Are my stainless steel tube tolerances problematic?


I’ve bought 25.4 mm stainless steel tube at a local hardware store and cleaned it with acetone. When I slide the printed foot over it it’s snug in some places but loose in others. The tube diameter varies over its length between 25.5 and 25.8 mm! How much of a problem is that? I guess the elasticity of the printed parts might compensate some tolerance of the steel but that was not the idea, right?

In Tom’s build I’ve seen him give the gantry a push and it rolled pretty freely - but precision was not his concern and he didn’t tighten the system much. Is that how your builds behaved before you installed the belts? I imagine that if I tighten the rollers to the point where they don’t wobble on the thinner parts of the tube they will get stuck on the wider parts!

My hardware store guy said that if I wanted higher precision I could go with aluminum. I’m not sure if the steel/aluminum fricion is problematic, or perhaps other properties?

This was a bad surprise for me, I thought stainless steel tube was considered an upgrade.

All the best, Till

After reading more in the forum I rolled my 48" ss tube over a flat surface and found one end sticking up by ~1-2 mm when held flat on the other side. I’m super frustrated because I’ve printed 90% of the parts for 25.4 mm and it seems I should have just gone with standard EMT. Or is that stuff just as bad?


Those tolerances are pretty bad but I bet for the most part you won’t have any issues. Of course this all depends on what you are making, signs, no issues, Giant PCB with a v bit…could be trouble.

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I have a similar issue, I’m able to source 1" 14 gauge stainless steel at a local supplier at a good price.
I took a 16" sample and when measuring the OD with my “cheapish” amazon caliper, it has a variance of -0.20 to + 0.30 mm along the diameter and also its length.
I also put it against my veritas straight edge and there is a gap of 0.063 mm.

How are you fairing out with your MPCNC, so far?

I ended up buying the tubes again, online. The MPCNC is assembled and tested with a pencil. It’s working well, but I was too clever trying to make the bed replaceable and now it’s uneven (had to make a table as well and it was an 80% success only). I’ve since started working full-time and my hobbies are on hold for now.

Thanks for the quick reply Till.
So the tubes you bought the second time around were consistent?