Poll: How big is your x-gantry v-rail?

I am interested to know the size of your x-gantry v-rails.

My x-gantry v-rail measures 107.3mm from vwheel edge to vwheel edge.
What size are yours?

Thanks to the excellent assembly manual, I was able to build my Longmill(V3) in less than a week in my spare time.

But… I had a number of problems getting it calibrated for accuracy: my v-rails on my y-axis were small, the vwheels measured 19.3mm, so the vwheels couldnt tighten up enough. Tech support sent me new vwheels promptly, and replacement v-rails when that didnt solve the problem. Tech support was excellent.

With everything tightened up, I noticed a problem with the x-gantry v-rail: accuracy problems and a “bow” in the rail itself. After measuring, tech support sent me a replacement v-rail and a set of “fat” vwheels (measuring 20.5mm inside diameter).

(Thanks so much to Kelly & Patrik for their help!)

Now, less than a month later, I had to tighten the eccentric nuts on the x-gantry up to its tightest setting. The next time will require vwheel replacement. I have only done about 10 small (approx 100-160mm square) carves with it, as I am still testing and learning feeds & speeds. It seems to me to be too soon to be at this point already. 10 small carves and the v-wheels are already worn to near replacement? Is this normal for everyone?

My x-gantry v-rail measures 107.3mm from vwheel edge to vwheel edge.

What size are yours?

I appreciate your input greatly. Thanks in advance for taking the time.

@Markus Assuming that I measured it correctly, mine is 106.43mm.

Thanks Grant. I wonder if the wear is consistent with mine? I wonder if Ive overtightened, but the vwheels on the bottom can almost spin freely.

@Markus I’ve had no wear that is noticeable. I’m sure that there is wear, but it 's not an issue. If the bottom wheels spin freely, you are not over tightened - just the opposite. As you’re read already, the top wheels need to be somewhat difficult to turn with your fingers. This is not an exact science, clearly. I’ve found that, when adjusting all the wheels, some pressure on the bottom of the gantry helps to get things properly adjusted. That is, I take the weight of the gantry off the top wheels when I adjust them. Otherwise the shear weight of the gantry makes it seem like the wheels are tight, when they really aren’t.

Weird… My eccentric nuts are tightened right up, theres nowhere to go anymore.

@Markus It is strange and I really don’t have anything to add. It looks like my rail is smaller than yours by a very small amount. So, that is not the issue. I find it hard to believe that wear is the issue, but nothing is impossible. I’ve had my Mill for almost a year, and others here have had theirs longer and are likely using them more than I do.
I’m sure that the Sienci guys will get to the bottom of this. When all is well, please report back so that, should this come up with someone else, we’ll have a idea on how to proceed.
Good luck.

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