I am building a fixed gantry CNC foam-cutting mill. It will only be cutting foam.

Usable "X" is 30 inches, so drill rod length will be 60 inches.

What is the recommended diameter for the drill rod in this application?

Thank you.

Rgds,
G. R.

The bigger the dia the better on 60" I'm thinking 1/2-3/4" dia.

where are you going to get 60" long drill rod?

Phil

A drill rod in 60" will be hard to find.

IS that 60" one rod? and how is that supported? How accurate do you want this to be? What sort of weight will they carry?

FYI
A 60" 1/2" drill rod 'fixed' mounting at either end with a 10lb load at 30" will deflect ~0.13"
A 60" 3/4 drill rod 'fixed' mounting at either end with a 10lb load at 30" will deflect ~0.026"

For simple support at both ends those figures become 1/2" = ~0.52" deflection, 3/4" ~0.1" deflection.

For a *really* rough estimate within a small margin if you double the weight the deflection would double too.


note for a home built machine the actual rigidity of end supports would be somewhere between 'fixed' and 'simple'. 'Fixed' meaning absolutely no movement, not feasible unless the machine is really massive. The much used idea of adjustment blocks with four bolts around the shaft would be more or less equivalent to a 'simple' support.

Thanks for the suggestions.

As to the source of drill rod, how about

http://www.crucibleservice.com/eselector/prodbyapp/special/drillrod.html

As you can see, they have it in 3 foot and 12 foot lengths. Am I missing something here or is there really no problem about sources?

Once again, thanks a lot.

Rgds,
G.R.

Use 3/4 rod with open style bearing and support the entire length.Thats what I did and it seems to work fine.Fixed gantry is the way to go because you can make it more rigid.Good luck!

I'd recommend chrome plated shafting for rails. There's nothing special about drill rod in the annealed state (which it is when puchased). Chrome plate is much harder, so long as you treat it nice without nicking it. Friction is also much reduced.