The casting tables we use at Elements Concrete were inspired by greatness from a company that most of you may have never heard of (unless youâ€™re a lumberjack on the side). Wood-Mizer is the king of portable sawmills, hands-down. I know this because thatâ€™s what the salesman told me and, more importantly, Iâ€™ve experienced it firsthand. At a rate of 325 board feet per hour, the Wood-Mizer LT40 will cut a 36â€ť diameter log into usable lumber in no time. So, youâ€™re probably wondering, first of all, if this article was published in the correct magazine; and if so, what all this sawmill talk has to do with concrete.
The reality is that the decorative concrete industry is still in its infancy. As a result we often find ourselves using tools and concepts from other established industries and putting them to work for our purpose. As our industry continues to mature we will see the number of products tailored specifically for us grow. In the meantime we might as well learn from the success of others, which is what inspired my best casting table design to date. I call it â€śThe Spine.â€ť
That salesman had pitched to us dozens of features found on a Wood-Mizer, many of which can be found on any sawmill on the market. However, there is one feature on the LT40 that is distinctive both visually and functionally. Wood-Mizer explains the uniqueness of their product this way:
â€śMany people ask us why we chose our unique, cantilevered sawing head for our mills. It wasn’t to make us stand apart visually from other mills – we chose our cantilevered design because it provides you with the most accurate cut in the industry.
Aside from producing the best lumber, a cantilevered head will make your mill weigh less overall which makes your mill truly portable and saves you gas when you’re hauling it from site to site.
Additionally, it will remain level even when your mill is not which is why we say it produces the most accurate cut.
Some people simply don’t understand the technology that goes into the cantilevered design, so they’re quick to assume that a cantilevered head is unstable, unreliable, and produces poor quality lumber. We invite you to join the more than 50,000 customers who discovered for themselves just how accurateÂ Wood-Mizer millsÂ really are.â€ť
The Spine casting table was built on the same principles and concepts as the Wood-Mizer. After building dozens of casting tables over the years, the one crucial element that seemed to elude me every time was how to keep the casting surface flat when the floor was anything but. The reason the Wood-Mizer can cut a perfectly straight board while resting on an uneven, rocky bed of soil is because the cutting head rides on a single rigid I-beam rather than two rails which will inevitably twist. The single most fundamental feature of the Spine table is that it will not twist, bend, or warp. As we all know, concrete will perfectly mimic the surface it is cast upon. If that surface is twisted the finished product will also be twisted. For those of you who have ever shown up to a countertop installation and have attempted to seam two twisted slabs of concrete, the Spine table may be what youâ€™ve been searching for. With some basic tools and minimal welding skills the table can be fully assembled in five hours from start to finish (which is a little faster than it takes to assemble the Lego Imperial Star Destroyer, for those of you with kids). Letâ€™s not forget that it also looks bad ass! Who says all of the cool stuff has to be on top of the casting table? What happened to combining form and function? Although the design is simple enough to build from a single photo, we are going to go through each step and add a few pointers to make your assembly quick and easy.
Itâ€™s always a good idea to gather your parts and tools before beginning, primarily so that when you reach for an item…itâ€™s there. The materials list is as follows:
2â€ťx2â€ťx48â€ť 11 gauge tubular steel (x9) – These are the rails that make the â€śvertebraeâ€ť on the table top.
4â€ťx4â€ťx17 3/8â€ť 11 gauge tubular steel (x4) – These are the table legs which can be adjusted to length as necessary.
4â€ťx4â€ťx40â€ť 11 gauge tubular steel (x2) – These two pieces connect the legs together.
C-Channel â€“ This is the main stabilizer of the table – be sure to check your local steel recycling facility for inexpensive c-channel or I-beams. I have purchased all of my c-channel for $40.00 each by avoiding new material. The size c-channel shown in the photos is C12 with a depth of 12â€ť, width 3.5â€ť, and thickness of 3/8â€ť.
6″ Swivel Caster (x4) – Do not skimp on wheels!
The tools you will need are a welder, a cut-off saw, a magnetic square, and some clamps.
Weld the legs to the cross member using a magnetic square. Be sure to weld a substantial bead to these parts since these joints will be structural and there is no concern for warping on these parts. The legs can be lengthened or shortened to accommodate your preferred working height. I am 6â€™ 4â€ť tall so I prefer a tall casting table, but you should also consider the other people using the tables and what will be comfortable for your employees.
Weld the wheels onto the bottom of the legs and be sure to cover the bearings so hot spatter doesnâ€™t damage them. We typically put two locking casters on opposite corners, which is plenty to keep the table in place when needed.
(Important note on the wheels: The table will only be as good as the wheels it rolls on, and regardless of the weight it should be effortless to roll a table across your shop. I highly recommend the following wheels for this table, which can be purchased from Caster City at www.castercity.com: Polyurethane on Polyolefin Wheel -Model 9, Product Code: 9MG6x2-S.) Of course I had to learn this the hard way: in an effort to save a precious dollar I have used cheaper wheels in the past which nearly cost me thousands in return. I remember casting parts for a large commercial building veneer and quickly running out of shop space. The logical solution was to make the piles of finished product taller instead of wider, which meant a lot of concrete on each table. Iâ€™m not sure exactly how much weight was on this particular table but there came a point where the wheels said “enough is enough.â€ť A slow creak was heard throughout the shop, followed by a loud pop. But it was the sight of all the ball bearings firing at our ankles that clued me in to the pending disaster. Not having learned from a prior incident, I naturally threw my body at the pile of concrete teetering on two wheels. Fortunately, with the help of some quick-thinking employees and some 2x4s, we were able to save ourselves two weeksâ€™ worth of work. The moral of the story â€“ spend the extra five dollars for amazing wheels.
Weld the assembled legs to the c-channel. This can be done easily by working with the table upside-down, simply resting the legs on the bottom of the c-channel and tacking them in place. Attach the assembled legs 22â€ť from the end of the c-channel, and once the legs are secure you can finish the welding with the table right-side up.
This is the part that is typically very difficult and frustrating without a perfectly flat assembly table to build on. However, because we are building around a perfectly flat object as the core of our table, we donâ€™t need a separate assembly surface. What we do need is a simple spacer jig to speed up the assembly of the vertebrae table top. The spacer jig is simply a piece of plywood measuring 48â€ťx9 Âľâ€ť with two rails screwed to the bottom used to ensure even spacing of the 2â€ťx2â€ť steel. (Important note on the 2â€ťx2â€ť steel tube: The orientation of the seams in the 2â€ťx2â€ť steel tube is critical. The side with the factory seam on it is obvious and it should be placed on the side since there is a slight bump. Lay out all nine of the rails with the seams oriented properly as it can be an easy thing to forget.)
Begin working from one end of the table and tack weld the 2â€ťx2â€ť steel tube centered on the c-channel. It is important to not over-weld the 2â€ťx2â€ť steel or warping may occur – six quality tack welds are all that is necessary to hold them to the c-channel. Continue working down the c-channel using the spacer jig to keep your parts square, once youâ€™ve run out of partsâ€¦youâ€™re done.
Aside from acting as a flat casting surface there are many other additional benefits of the Spine table design.
The ability to load and unload tables with a forklift will come in handy since the forks will fit nicely between the rails.
With easy access to the underside of your casting surface itâ€™s easy to remove screws that are attached from the bottom of the mold.
The steel Spine table will last for many years and withstand endless wet polishing.
If you are in need of additional storage space simply add a shelf to the bottom of the table and you have earned 32 square feet of horizontal empty space.
For â€śLâ€ť-shaped countertop pieces simply sister some temporary long 2â€ťx2â€ť steel tube to the existing rails so it only takes up valuable real estate when necessary. This can be done with clamps, or for frequent use consider drilling holes for pins or bolts.
For those of you who are familiar with Google Sketch-Up, the 3-D .skp file can be downloaded here. The Sketch-Up file will allow you to alter the design to fit your needs and size requirements, just be sure to let us know how you have modified the design to meet your needs so we can share it with others.