Mounting A Mill

[Chris H]

I've seen some various threads on installing and mounting mills into a shop and am curious about the trade-offs of the various ways.

What do you actually gain by fixed mounting, that is, screwing the machine base to a solid concrete floor, that you would lose by putting it on a fully mobile stand? I'm assuming it's simply a rigidity issue, but at what point (speeds and materials) does that come into play? For instance, if the mill was trying to take a big cut on a hard metal versus a smaller cut on a softer metal? What about the physical size of the cutter itself? I would imagine that a small 1/4" cutter would shake the machine less than a 3" cutter would, so where is the approximate limit? The machines I'm looking at are the Charter Oak CNC mill (I think the 12Z model mill?) and the PM 935.

The ratcheting casters that Coolidge posted look very interesting, too, as a practical in between measure. I just don't know how to evaluate what 'practical' is yet.

 

[T Bredehoft]

I didn't have room for a freestanding (wheeled or not) mill, so I put my PM25 on a counter (retired Formica kitchen type), reinforced it underneath with double thickness of 3/4 plywood and an additional back to front 2 X 4 on each side. For what I do its' solid as a rock. The largest cutter I have is 1 1/2 face mill. It sings along nicely in aluminum, makes a little heavier weather in steel. I've heard that 2 1/2 is max for a face mill on this machine. Your PM935 should handle the 3" with no problems.

 

[hman]

I looked at the PM935. That's a pretty large mill, and probably as top-heavy as other knee mills.

I would be very hesitant to put casters under something this big! Probably not necessary to bolt it to the floor (you're not in earthquake country, are you?) As long as all four corners of the base sit flat on the concrete, the sheer weight of the mill will keep it from shaking.

I've heard that the folks at PM (machinetoolsonline.com) are very helpful, so you might want to give them a call and ask their advice.

 

[coffmajt]

I used the rubber feet machine mounts under my knee mill and have been real happy. Does not shake while using a 2.5 inch face mill and the bed has stayed level for the past 4 years without needing adjustments.