Steel Core Belts - where to purchase

I want to upgrade my belts. I noticed that the new maintenance kit comes with the steel core belts. However, I still have my purchased kit from a couple years back that I’ve only used one wheel from. I don’t want to have to purchase the new kit and have double the inventory. Is there an alternative place to purchase steel core belts that will work for the Shapeoko XXL?

The maintenance kit no longer includes the steel core belts. They were found to be prone to premature failure from the tight bend radius of the pulley routing.

The belts are GT2 profile 2mm pitch 9mm wide — Gates-branded fiberglass versions are available from specialty vendors such as BB Man., SDP/SI, Texas Belting, and possibly 3D printer specialty shops such as Filastruder.


Like Will says the steel core belts can be as much as curse as a blessing.

I found the kevlar cored belts to be a good compromise of life vs tension modulus

I have also used AliExpress to buy fiberglass / steel cored belts from Powge Transmission Parts Store in the past and it seems pretty decent. I’ve not abused the Powge belts over enough time to know about durability yet though.


Thanks guys. Ill look into them.

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No consideration of the newer Gates GT3 belts?

They would require new pulleys — that would be a question for @Luke and @edwardrford

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Last time I looked I only found continuous GT3 belts, no open ended. Has that changed?

You have a CNC; it can’t be that hard to design a tool path to convert a continuous belt to open ended.

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I’m just gonna put this here…


Haha, I’d never looked at the length of the loops to conclude you simply buy a big one and cut it.

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My understanding is that GT3 belts are upgrades/updates of Gates’ GT2 belts and are fully compatible with GT2 sprockets and pulleys. I suspect that Gates has better quality and QC than most, if not all, generic manufacturers.


The GT3 is not a straight upgrade, it has a lot more inherent backlash in the tooth profile which you’d want to be careful of, I’m testing that option out at the moment.

As others have pointed out the pulley diameter on the Shapeoko is a problem for both the steel GT2 and GT3 belts, you won’t find a real Gates GT3 pulley in that small a diameter but there are Chinese clones available. I have gone up in pulley size to reduce the bending stress on the belts but that brings other issues…

Edit - might as well add, the Shapeoko pulley is small in order to make best use of the torque of the stepper motors and get small step sizes, if you go to a bigger pulley you have to re-solve that problem some other way. The pulley size is good design for the product.


Has anyone found a good US source for kevlar belts?

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I’m confused - do Shapeokos have Gates GT2 pulleys that aren’t fully compatible with the Gates GT3 belts? :confused:

2001-03-21 Edit: OOPS - I now see that you were talking about steel core belts rather than Gates 2mm pitch GT2 and GT3 fiberglass core belts - Sorry!

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Ah, sorry, naming confusions.

There’s two types of belt (relevant to this), the 2mm pitch 2MGT and the 3mm pitch 3MGT. Gates calles the first version GT2 and later named the new version GT3 because nobody would confuse GT3 with 3MGT, see how different they are?

It gets even worse on AliExpress where half the sellers use the wrong naming too.

So there’s the Gates GT3 belts which don’t seem to have much over the GT2 for tension modulus, I’d still go with the kevlar cored belts from over those. These still have the very tiny backlash even at low tension thanks to the tooth profile and near complete lack of camming action. Gates do this in 3, 6 and 9mm width, the other widths are all third party so far as I know.

There are also 20T GT2 pulleys available from Gates although there are warnings about wear rates for the belt on such tight radius.

Also there are the 3MGT belts with significantly higher tension modulus, a 3mm tooth pitch, more than 10x the backlash (still less than 0.025mm) and available in greater widths. These are substantially thicker than the 2MGT belts and all round stronger. The pulleys for these start larger than the 40mm diameter of the shapeoko pulleys, unless you go AliExpress.


Based on stuff I read on this forum, I went looking for kevlar belts. The only place I found was Reprap, so I ordered from them. Be prepared for a pretty long wait though. Mine took almost 4 weeks to get here.

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Maybe that means that there is only one manufacturer (unfortunately not Gates). But that could be a good thing anyway for predictable/repeatable performance!

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