[MajorTendonitis]

It's actually been done on a few builds here, though I suppose many that build here with t-slot, in practice, see deviations in flatness less than .005" which would be good enough for most stock linear rail, under the loads put on them in the "DIY" world....

I guess the next question would be if the gear rack was wide enough also , as it's not as wide as 25mm linear rail is it?
I notice they sell gear rack in straight cut and helical cut teeth , but always see straight cut teeth in builds ?

[ger21]

Helical is better, but.

You need to keep the pinion from moving axially. This is typically done by mounting it to a gearbox that keeps it from moving. Without a gearbox, you'll need to make a custom belt reduction using thrust bearings on the pinion.

And, until recently, inexpensive helical rack and pinion didn't exist.

[Uguessedit]

Not a big fan of extruded aluminum unless it’s for a homemade enclosure. My original router I had ripped it all apart and machined the frame for a solid base linear model that is very rigid. Then again I cut aluminum with it and use it for a backup to my industrial machines for projects not as intricate. I recently rebuilt it and have a 1” thick aluminum spoil board with pins and toe clamps. I also chose servos and won’t look back with 400 rapids it’s a nice time saver from the conventional 20x40 size. Someday I’m sure I will build a full table but for now I’ve got everything one needs to make a vast majority of components. Attached is a photo of the new frame. Given ideas it’s probably expensive for most to use bar stock and machine to precision and mounting for anything that’s decent sized or has legs.

Well my concern is , working with a steel gantry would most likely be a pita for me . I'm not trying to take the easy way out , just trying to be realistic.
I have big drill press and can make a jig to make sure all my holes are lines up properly, but I'm not sure about the rest , like would the holes be strong enough after I tapped them out etc .
After I look at Probotix's cnc design , I'm sure a piece of 3060 is going to be 10 times more rigid then there system .