[Analias]

I have a CRP-4848 that I am nearing completion on. One aspect of construction that I completely forgotten to consider is surfacing the table. I have 64"x52" area I would like to surface. The thickness would depend on the work hold solution. I would like to include some integrated work holding for clamps, blocks, vices, and even custom fixtures. I would like to be able to work with wood, plastics, foam, and aluminum. A precision surface would be nice.

I have considered wood, aluminum/steel, glass, and granite. I would expect wood to suffer the most from moisture, expansion, and marking too easily. The prices I have seen for aluminum/steel have been upwards to $1100. Although industrial glass has been suggested, I would also expect it be easily marked by a wayward tool. Granite so far seems to be the cheapest (~$5 sqft) when looking at local suppliers, but I'm curious about surface tolerances, cut fees, and most pieces I have seen only have the top surface cut to tolerance.

What are some of the solutions folks here have come up with? I would be very interested in opinions and actual solutions people have used.

[adprinter]

What I did on my table is to construct a frame out of 1/4" thick 2"x2" angle steel, with 1" square tube steel cross supports with 1/4" thick flat stock shims/support under the 1" square tubes. For the table surface, I mounted 3/4"x3.5" T6061 aluminum slats to the 1" square steel tubes. These slats are arranged to run the length of the table (48"), and are spaced 5/8" apart. This allows for 1/2" bolts to be inserted into the "Slots" between the slats. I mounted a ball bearing assembly to each end of 1/4" thich flat stock steel bars. These bearings ride against the upper surface of the outer edge of the steel angle stock of the table's frame (I.E. the "Lip" created by the horizontal plane of the 2" angle steel, left over by the 1" square tube which is mounted against the vertical plane of the 2" angle steel). The bearing mounts were designed to raise the flat steel bars to within 0.040" from the lower surface of the 3/4" aluminum slats of the table's surface. The flat stock bars were drilled and tapped to accept 1/2" 13TPI bolts inserted between the aluminum slats of the table's surface. This design allows for an almost infinite range of mounting positions along the table's length, and provides a sturdy surface to mount work pieces to the table. I work with 1.25" thick laminated Oak (recycled tractor-trailer flooring) most of the time, and this system allows me to really wrench the work piece down flat against the table's surface (to overcome warpage of the wood). This design has served me well for the past 5 years. My initial thoughts were that it would be necessary to plane the table's surface, after construction in order to make it perfectly flat. However, experience has now taught me, that as long as the table's surface is fairly "CLOSE to flat" it is not all that critical. Since you will RARELY ever find a work piece that is perfectly flat anyway! (I.E. for surface-critical work such as engraving very small text characters, the first step in preparation is to plane the surface to be engraved using a flat end mill). The point is: even if you have a polished cast-iron surface as your table, the work material will almost NEVER be flat enough to perform precision work such as engravings without the need to first plane it flat!

[TLHarrell]

MDF spoilboard is one of the more cost effective ways to go. Set up braces under the table to hold it on. Cut a piece of 3/4" MDF (see if your local supplier can get you the low density type) and secure it to the frame below. (Countersink screw heads below the surface, or screw up from below) Flycut the surface so it's flat and in plane with your X-Y axis. For most cutting operations, you can simply screw clamps directly to it, or use a program to spot drill some hold down points in scrap areas.

[coherent]

I currently have MDF and must admit it's cheap and sacrificial. I was considering a complete bed made from aluminum T--slot panel but the price for anything in the size I needed eliminated that option quickly. I came across a few posts where folks are using slatwall. I've ordered a couple of samples from here Slatwall Systems - Panels, Hooks and Organizers , but haven't received them or tried the stuff for this purpose so can't comment.
If anyone who has used this stuff for a cnc router bed can provide their thoughts on it's use and suitability for t-slot clamping work securely, I'm sure folks would be curious.

[maxkauker]

That Slatwall looks promising. Under the "Loads" section apparently it can take up to a 25lbs load 6" form the surface. That's more than enough for basic CNC operations. I'm curious as to how thick it is though. Though it can supposedly handle 25lbs, it may flex under that load. Please post back here when you receive it. I am getting fed up with a MDF top especially when I cut aluminum that requires coolant.

[coherent]

Well I got the samples, and they are just little squares of the thin metal surface options. What I wanted was a slice of the actual material. It looks like it's made of MDF and surfaced with the metal. Can't see how the slots are finished. They sell metal channels to slide in the slots to strengthen them 3 time the standard. I'm sure it would work for wood or other dry cutting. Prob not with liquid coolants.