Are 20mm Linear Bearings strong enough?

[WarrenW]

Hey Furry, can you tell me where you got the open end linear bearings for the 20mm shafts? How much were they? The machine I'm building is using the roller bearing on pipe concept but for my second machine I'd like to go with your methods.

Thanks!

[furry]

I'm not sure why 36mm shafting is necessary if the shaft is supported and screwed down over it's entire length. Most of the loads applied will be normal to the shaft surface and be distributed to it by 2 or 3 bearing circuits minimum. Essentially in this configuration it's similiar to railing anyway.

Not dismissing your opinion (which is very valid!) but I've seen many commercial machinines using THK railing with very poor underlying supporting structures which flex more than even some unsupported round shaft designs. Which simply goes to say, the design is often more important than the components in some instances.

After saying all that, if you can find me some cheap 6ft THK railing and guides, I'll happily convert my router tomorrow

Warren.. try www.vxb.com and look under linear motion.. not a bad deal on 20mm open bearings with housings.

[WarrenW]

I actually bought my roller bearings from vxb.com and saw their linear shafts there before. So its $40 per 60" shaft and $25/open pillowblock bearing. Thats $90 per side. Not too bad.

One question I have is how did you align the shafts before you mounted them down? Did you just mount one side and then with the gantry on it mount down the other side?

Thanks

Warren

[loves80z]

If U buy hardened drill rod U won't be able to put the holes in it.
If U buy it soft, U should run nylon or something like that on it. The joint could be tricky. I've seen thks butt togather. They abrasive cut the 2 ends to be joined. "Perfectly" square.

[furry]

As you guessed, the shafts were aligned by tightening them down after the finished gantry was sliding on them. Getting it all squared up afterwards only took a few hours by making test cuts in acrylic sheet.

I'll also post some pics of a smaller router I made using unsupported 20mm shafting. I'm still using it to this day as it's extremely precise... perfect for wax models, thin metal sheet and inlays where there isn't a lot of load on the router/spindle.