Inventables Community Forum

Procedure to Set Belt Tension

I’m finishing up the assembly of my X-Carve, and have no idea what kind of tension I should have on the belts. I picked up a little fish scale on Amazon and made the following procedure:

  1. On belt of concern, run the carriage or gantry all the way to the “secure” side of the belt (the non-adjusting end).
  2. Zero scale/tension gauge and hook under belt in middle of belt.
  3. With one hand holding a small ruler, pull up with the scale until the belt has been pulled up to the 1 inch mark, then read the gauge.

Right now, I have my belts all set so it takes 6 pounds of force to pull them up one inch. When I move the carriage or gantry by hand it seems to take a little force, but I’m not sure how easy they should be to move by hand. I also rechecked them 24 hours later and they were still pretty much 6 pounds, so they don’t seem to have been stretched too much.

Has anyone else done something similar to this for an X-Carve that is properly tensioned? Is 6 pounds too much tension for 1 inch of deflection?

For those interested, the scale is a [Mango Spot Digital Fishing Hook Hanging Scale][1]. It’s currently on sale for $7.99 on Amazon.

@PaulKaplan, this may be something your engineers could easily check and make into a tensioning procedure, once they verify what the proper tension should be.



I am no engineer but the tension on the belts X,Y are dependent on the work you do most of us had problems and we learn; after all the machine is assembled by every one of us. I was engraving on the reverse side of a mirror as it is glass the work executed like a dream, but when I tried on hard wood it revealed that there were double line etc. I had to increase the tension on belts, increased pot etc. The following are few issues and these are due to purely my lack of knowledge.
The y axis was not square
The z axis was not perpendicular
My grub screws were loose and the stepper motors slipping
The eccentric nuts got loose and fell off
The belt slipped in spite of heat shrinking had do it again.
And I learnt more issues from the forum and corrected issues.
I am sort of addicted to the forum and it is a good learning place I visit on a daily basis.
So the bottom line is there are a lot of things go wrong during assembly in spite of excellent videos and detailed description. When you watch the videos again it all make sense where we go wrong.
My machine is working well now and the customer support at inventables is extraordinary considering they are supplying all over the world.
Hope this makes sense.


Great minds :smile:

I ended up going back and doing a tutorial video that wasn’t reliant on the scale. I found that if you undo the adjustable bolt at the end of your belt, and tension the belt so that it just barely touches the endplate, then use a tool to push the bolt through and put the nut on it, that seemed to give you proper tension.

Give your belts a few days (or a few runs on the machine) and I’m certain that they’ll need to be tightened up. I was seeing about 2.8 pounds at .5 inches, so ~6 pounds at 1 inch sounds reasonable.


I just got through maybe the third hour of cutting, mostly in the lower left quadrant, and the left Y belt broke. Looks like time to send Help@ an e-mail to get some new belt, but also a good time to drop tension to 5 pounds at 1 inch and see how that works.

Also make sure that your pulleys are well aligned, I seem to remember another person on the forum going through several belts and thinking it was a tension issue, and it turns out that it was rubbing on the side of a pulley/idler and wearing out there.


That’s a good point. I’ve been watching them to make sure the belt was centered in the pulley and the idler wheels, but that’s something I can mention in the calibration video I’m working on.

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That’s a good idea, something that could probably have the parts made completely by the X-Carve (excepting hardware).

Just a quick video of the belt tension jig i built on the X- Carve. Just some other ideas for a fun project and a great tool to use with your X-Carve.


That, sir, is brilliant! You should make it a project for Inventables.

@Zach_Kaplan A project for this is worth a gift card, in my opinion. It’ll help solve a BUNCH of maintenance issues…

That is great! What did you end up using as a tensioning spring?

And as cool and informative as the video was, if you add a little more light in your future videos, even with just a clamping shop light, it will both help with the auto focus, and make it easier to see on either Y side. But overall the content was awsome.

The spring was something i had in my shop no idea what it came out of or where it came from. Thanks for the pointers that was my first ever video. I plan to make some more though and i’ll definitely remember the lights.

Thanks Robert.

The jig is very quick and easy to use. I use it when I start up my machine every time as part of the maintenance checks. Takes about 2 minutes to check all your belts.

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That is brilliant, Wade! Best youtube view over morning coffee in weeks.

Looking forward to another view of the tension jig.

…I want one of those. :smile:

Hey @RobertA_Rieke you said you were still trying to sort out your belt tension, what have you found to work for you lately? I went and got myself a fish scale, although it’s a dial style (I didn’t want to spend $40 on a digital one at my local shops). I’m not sure if the dial ones are a bit tougher, but I had gotten my tension to about 2lbs at 1 in (about 5lbs at 1.5") and that seems very tight, am I just being overly cautious?

With the 24V spindle, it was working fine for me at 3.5 pounds at 1 inch. I just installed the 611 though, and, theoretically, I may have to dial up the tension a little to account for the increased router weight. My 3/4" wasteboard cutter test cuts seemed to work just fine though, so I’m going to stick with 3.5#/1" until I see an actual problem.

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Awesome, thanks! I just got my Makita installed and was having some misaligned cuts, adjusted my pots and was going to tackle the belts next! I might need to purchase one of those cheap digital scales online.

Now I’m thinking I need to be a little more accurate on my belt tensions. Never had a problem. Haven’t even had to re-tighten them, but now you’re scaring me that I’ve got them adjusted all wrong. Have know idea how tight they are. Just made them tight. So I think I’m going to take your advise and order one of these. Goes to 11# and by .01. Thanks for the scare. Oh, thats right…it’s Halloween!

If it’s not broken, I wouldn’t fix it. It’s a great thing to have available though, and if you haven’t had any problems I’d like to know what your belts are set at.

Like I said Robert. I don’t know what I set them at. Just tightened them till I felt it was right. What ever that might be. When I get the scale, I’ll let you know.
BTW, I am running 23’s and 611 if that matters.

I just put the 611 on today (and have 23’s), and I just cut some aluminum T6061 from Inventables using the same belt tension. Just a little feed/speed testing, but tomorrow I cut Y-axis supports. Once I get them cut and am 100% positive on the feed/speeds, I’ll put them up with the project.