3XXL - Weaker Alternatives to Z-Axis Springs - Z-Axis skipping


OK - my issue was that whenever my router plunge too quickly, the brushes on my dust shoe would push engage the surface of my material with too much force, and the z-axis would immediately jump up about half an inch, while still continuing the job.

I followed the instructions here - http://www.shapeoko.com/wiki/index.php/Operation_Troubleshooting#Belt_.28SO3.29 - and removed one of the springs (my belt tension was already pretty good). Since then, it’s been working great, but having just the one spring makes me a bit nervous, and I’d rather have two weaker springs than one stronger one. (Please let me know if that’s foolish).

Do you have any recommendations for comparable but weaker springs? A link to McMaster Carr would great, but even the specs for the springs that are included as part of the z-axis build would be awesome.


The springs are a commodity part — you should be able to get weaker replacements at any hardware store.

They were described in the original B.O.M. as:

2.25in to 6.25in Extension Spring

so you should be able to extrapolate from that.

I’m not in front of my XXL, but you should be able to get a rough idea with an extension spring calculator:

Throw some calipers on the stock springs for the requested values and you’re off to the races. Not sure on the material… Stainless steel, maybe?

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As important as length is weight. At 4" extension I bet a single spring on mine was 20 lbs. I couldn’t cut through a piece of 3/4" on top of a piece of 1/4" luan with the router all the way down in the mount. I took one spring off and it still wouldn’t extend far enough, and I’m not fond of pulling off side long term.

Buying locally was a crap shoot, no specs and not many choices. So I went to the McMaster site and found 2 that looked good and ordered them. I put both sets on, both worked fine moving the router manually. I left the second set on as it had a little more retract force, I cut the part I been waiting to make and it worked fine.

9654K195 This is one I left on. It’s a full loop end, I cut it to make it open loop but probably didn’t need to bother.

9433k76 A little weaker than the one above but nearly identical in appearance to the original that was on mine.

I also changed the belt, I figured it had been stretched too many times to have much life left.