3GT2 belting keeps breaking

For cutting wood on my GT2 9mm belting-269 oz/in steppers…I use 500 IPM rapids…roughing up to 350 IPM in soft woods and 150 to 250 for hard woods.

For pocketing with a 1/4" bit with a low stepover (8%) and a ramped toolpath into the pocket, I am able to easily cut 1/2" depth of cut with a 1/4" bit in both hard and soft wood. You must have proper toolpaths to do this…

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What are your acceleration settings?

I’ll post them when I get home from work, bear in mind I am no longer using grbl I am running the Gecko G540 and Mach3.

The belt clips are 12mm wide total but the slot is only 7mm wide. You could try to expand the slots by 1.5 mm on each side to fit the 9mm belts and some play. It’d only leave 1mm on each side of the clip but the clips are made from 1.5mm cold rolled steel.

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I actually did this when I upgraded to 9mm GT2 belting. I don’t know if it will hold forever but it is still going strong after 10+ months. On one of the 4 it had a slightly jagged edge and it started to fray the belt there (go figure). After smoothing it out, it’s fine now. I used a Dremel to enlarge the slots.

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Is this everything needed for belt upgrades?

ok I figured I would get a list together for when I eventually snapped the stock belts. First I want to lift it inch or so so I can add t slots directly to the wasteboard if I can find plates the Triquetra plates are out of stock

Not to take anything away from Charlie and his taller endplates and his zeroing plate, but you could just make your own on the x-carve.


Hey I was reading those lol

This particular ebay store was the only place I could get an 8mm bore 3GT pulley back when I was looking for this.

While belts are history for me as far as tension I did the following till the very end with fantastic results for such a huge machine. The logic in what I used to do should apply to any type of a belt.

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Looks like a 5x11mm bearing, this one has a dynamic load number of 403 Newton, the MakerslideIdler wheel bearings are 5x16 with a dynamic load bearing of 1430 Newton.

Just try them out and see what happens. If the bearings fail you can always replace them with two 5x16 flanged bearings ike the SO3 does although they go even bigger. (F624ZZ)

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Sorry, the reference is for the 4mm shaft diameter, on ebay search for F625ZZ
You might just google in your area, many robot an print shops carry this bearing

Or just assemble a standard bearing, if your machine is properly aligned the belt will never hit the edges anyway

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Larger than what? The 625 2RS are identical to the Inventables bearings in Idler and Makerslide wheels. Idler seems based on the Makerslide Idler but with a center section of 5mm vs 1mm on the original one so they should be wide enough for the 9mm belts.

Rotary CNC? tell us more!

I was using openbuilds ones on my monster and I got to warn you that the collar on them is bit taller than xcarve.
I I had to sand off them a bit on X axis or they were riding on extrusion.

You can kinda see it on my old pic here:

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Go for it!


Yes was just a tinny bit, I was not even sure it first but that I seen them spinning when movie carriage without belts. If I remember right I just put then on a bolt and into a drill and ran them over sanding 3m block and was enough.

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Were those GT3 belts the 1536 loops? How’d it go cutting and trimming for the machine? Any real issues?

I put a long bolt through them and just pressed them against my disk sander. They spun quickly and ground down about a mm on each side very fast. It only took a minute to do them all.

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Have you considered 5/16" width Kevlar reinforced belts?

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