Belt Tension and Eccentric Nuts

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Belt Tension and Eccentric Nuts

Post by goodGuy » Fri Oct 10, 2014 7:17 pm

Shapeoko 2

How tight should the x/y belts be in general? Should I be able to get a finger under it? 2 fingers?

Still reading everything, but any quick advice or links about best method of tightening these eccentric nuts would be appreciated as well. If I tighten them all enough to not freely spin, the y axis becomes stiffer vs the silk smooth freeflowing movement when they have not been tightened at all. Then when I add the belts in and do them tight (1 finger), it becomes fairly stiff. A tad more than I would think they should be.

Anyway, all help appreciated.


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Re: Belt Tension and Eccentric Nuts

Post by edwardrford » Fri Oct 10, 2014 8:44 pm


The belt should be pretty tight. Slipping 1 finger under it should be fine, slipping 2 should be difficult.

Here's what I do on the v-wheels:
1.) Put the carriage with wheels on the rail with the eccentric turned all the way out (so the wheels are not or barely touching the rail)
2.) With your thumb on the rail, put your 4 fingers below the carriage plate and pull up. You should feel some slop
3.) Adjust the wheels a little tighter
4.) Repeat #2 until you don't feel any slop.

For a quick check of the wheels tension against the rail: You should be able to see the wheels roll when you move the carriage by hand, but if you spin the wheels by hand, you'll feel them engage with the rail, but slip.

Clear as mud?

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Re: Belt Tension and Eccentric Nuts

Post by Schruminator » Fri Oct 10, 2014 9:17 pm

I suppose how many finger you can fit under the belt depends on the length of the belt. I know mine are as tight as can be, but as they are 6 feet long, I'd bet you can slip a few fingers under it. My approach is to make the belts as tight as possible (by hand). The extra wear on them is minimal (and belts are cheap), and it leaves less room for 'slop' in the overall machine accuracy.

On the delrin plastic wheels, I adjusted the eccentric nut so I could not spin the wheel with my finger without the wheel engaging and moving the machine. I don't want it too tight (which may increase binding), but I want it tight enough that it cannot spin without engaging/gripping the rail. No slippage basically.
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