10mm vs 6mm belt

I accidentally wound up buying the pulleys, idlers, and belt in 6mm rather than the suggested 10mm width. This is my first MPCNC build, and I am going for a 24x24" size. I have the option of returning the parts and getting 10mm width versions, but that is going to cost me about $16 more ($23 for what I have, $39 for the 10mm) and set my build back by about a week waiting on the new deliveries. I plan to build this as a vinyl cutter initially, and maybe try out adding a router at a later time, so if the 6mm is definitely fine for the vinyl and probably fine for the router, I would rather keep what I have and keep the progress going on the build while I have some time off work for the holidays. Unless someone has a good reason for me to order the new stuff immediately and return the old?

We used 6mm belts all the way up through burley with no problem. I think you’re definitely on for vinyl, and probably ok for the router. I’d plan on spending it at some point because you WILL want to push it at some point, but I totally understand wanting to get the machine together right NOW.

TL;DR Thanks for the reply, duly noted 6mm is “ok not great”, but I went ahead and ordered the correct parts anyway!

Full version:
I spent the evening going back and forth over what to do, and I ended up going ahead and ordering the 10mm hardware. The biggest reason was that, as I was looking at the trucks, I realized that the spacing for the idlers (as well as the drive gear, but that is mounted to the shaft of the stepper so less concern there) is designed specifically for the 10mm width, and using my hardware would’ve left a good bit of “play” for the idlers to move up and down on the mounting bolts since they were narrower. I was going to just print some spacers, but designing mods for something I haven’t even built yet just didn’t feel right. I still have at least half the parts to print, and the rest of my mounting hardware (the 5mm nuts and bolts) won’t be here til the 23rd anyway, so I figured its probably worth just doing it right the first time. If it had been just the belt that was 6mm (or even the drive pulleys too) I probably would not have worried about it, but it was really the idlers that were bothering me, and if I have to wait for one set of new parts, the other parts don’t make the wait any longer…

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I probably wouldn’t worry about the 6mm belt too much, but one thing that I would not do is build intending to change it later.

The one thing that I noted with my Primo build is that it’s going to be trouble if I ever want to remove the belt holders from the corners in the future. They were quite tight when being installed, and I’m almost sure that the only way they’re ever coming out is with either the corner or the belt holder in pieces.

This is actually a good thing for the initial build, IMO, but not such a great thing for taking it apart and rebuilding later. It likely is possible to take those belt holders out, if you do it just right, but I’m not confident that the parts will survive, and would plan on having replacements ready, just in case.

Spacers on the idlers would certainly do the trick, you would just need to be sure that you lined them up to the same direction that you put the belts on the holders.

In any case, I’m sure that you’ll be happier with the 10mm belt.

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Afaik you can not use 6mm idlers and pulleys. Belt is okayish.

I’d kind of expect the belt to keep the idlers in line, but I know Ryan recommends the 10mm idlers even with the 6mm belts because 1)they fit the trucks and 2)apparently they tend to have better bearings.
Either way, since this isn’t the thing holding you up, I think you’ll feel a lot better about having the bigger belt, especially later.
Speaking of bigger belts later, now that I’m in my forties, I find my old belts have to be upsized, too.