Why 9mm timing belts?

I have to ask. Why 9mm timing belts instead of 10mm?

I’m upgrading atleast one motor on mine and bought some 10mm pulleys and I’m tempted to upgrade them all and go to 10mm belts as they seem
Easier to get from a USA shipper

Because the pulleys are 10mm and the wider belts would rub?

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I’m more asking why carbide settled on a 9mm belt instead of a 10mm belt which seem easier to get.

@WillAdams actually answered your question. A 9mm belt has some wiggle room on a 10mm pulley. A 10mm belt on a 10mm pulley has to be 100% aligned properly or it will rub and wear out.

The pulleys already overhang the ends of the stepper motor shafts (the lengths of which were set when the launch edition machines had 6mm belts and matching pulleys) — perhaps the increase to greater than 10mm pulleys (to fit 10mm belts) was a bridge too far?

Also 9mm is a Gates standard size for the GT2 belts which come in 3, 6 and 9mm from the OEM. The 10mm and 15mm belt sizes seem to be later additions from the clone makers.


Ok thanks. Was just curious. As I see more steel core 10mm belts than 9mm.

I did not know that 9mm was the oem size

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You’re not missing very much on 9mm vs 10mm, changing core material has more effect -


I’m more concerned with easily available and fast shipping of replacement belts than I am in increasing strength. My stepper motors are not as strong as the belts.

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The OEM Gates belts are good but expensive.

The reprap.nl kevlar cored belts worked very well for me and don’t fail as abruptly as the steel core belts. I really abused mine and they just kept on going.

You could just buy a big roll of the steel stuff from Powge transmission parts store on AliExpress and have plenty to spare to replace it every 6 months before it fails. (I believe that’s VinceFab’s approach)

If you use the phone app trick to measure tension you’ll be able to spot the belt cores packing up when the machine loses tone & tension.


What is this phone app trick?

I currently buy my belts in bulk rolls from Ali express just hate dealing with the shipping from China with some of the problems I’ve had through AliExpress. . I replace them every 2-3 months because I run them hard and two belt changes are still cheaper than 1 broken bit and the unscheduled down time that is caused by a broken belts.

Gates has a frequency measuring app for their pushbike toothed belts which works on our Shapeoko belts too

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Wow. Maybe I’ve been doing it wrong.

turns out my belts have not been tight enough so I got that fixed, will have to recalibrate tomorrow night

I replaced by x axis stepper motor with a stronger one that was recommended makes a huge difference the x axis holds its position significantly stronger than the y now. I used to be able to push the x with 2 fingers when powered up, now I can nearly put my body weight into it. and the new motor is nearly silent when moving which I thought was weird

On a side not the 10mm pulleys I ordered off amazon are 10.8 mm wide between the flanges, the stock ones are significantly smaller than 9 mm at 7.6mm.


The narrower stock pulleys are either from a launch edition machine or Z-axis pulleys got mixed up onto X and Y — if the latter let us know at support@carbide3d.com

Actually now that I think about it it was an old z axis pulley that I pulled off when I did the hdz upgrade. I did not think that it would be different but it makes sense. Ok measure the one off the ceiling motor when I get home.

ETA. Now that I think about it how did I not catch that last night.

Interesting, which stepper did you use for the replacement?

STEPPERONLINE Low Current Nema 23… https://www.amazon.com/dp/B00PNEPKH6?ref=ppx_pop_mob_ap_share

WINSINN GT2 Pulley 20 Teeth 8mm… https://www.amazon.com/dp/B07BTDRW5Z?ref=ppx_pop_mob_ap_share

Bolt on other than it does not come with a connector. I need to sit down and source some connectors. For now I cut the connector off the old one with plenty of wire to spare.

For the price I’m seriously considering replacing all the other steppers and buying a 4th for a spare. I’ve got the pulleys after all. Just need to get it past my cfo( wife) who already replied with “is this something you need”. I guess telling her it depends on her definition of need.


The wire colors even match up

Thank you for the stepper motor link. I was shopping around for such a drop in replacement.