I was thinking I might build a small wooden table...make the main beams out of laminated plywood. Table would rout 5 x 3 or 4 feet. I could use the MM till I get the 5 x 12 table done.

My laser kit has been examined and all of the pieces for the Y car fit nicely together. I need to find a flat platform to mount it onto for welding. The spider has 6 hole locations which is what I wanted.

So do I begin my own build thread or does this introductory thread become it ?

I will soon start posting pictures (I need a refresher course in resizing first)

This becomes your thread. I will move it once you start.

Now it is time to start looking for deals on steel. I will consider clean salvage if not twisted or bowed.... otherwise I think I will bundle a material list and let the local suppliers quote against each other.

But I prefer a mixture of salvage and new steel on more critical components.

My X beams are for a 5 foot cutting width so do I need to worry about flex with the longer beams. I have read the other threads on this topic. Some have used 1/4 inch (which might be a bit too much overkill) and others have used 3/16 inch instead of the 1/8 which is the minimal requirement. I am using 600 in oz motors with 1:3 belt reduction. I think I will use 3/16 steel so I can eliminate a clamp strip.

Sounding serious.
Another build on the horizon.

When I reduced the height of the rails to 30mm prior to grinding the v section,
I used the strip for my clamping strip.

3/16 wall box will give you more mass and inertia for your motors to deal with.
Just something to think about (along with everything else):)

I have 3/16" wall gantry tubes with a 5' cutting width.
I think I built a pretty robust machine, but to lean on it and feel it shake during rapid direction changes, I wonder how it would be with an 1//8" wall instead.

I am considering using hardened V caps but the additional cost for a 5 x 12 machine is significant and I might rather use the money to purchase a nice quiet running spindle. I realize I could experience some uneven track wear but you to some extent compensate for that when you resurface your spoil board
..... also I am assuming that there is tolerance to allow you to regrind your MM rails should you experience uneven wear.

I am selling 13 acres of ground and when I have cash in hand I am going to lay aside all other projects and get this MM done ... until then I will build the Y car and gantry. A 5 x 12 table is going to take more time and cash. I also need to reserve some $$$ because I have other cnc projects and some remodeling in the building where I will eventually operate the MM.

Rapid,
Adding the hardened rails later is not unbearable as long as the Mechmate is not a machine you have based production needs on and a little planning is done for the upgrade in the future. It adds a bit of complexity to add them later because your gantry spacing is set. Your overhang will be a constant that needs to be maintained for the rack. Not that it cannot be done but it is a bit more challenging. Usually the V-rail is bolted on to the side of the angle. This would move your wheel space by the thickness of the lip cut away dimension. I understand the money situation and I am only trying to give you information for you to work with.

It is the profile of the tubing that makes gantry tubes rigid not the thickness. It will add to it, yes, but not as much as you would think. It is like over-engineering for no good reason. If it was round and not rectangular, it would be different. The complexity of the layers and assembly add strength also; so the 2mm suggested thickness is sufficient and is 0.040" less than 0.125" tubing so the strength is already gained. Adding too much weight will add wear to other components as well and increases the load that the steppers have to move. This may result in lost steps at a higher feed rate. My 2 cents.

I understand that.
My post probably could have been clearer.
My reasoning to use 3/16"s was to eliminate the clamp strip, as was mentioned in post #43 by Rapid.
I posted my thoughts about the added weight merely as food for thought, IE a lighter gantry would change directions easier.

Sorry, I missed that Darren

...I used 3/16" wall tube too so I could tap everything and eliminate the clamp strip.
I was using 7.2 geared motors too....the extra mass wasn't that significant for my set up.

FYI... I have 4:1 belt drives.