[maillemaker]

Hi all,

I am considering making a CNC plasma cutter frame and gantry using precision square tubing that bearings can ride along.

Does anyone have a good source for these? McMaster-Carr sells square tubing but I am not sure what to call "precision" square tubing withoutside surfaces sufficient for bearings to run along.

Also, what do you call the bearings that some people use in this application? It looks like they have an eccentric shaft hole that allows the bearing to be adjusted and then locked down. What are these called? Eccentric bearings? What kind of bearing?

Thanks,

Steve

[plain ol Bill]

Can't say I have seen anyone use tubing as the guide for bearings to roll on. Standard structural tubing should have close enough tolerances in the lengths you would be using if you do decide to use it for bearings to roll on. Personally I would do it different but different strokes for different tables.

[BTA PLASMA]

It only exists the moment you set it up. Once it hits a heat cycle your accuracy goes out the window. As long as you can live with that then what you need to do is specify accuracy to the reseller of the tubing. Typically this means youll need to buy a large bundle. You may get lucky by calling your local steel supplier.

[N2950H]

Why wouldn't you just put a piece of CRS or something like that on top of the tubing for the bearings to ride on? That was Precision Plasma's recommendation when building a table for their DIY gantry kit, so that's what I did. Seems to be working great thus far.

[flyinwilly]

I just used regular 2" square CRS tubing for my frame. Once you get your frame welded together, it WILL be slightly out of square, no matter how careful you are. For my guides, I used hardened V rail with V bearings and they work beautifully. With your table leveled, you can place the V rail very precisely on the frame. When you've mounted the Gantry to the rail(s), it will move very smoothly along the rail. The V bearings control both vertical and horizontal movement along the rail. The V rails are accurate to within a few thousandths per foot. Any minor warping will be taken care of by your THC when the machine is running.

I used 2 V bearings for the top mount and 2 regular ball bearings (with an eccentric mount) to ride along the bottom of the rail. My gantry just glides along these rails with little or no friction. It is slightly more expensive to do it this way but I think it is worth the expense.

Good Luck.

Willy