[Mountaincraft]

I've been planning my first CNC build for some time...

My first of at least three builds is to be a 'heavily' beefed up version of a solsylva 2' x 4' rack and pinion table.. It will be 'at least' a 4' x 8' table, and use NEMA 34 steppers..

My first order of business is to build the x (and y) rails...

The plans call for a 3/4 inch black pipe to be used for these rails, constructed by drilling holes and then fishing 3/8" nuts inside of them and threading 3/8" rod into them, tightening nuts against them on the outside and then grinding away any out of round caused by this method...

I want to use 1" cold rolled round bar stock instead... This will increase mass, and allow me to either drill and tap holes for the 3/8" rod, drill and weld threaded rod into the holes, or to use inserts...

So I wanted to discuss the pro and cons of each method, and the how to of each method..

Drilling and tapping... I have only tapped holes that were drilled all the way through a piece of material.. never one that is drilled 'partially' through the material... Is a special tap and or technique needed for this situation, or is a standard tap and drill used?

Welding.. this approach allows me to be a little more sloppy in the drilling and alignment of the holes, as I can rough assemble the whole rail, and then align it, and tack weld it into position.. however, there is risk of warping of the stock from welding when I perm weld the rods.., and there is also the inability to replace worn or stripped rod later..

inserts.. I have never used them, nor know anything about them..

Besides the merits of each method, I'd be interested in hearing suggestions as to what is the best way to go about aligning and drilling the holes... It's not a simple thing in my mind to just snap a line on a piece of bar stock or pipe and expect that it will be perfectly parallel to the length of the pipe (ie not wrap around it at all).. especially a problem when it comes to drilling the holes so that they remain perfectly parallel to each other (perpendicular to the pipe)..

I have an idea of how to approach this by making several wooden drilling blocks to hold the pipe as I drill it in the drill press.. but I'd really like to hear from those who do this sort of job on a regular basis, and how they would approach it..

I'm going down to buy the bar stock tomorrow and I'll start a build thread once I set a drill to it...

Thanks for your time...
Mark

[Mountaincraft]

Also, what is the hot ticket in as far as drill bits for this, so that I'm not sitting there forever watching smoke come off of the bit as I burn one up on every hole?
:drowning: