really dont understand what consequences changing the pulley will have, I have emailed the designer and waiting for him to get back to me (he is very responsive by the way). He had to use a bush when building his machine too but it was a different size to the one I would have to buy from the UK. I did ask about the bush in the first place and he told me he got it from a local hardware store.

Is it me or do the hardware stores in the USA stock everything!!!!!!

14-06-2010, 05:09 PM
It would appear that 'McMaster-Carr' stock nearly everything the US has ever produced in plastic or metal ... http://www.mcmaster.com

14-06-2010, 05:18 PM
Yes they do, at a price...

14-06-2010, 06:39 PM
Yes and they will no longer ship to the UK.

Due to the ever-increasing complexity of U.S. Export regulations, McMaster-Carr has decided to only accept orders from a few, long-established customers of ours overseas.* We are not able to provide a quote nor can we accept your orders.* We regret any inconvenience this causes you.

Oh dear.......

14-06-2010, 06:45 PM
I tried to order from McMaster Carr just before Christmas and they said they only supply otside the contiguous USA to "specially approved customers or customers they have a long history with". I even tried the Parcels2Go route, having the stuff sent to a drop off address for forwarding in the US and they blocked that too.

Pity as they are a goldmine of hard to get parts.


14-06-2010, 07:42 PM
So you tried to order via the website and send the goods inside america and they blocked it? Wow thats rediculous, I may ask the designer to order the goods on my behalf and then Ill collect via courier instead. Really stupid to have to go around the town like this..........................

14-06-2010, 08:18 PM
Yes, Psiron, exactly that. Because payment was coming from outside the contiguous (so they won't send to Alaska or Hawaii for ex) US, they refused the order, must have so much business they can turn away the rest of the world. Maybe the reccession has had an effect by now and they might accept an order, worth a try I suppose. They wouldn't even let my wife's aunt in Canada order for me. luckily I found automation overstock in the US who had the profile rail I needed and cheaper too. If the designer is willing (and he seems a decent guy), that would be the way to go, either that or source metric equivalents in the UK, these guys are very good: Bearingboys (http://www.bearingboys.co.uk/Bearings-1005-c?gclid=CKeruLeloKICFZtm4wod0k2vtw) they do the pulleys you are after and the belts.

BTW, for your pulleys, just treat them as gears so a 12 tooth small pulley driving a 72 tooth larger pulley would give a 6:1 drive reduction (72/12=6) so you just need to work out the ratios he is using and get the metric equivalent


14-06-2010, 08:54 PM
Thanks Jeff,

Ive managed to find the pulleys but the bore is a problem, I can overcome the problem by getting some bushes machined which isnt a problem, I was looking for a cheaper way though hence the post.

The timing belts are pretty easy to find but the L075 open ended ones aren't. I have contacted a few suppliers by email and waiting for them to come back to me. Hopefully Ill get some prices tomorrow. After looking around more and more I would love to use R&P but I cant afford it. The cutting bed size is important to me as I cut plastic sheet (currently using a hand router which is a nightmare). Therefore I will have to try the belt system first and see how it works out.

Thanks again fella, its so nice to have a forum here in the UK :)

14-06-2010, 09:04 PM
You are welcome. If you can benefit from our mistakes it will save you loads of time and money. I'm not decrying the belt idea, I don't know enough about belts at this length to make an informed comment but the basic machine you have there would be easy to convert to R&P if the belts prove troublesome and you might have earned enough by then to modify. The main thing is go for it, there are so many knowledgeable guys on this forum who've built machines and made all the mistakes, they will keep you straight. Above all, don't be afraid to ask all the questions you want even if they seem daft because they are the ones that can be showstoppers.


14-06-2010, 09:09 PM
Im definately going to have a go, thats for sure. I would be lying however if I didnt say I am thinking to myself quietly "jeez, will this even work" ha ha.
The table has been ordered and I am just waiting to hear back from the designer regarding changing the pulleys, after that Ill be waiting a week or so for the parts before I steam into it.

Im in Cardiff if anyone local fancies giving me a hand ha ha..................no serious that's Cardiff, you know, the ones who got beat by Blackpool in the play-offs, grrrrrrr!!

14-06-2010, 10:30 PM
Have a search round the site, there were a couple of threads on open ended belt drive, including some discussion on how to improve the backlash in the belt. I think at least one other member was doing this. The othe way for a router of this size is roller-chain as used by the Blacktoe 8x4 design

15-06-2010, 04:11 PM

Im definately making some headway on the use of the belts, I was looking at the chain option but I would prefer to try the belt setup first. I like the blacktoe, shame its so expensive for the amount of parts used to make it. Shipping is charged at $650 too, the designer does refund the difference once he gets the final cost from the courier, thats what he told me anyway.