Requirements for Linear Slide Ratings for a mill

[bprzybyl]

Hello all,
you may remember my post the linear motion forum (Carel should at least). I've decided on a mill style 3 axis (future 4th). Maybe even adding that 2 axis job from rannea.com or whatever. Either way-

I found some linear slides by NSK. The brochure says they can support about a ~350 lb max dynamic load. would that be enough? If not, what should I aim for?

The blocks are also 20mm long by 24mm wide. I was thinking spacing them about an inch apart, making them 3" end to end. This would give me up to 8" travel on each axis. If they would be capable of taking the loads of milling, would that amount of spacing be ok?

Then comes another question- Can I cut one linear rail and screw in in tight up to another? I was thinking of taking 4" off the y axis, and give it to the x. This would give me around 12" in the x and 4" in the y. Looking at the model number, it looks like the guy had 2 big rails, and cut them up.

These would be perfect for my application, but if they don't foot the bill for load capacity, then they're a no-no.

Just as a little extra info, I wanna machine mainly aluminum, but would like to have the capability to machine any metal. I really have no need to cut stone. It'd be neat, but not exactly my cup 'o tea.

Thanks all,
Bprzybyl

[pstockley]

How wide are the rails? Another important point to consider is preload. For a milling application they typically use medium to high preload. This helps avoid chatter and generally provides a stiffer platform.

[bprzybyl]

For this model, it says Preload (N), Slight Preload, 0~10; Next column- Rigidity (N/um), Slight preload, 30.

I don't want to sound completely oblivious, but I have no clue as to what those numbers say. I could guess the bearings would move 1 um with 30 N of sideways loading.

The rails are 9mm wide.

Am I still in business for using these?

P.S. - I have decided to use roller screws for linear motion. Saw the idea here, and thought it would be fairly inexpensive. I have access to LARGE engine lates (they need a smiley which has fainted smiling), and they would easily take care of custom threading. I'll just use 2 of them clamped together like ?exlar? does. Basically, I'll do it planetary style. But that's for another post.