How To: Making a Concrete Faux Bois Table; Part 1 
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PART ONE; the first installment of what will be a very complete tutorial over the next couple of months on the old and almost lost art form of Ferrocement Faux Bois.  Check back from time to time as more is added.   Several other tutorials are in the works that include technique & project-based lessons by a number of other nationally recognized craftspeople and artists in different fields and media as well.

The following text & pictures describe many of the techniques & shop tricks used to build the finished Faux Bois table in the photo below.  It is quite long winded as I have tried to detail as many of the different processes involved as possible in the hope that you will at least find some of the information useful.   Keep in mind that many of these techniques can be adapted to the production of just about any ferrocement item or sculpture.  So look it over and take from it what you will.   Get creative and adapt anything you like to projects or designs of your own.  And when you discover something new...share it.  Because passing on knowledge, especially to the next generation, is just about the most creative thing any of us can ever do.

 

All My Best,
Donald R. Tucker
Holland & Tucker


NOTE:   The following text & images are the sole exclusive copyrighted property of Holland & Tucker. Registered members of TheGardenArtForum.Com may feel free to print them out for their own personal use, however, they are not to be reproduced for publication anywhere, by any means, for any other use without the original author's written consent. 
© Copyright 2006  Holland & Tucker

Faux Bois

Faux Bois (Foe-Bwah);  French term that translates as "False Wood".  Refers to the large and very old schools of arts & crafts involved with imitating either wood or wood grains.  Faux Bois includes both sculpted three dimensional representations, as well as the two dimensional techniques employed by wood finishers to simulate the appearance of "fine" woods (walnut, rosewood, oak, etc.) onto "lesser" woods such as pine.  The sculpted three-dimensional ferrocement variety demonstrated here is also known by the Spanish term "El Trabajo Rustico", or "the Rustic Work". 

There are many different forms and finish techniques possible and the craft can be taken as far as you care to go.  From simple shapes quickly crafted in easy to work formulations...to highly complex forms and demanding mixes that are capable of yielding detail equal to the finest professional modeling clays.  And the finished products can be crafted to last outdoors for 50 years...or for many millennia.  It's all up to you, the artist, and what you choose to put into it.

This particular Faux Bois table was designed to resemble the old "lodge" style wooden furnishings that were created by regional craftsmen in America for hundreds of years.  It is finished in a medium-fine sanded concrete mixture and colored using acid etching stains that impart permanent color to the cement in the mix.  Its' simple lines are relatively easy to fabricate and with a little basic instruction just about anyone can duplicate this effort.  Properly executed, a piece like this can easily remain useful and functional for hundreds of years.  It can be produced using inexpensive & readily available materials that will yield a finished product that can either become a family heirloom or sold for a significant profit.  A finished piece like this can easily bring $2500 and more in many markets.  Faux Bois is scarce.  Antiques are incredibly expensive and becoming harder & harder to come by, and there are currently probably fewer than a half-dozen people in all of North America executing work in this art form.  Which I find a shame.   It is a unique, enduring and very rewarding means of expression that has been all but lost to time.  Not for want of buyers or practitioners mind you...but due to the secretive nature of most of the early artisans.  Sadly, they took many of their old world techniques & formulations with them to the grave, and some of them may never be rediscovered. 

Why I'm Doing This...

My mission is to try and save this old art form by insuring that another generation at least has access to what little information I have been able to uncover and build on.  And while Faux Bois is not likely to ever be "mainstream",  I do hope that some of you will give it a try.  Who knows.  One of you might be the one who rediscovers some of those lost techniques and uses them to create masterworks of your own similar to those who have gone before.  What masterworks, you ask?  Consider this;  A little man you have likely never heard of began practicing this art almost a hundred years ago.  His name was Dionisio Rodriguez.  He spent his life creating sculptures in concrete that celebrate the beauty and charm of ancient, weathered wood all across America.  Today, his works are treasured by collectors and officially recognized by no less than The National Register of Historic Places.  Not only for their artistry...but also for the enduring contributions many of his works have made to the fortunate communities in which they reside.  Amazingly, this little known craftsman today ranks second only to the esteemed Frank Lloyd Wright in having created the greatest number of works now listed on the National Register.  And there still remain numerous other works by Mr. Rodriguez that are slated for review.  Not bad for a little fellow who worked on his own and did it because he loved the craft.  And while he no doubt made a very respectable living at it, remember that art is like life...it is ultimately measured not by what you got from it...but rather by what you put into it.

In the beginning, there was...ferrocement?...

Ferrocement is simply concrete or any other cement-based media that has steel reinforcement inside it, so let's begin with the steel frame or "armature" as it may be known to the sculptors among you.  It is the "skeleton" that will provide form & support for the piece.  I use common "rebar" for most of my armatures.  It is a relatively soft iron rod that has cleats formed into its surface and is specifically engineered for use in concrete.  Other metals can be used, but it is important to understand that the metallurgy of rebar was designed to match the thermal expansion & contraction properties of concrete.  Not all metals do, and if the difference is too great, it can cause a failure of one or the other or both.   Rebar is available through most "Big-Box" home improvement centers as well as concrete specialty suppliers.  If you plan to use a lot of it, consider finding a specialty supplier as they will generally have a greater range of sizes, cleaner material (less rust) and better pricing.

Rebar comes in various lengths and is available in a wide range of sizes as measured by the diameter.  Often referred to individually as "sticks" or "rods", the size is commonly called out by the number of "eighths" that the diameter measures in inches.  For example; if a rod measures one-half inch in diameter...it is referred to as a "number four" because there are four-eighths in one-half of an inch.  Using this logic, a "number three" measures three-eighths...a "number five" five-eighths...a "number seven" seven-eighths and so on.  It really only gets confusing when there are an even number of eighths and you have to remember to convert, say... a number six to 6/8's and then again to three-quarters.  I have seen diameters as large as a number 18 (2.257 inches), but most of what I work with falls into the 3 to 5 eighths range.  There is occasionally a need for something smaller and I've found a quarter inch diameter related product called "pencil rod", or sometimes "smooth rod" that is very handy.  It is also available through specialty suppliers and has the same metallurgy as rebar,  but as the name might imply, has a smooth surface rather than cleats.  With that out of the way, let's take a look at what's inside this rascal...

Constructing the Armature or Framework...

NOTE: The image below shows the frame with galvanized metal lath attached, which will be discussed in a later section.

This table frame is made up of #3 rebar (that's 3/8ths, remember?) for all the top pieces & #4 rebar for the legs and crossbraces.  Three straight sections make up the legs, three straight sections that form the crossbraces between the legs, plus the top, which consists of two circular rings and three more straight support braces.  Additionally, three pair of small "standoffs"(6-total) were used to properly position the crossbraces.  Finally, the bottoms of each leg have a mild steel (ungalvanized) washer attached to help distribute the weight over a larger area than just the end of the rebar.  While this frame was entirely welded using a small, 110v mig-welder, it can also be constructed by simply "tying" the various segments together with soft steel wire.  All of the early examples of Faux Bois were constructed in that manner and the technique will work just as well today, however this tutorial will focus on the welded approach, as a separate tutorial will soon follow that will cover the different techniques involved in tying a frame.   Here are the "cut to" sizes for the different elements...

MEASUREMENTS OF COMPONENTS

Overall Final Finished Size:  29 1/2" Tall X 25 1/2" in Diameter

Please note that the following measurements are to accommodate the chosen finished size above for this piece.  Feel free to adjust as you like for a shorter, taller or different diameter table.

Cut Length of #4 rebar for the Legs:     3 pcs. @  27 1/4"

Cut Length of #4 rebar for theCrossbraces:    3 pcs. @  18"

Cut Length of #4 rebar for theStandoffs:      6 pcs. @ 1 1/4"

Cut Length of #3 rebar for the Large Top Ring:     1 pc. @ 77 1/4"

Cut Length of #3 rebar for the Small Top Ring:     1 pc. @ 39 5/8"

Cut Length of #3 rebar for Top Braces:      2 @ 11"  and  1 @ 23 5/8"

Outside Diameter of Washers:     3  @  1  3/4"

Sizing the Frame

When you design any framework you must take into account the thickness of the material you will be later applying .  In other words you need to subtract the thickness of the cementitious material from the final finished size in order to determine the correct size for the frame.  Example: If you want a table top that is 25 1/2 inches in diameter, and you want the edges to ultimately have three-quarters of an inch of cementitious material covering the frame...then the overall outside diameter of the frame has to be reduced by that amount...all the way around.  If you come in 3/4 " all the way around the circumference you wind up with a  measure of 24 inches for the outside frame diameter.  Likewise, any straight sections need to be shorter than the final finished size in a similar fashion,  allowing for whatever thickness you will be applying to however many ends.

Is there a minimum thickness of concrete material?  For conventional concrete, yes, around 3/4's of an inch to one inch . And here's why.  Steel embedded in ordinary concrete has the habit of creating what's known as "shadowing" if it is too near the surface.  Shadowing is a surface discoloration that is caused by either aggregates showing through or a faint migration of rust from reinforcing steel that is too close to the surface.  Generally 3/4's to one inch of concrete will prevent this migration.  "Densified" cementitious mixtures, such as those containing microaggregates like fly ash or special latex admixtures, can be applied quite thinly without shadowing occurring, but may be subject to breaking or chipping off if they are overly thin.  And, consider what any portion of the piece will be subject to in its lifetime in terms of wear or impact...and design accordingly.  Table tops & bottoms for example could be a little thinner than the edges, since its the edges & corners that will most likely be subject to impact damage.

Cutting Rebar

There are several ways to cut rebar, but whichever you choose, do it carefully.  Leather gloves and good eye protection are a must, even when using hand tools.  Razor sharp ends and tiny metal particles are an unavoidable byproduct of the cutting process.

Being quite soft, rebar can be readily cut with just a hacksaw and a little elbow grease.  Smaller diameters can also be cut using "bolt-cutters".  However, if you are cutting a lot of pieces or simply making a lot of cuts, an electric Chop Saw or Cut-Off Saw comes in mighty handy.  Just make sure to use a blade that is designated for use on steel and follow all of the manufacturers safety precautions.  When using a handsaw, secure your work firmly in a vise or similar clamping mechanism.  If you are using a Chop Saw and you want to cut multiple pieces to exactly the same size, fashion a "stop" against which you can position your work.  This will eliminate the need to measure, mark & position each piece individually.

Below is a picture of my home-made adjustable stop system.  Nothing fancy, just a few pieces of 2x2, and a clamp for locking it in place.  I merely premeasured the distance from the blade out on the "cut-off" side and marked the measurements onto a movable, sliding bracket.  Once set, I can cut one or one-hundred pieces precisely the same length without ever having to measure & mark them.  A real time saver for production work...but only if you measure the first one correctly.  Remember, "measure twice...cut once".

The arrangement above will slide in & out to accomodate lengths from 10" to 48" and is marked off in one-quarter inch increments.

If you are working on a wooden bench, you can accomplish the same thing by marking off the bench top in advance with a range of measurements and then nailing a temporarily wooden block at the desired measure.

Once the rebar is cut, it is a good idea to remove any notoriously sharp edges with either a file or sander/grinder.  It can save you a lot of bleeding later. 

And, while we're on the subject of measuring & cutting, here is the formula for determining what length of rebar you will need to cut in order to make a fully closed circle that is the finished diameter you want.

Measuring & Cutting to Make Circular Rings

Most people think of circles in terms of "Diameter", but in order to fabricate a circle out of a straight piece of rebar you'll first need to convert that desired diameter into a specified length to be cut. That happens to be almost the same as the outside circumference of that circle.  Acknowledging that it's been a while since many of us were in school...and...that there is a real-world catch your teacher probably forgot to mention ...let's start by getting a few terms straight.  It involves something that I still have to keep reminding myself to take into account.

Diameter is the distance ACROSS a circle at it's widest point, right?  Yeah but...unfortunately that doesn't take into account HOW WIDE THE LINE IS.  It's easy to forget, but it can make a big difference when you are working with anything wider than a skinny little pencil line.  So just keep reminding yourself that in the real world...objects have an INSIDE Diameter... an OUTSIDE Diameter... and, something I'm gonna' call...a Centerline Diameter.  Each has their uses, but only one of them will produce the length you need to cut.

Inside & Outside Diameters are pretty self explanatory, just easy to forget about.  If you have something like rebar, it has its own thickness.  Bend it in a circle and the measurement across the inside will always be smaller than across the outside by TWICE whatever thickness the material happens to be.  So anytime you have to cut anything that has any thickness and form it into a circle, you have to take that thickness into account.  To do that, start with the finished frame diameter you want as measured on the outside.  That'll be the OUTSIDE Diameter.  Then, if you SUBTRACT TWICE THE THICKNESS of whatever  material you are working with, that will give you the INSIDE Diameter.  Simple enough.  So then...what's that CENTERLINE thing about?...

The Centerline Diameter is the size of a circle running through the exact center of a circular ring of any three-dimensional material such as rebar.   And  that's the diameter you need to measure & cut to.  The CENTERLINE Diameter is determined by SUBTRACTING A SINGLE THICKNESS of whatever material you are using from the finished Outside Diameter that you want to make.   It is also the figure you use to calculate the Centerline Circumference...which is your  actual "Cut-To" length.

Outer Circumference  is the distance all the way around the outer edge of a circular ring.

Inner Circumference   is the distance all the way around the inner edge of a circular ring.

Centerline Circumference is the measure taken through the center of a circular ring.

"Cut-To" Length is the actual measure necessary to yield a given Outside Diameter and is the same as the Centerline Circumference...just straightened out.

Pi is the magical number that makes all this nonsense work...3.141592

OK...So here's how to calculate the Centerline Diameter Which is the Same as the Actual "Cut-To" Length...

Example:  You want to make a circular rebar ring that has an Outside Diameter of 24 inches and is made with 3/8 inch rebar...

  • Subtract one material thickness from the finished ring diameter you want to make --- 24" - 3/8ths" = 23 5/8ths" (or  23.625" )
  • Multiply 23 5/8" (or  23.625" ) x 3.141592 (Pi) and you get a Centerline Diameter of  77.220 inches which can be safely rounded to  77 1/4 "  (or 77.25" )
  • That's the straight line length you need to cut in order to form it into a 24 inch Outside Diameter circle out of 3/8th inch rebar.

Just remember to always factor in the thickness of the material you are working with and you'll always end up pretty close to the finished diameter you want.  Now...you confirm the cut length for the 13" O.D. small table top ring, also out of number three rebar.

Forming Circular Rings

These can be easy or they can be hard.  So, what's the "easy way" you ask?  Have someone else do it.  Seriously.  Many steel fabrication shops can whip rebar into a perfect circle in no time...but of course, they want to be paid for it.  But usually not very much at all if you do several at a time, so it is definitely worth looking into if you have such resources in your area.  If not, or if you simply prefer to do it all yourself, below are a few options...but first a few words about the material you'll be working with.  

A Few Things You Need to Know About Rebar...

There are several ways to go about shaping steel rebar that I will cover, but first, you need to understand a few things about the material itself.  It is a mild steel that can be readily shaped by bending & hammering.  Either way, you are basically stretching one side of the material while compressing the other.  Just be careful not to overdo it all at once.  Rebar has the nasty habit of crystallizing very easily which can cause it to shatter like glass with little or no warning when bent or struck.  This can be caused by improper tempering at the plant, overheating it when working it or applying too much force too quickly.  Bending metal heats it up.  If you've ever bent a piece of wire or thin metal back & forth until it gets hot and breaks, that's the heat changing the metallurgy and allowing it to fail.  Rebar (or any metal for that matter) will do the same.   So never overheat it by any means and then put it under stress.  When you do heat it, allow it to cool slowly & thoroughly before you stress it again.  And, for reasons I've never been able to fathom...heating rebar with a torch seems to induce crystallization...but welding it with a Mig or Stick welder welder does not (?).  Even though it often glows red using either of those methods.  So, in spite of the fact that I have absolutely no scientific basis for it...I hereby recommend against heating or welding rebar with an Oxy-Acetylene or any other kind of torch.  What can I say? It's just one more of life's little mysteries.  And if any of you out there know the answer or can otherwise bust this myth...please share it with the rest of the class.  'Til then,  just go slow & easy when combining heat & stress.

And finally, anytime you are working with rebar, the safest bet is too assume that it is going to "snap" or shatter at any moment.  So always use good eye protection and try to avoid any application of force that could send you flying head over heels if (when ) the metal fails.  OK...now about those "ring things"...what are some options?

Hand Bending, Hammering & Eyeballing It

As the name of the technique implies, this simply involves a little bending, a little whacking and then stepping back for a "look-see".  Not very scientific, but it gets the job done.  You can bend rebar around something...or use a hammer to pound it into shape.  Generally it takes a little of both to get it where you want it.  Whatever the method, it's a good idea to have something to work "to".   Make a template by drawing a circle matching the outside diameter of the ring you want to construct onto a piece of cardboard or scrap plywood.  At least then you will have something for your eyeballs to compare it to as you work.

A simple "bending jig" can be made with just a couple of large bolts by securing them into or through a sturdy worktop or even a handy beam.  By "large", I mean roughly twice the diameter of any rebar you want to bend.  Space them just far enough apart to get the rebar between them and position them in such a way that you will have plenty of room to continuously advance the material though them without it getting snarled in something else.  Insert one end of the rod between them and apply enough force to deflect it a little further than you want it because it will try to "spring back" just a bit.  Advance the rod further and bend again on the same axis, and again, and again, and again...until it starts to become more or less circular.   Try to make all of your bends in a straight line along one side and in evenly spaced increments.  If you twist or rotate the rod as you go you will wind up with a spiral helix.  Nice if you are scuplpting DNA but not for circles.   In addition to the cleats or ridges that go around the bar, most rebar also has two straight raised lines that run full length.  You can use these as a reference to help determine which way is "up" as you work.  Don't try to go "full-circle" all in one pass.  Work the full length to establish a good amount of curve, then go back and repeat the process until you are close to circular.  You can then compare it to the layout you drew and see where you need to add more curvature & where you may need to flatten it.  Paint pens are handy for marking any points where you need to make adjustments.   Put a mark on the inside where you need more curvature and on the outside where you need less.  These will then be your "strike points" for making hammer adjustments.

Should you need to flatten any areas or make small additions to the curvature, you can bend it by hand but are most often better served using a hammer to do it.  Lay the rod across the flat "anvil" area on a vise or any such hard, flat, preferably steel surface and strike it lightly on the outside of the curve where you want to lessen it, and on the inside where you need to increase it.  Adjust the pressure of your strike as needed and keep in mind that steel will always curve towards the side that you strike it on. 

While most any full-sized hammer will do, a 2 to 3 pound "cross-peen" is best suited for manipulating iron rod and is especially useful for making inside curves.  It looks like a small sledge that has a "V"-shaped head on one side with the sharp edge of the V running cross-ways.  With the cross-peen side of the head, a little patience and a little practice, you can coerce rebar or any steel rod into a whole host of complex shapes & forms.   Continue "finessing" with the hammer until the ends meet and you are satisfied with it's overall shape & roundness.

The ever-so-handy 3 pound cross-peen hammer.  Striking with the V-shaped head will cause rod to curve towards the side it is struck on.

Give Yourself A Hickey

You can also use a tool called a Rebar Hickey to make a circular ring.  It is a manual rebar bending tool that many home improvement centers carry in their masonry departments.  They are inexpensive and very handy.  Constructed of heavy steel, they have a triangular head with three thick posts protruding from one side for bending bar & a single post on the other that can be inserted into a hole (on a table top for example) to act as a pivot point.  The head is mounted on a handle about thirty to thirty-six inches long.  Here's what they look like...

Typical Rebar Hickey.  Found this one at Lowe's for under $20 bucks.

You can either use the Hickey "freehand" with the rebar lying on a flat horizontal surface with one end secured firmly and work you way along it...or place the turning post on the back of the head into a hole and "feed" the bar through it.   Once again, securing a large bolt into or through your work surface will suffice as a post to pry the rebar against.   As with the other methods, don't try to do it all at once.  Start as near one end as possible and just make a series of moderate bends at equally spaced points as you move along the rod.  Then just go back and continue "tightening" it up & comparing it to your layout until you are close and then finish it off with a hammer as mentioned above.

Build a Form

There are endless possibilities on this theme, so just look this over and adapt the basic ideas to your needs & situation as you see fit.  These ideas were observed in use by metal working artists over the years and are from memory, so take them for what they are worth.

One approach involved cutting out a single round disk-shaped form of plywood, attaching it to a work surface and then bending the rebar around it.  Works best when you have access from both sides rather than against a wall.

If you have a scroll or "saber" type saw, cut some 3/4" plywood into a circle to match the INSIDE diameter of the rebar ring you want to form (see above for calculating the Inside Diameter).   But, remember that a single form will really only be compatible with a single diameter of rebar.  Thicker rebar will naturally yield a larger outside diameter & thinner a smaller one.  Now measure in about 6 inches and cut out the center so that you have a 6" wide, flat "donut".  This is to accommodate securing one end of the rebar in place against the outer edge of the form by means of a heavy-duty clamp.  Note that you can use a smaller clamp by making the plywood ring thinner, but keep in mind that you will be applying a lot of force while bending.  I wouldn't recommend going less than three inches unless you permenetly "glue & screw" the ring in place onto a sound surface.  An alternative to clamping, is to set a heavy bolt (thicker than any rebar you will ever bend) into or through your working surface in such a way that you can tighten it down and secure the "starter" end of the rebar.  Just remember that this "locking mechanism" must secure the end well enough to hold the rod in place while you "wrap" it around the form .  From here you can add additional bolts about every 6" or so around the outer perimeter that are spaced just far enough out to allow the rebar to fit in and "rest" between the bolts & form.  This helps hold it in place and allows you to successively advance in increments from one bolt to the next without it springing back away from the form as you go.

The form definitely needs to be firmly attached to a sound & stable foundation like a heavy or built-in workbench.  If you don't have access to move all the way around it, you will have to adapt it in such a way that you can continuously rotate it or advance the "locking mechanism" as you go in order to complete a circle.

Another variation on this theme involved using a pair of disks to make a forming machine.  Trickier to build, but it seemed to serve the artist I saw using it quite well.  The version I saw was mounted vertically (perpendicular to the ground) on a large beam in his shop.  He had pre-cut several different sized disks and could use them to quickly form a wide range of "hoops" as he called them.

The disks he used consisted of two pieces of 1/2 " ply glued & screwed together  and each piece had been cut with a very slight bevel on the outer edge.  When glued together with the bevels facing inward towards one another, they formed a disk with a shallow groove around the edge that held the rebar centered quite nicely.   On the back center he had mounted a piece of two-inch galvanized pipe about a foot long with a flat flange fitting that secured it to the disks.  He would insert the pipe into a snugly drilled hole that ran all the way through the beam so that the pipe acted as the "axle" allowing it all to rotate.  On the outer face of the disk was another pipe flange with a threaded "Tee" connection through which he could inset a length of one-inch steel bar that served as the handle or lever by which he could rotate the whole thing.  I believe the two flanges were connected to one another with bolts running all the way through the plywood  and both flanges for added strength.  On the face of the beam were a series of pre-drilled holes that matched the various hoop diameters into which he would insert a large bolt to act as the bending post that forced the rebar to follow the curve of the disk as it was turned.  The "starter" end of the rebar was held in place by a fairly small (2 - 3" ?) "C" clamp which was mounted with the screw handle positioned on the outside of the disk and the stationery part of the clamp set into a hole a couple of inches inside the outer edge of the rim.  He would insert one end of a cut-to-length straight section of rebar between the heavy bolt and rim and clamp it down against the rim just behind the bolt so that it would turn without hitting it.  Once locked in place, rotating the disk forced the bar to follow the curvature all the way around until the two ends met.

He obviously had a fair amount of thinking & work involved, but could (literally) "crank" out one hoop after another very quickly and precisely.  I do recall that he also "finessed" the two ends as needed with a cross-peen hammer to achieve a good fit and finish to the joint where the two ends met. 

Rebar ends need to be ground to about 45 degrees before  positioning for welding.  The angles allow for filling in with a bead rather than building out.  Heat penetration is also much better.  Especially with a small rig.

Finally, prep the joint ends for welding.  Whether you are butting the ends of a ring together or attaching two straight sections into a "T" joint, you need to grind or cut a 45-degree bevel on the ends of the material in order to achieve a proper weld between them.  Simply building up a bead around the outer surface of the joint makes for a very weak & poor union.  The surface area around the weld needs to be relatively clean & free of rust as well.  Wire brushing is usually adequate or you can hit it with an angle grinder if you have one.

Fitting, Positioning & Welding

This will not be a complete treatise on the subject of welding...just a few basic considerations for those of you who may be new to it.  Reading up on the subject, some training and practicing with whatever rig you have access to are the only ways I know to gain any real proficiency.  You old pro's in the crowd probably already have your own tricks and are very likely much better welders than I, so feel free to comment, ignore or better yet...post and share your own thoughts on the subject in our Metal Arts Forum.  And as always, think safety in all that you do and use all the proper protection when welding...gloves, masks, etc.  Read & follow all the equipment makers instructions & precautions.  And if you think a high quality welding mask is expensive...have you priced a new set of eyeballs lately?

You can weld rebar up to about 3/4's of an inch with just about any kind of rig.  I have a little 90 amp wire-fed, gas shielded mig that plugs into an ordinary 110v outlet.  Not exactly a powerhouse, but adequate for these tasks and it's long since paid for.  You can also get by with most "cracker-box" stick welders as well.  Anything above this level just makes life easier.  I like my little mig because the head is quite small & can get in just about anywhere plus the gas shielding eliminates the smoke & gases that non-shielded "flux-core" welders are famous for.

You will also need a few steel faced clamps  to help hold things in position for welding (the rubber & plastic ones melt when they get really hot...go ahead...ask me how I know).  Vise-Grip pliers get me through most clamping & holding situations but occasionally the need arises for something that can maintain an angle or position without having to lock onto another section of the piece to do it.  There are devices called "holding magnets" that are designed for positioning work pieces that can do just that.  Some have fixed angles and look like big fat arrow heads and others that have adjustable angles.  Like so many crafts, welding is one of those that often requires more hands than most humans come equipped with, so be prepared to improvise as you go.  Here's a pic of both types of magnetic "helping hands".

This is a non-adjustable "holding magnet".  Sometimes called an "arrowhead" magnet, for obvious reasons.

This is the adjustable variety.  Very handy for odd angles. 

Another trick picked up from watching people who actually know what they are doing, is to fabricate some sort of Welding Table with a steel surface.  This will do several things for you.  First, it provides a good flat surface that's not easily marred or gouged.  Second, it allows you to connect your ground lead to the steel surface you are working on instead of trying to clamp it onto the often small & tricky to manage work piece.   And third, it's a lot less likely to catch fire than wood (yet another lesson learned the hard way).  My first was just a piece of 1/8th inch scrap steel sheet a couple of feet square screwed to a wooden table, but it worked.  I now have a small, all steel workbench that I picked up at a scrap metal yard for about $15 dollars.  At the same time, I also found a hefty chunk of thick plate steel that is great for pounding things on at a scrap metal price.  (I just love scrap metal yards! )

Welding the Table Tops Frame Rings

Once you have all the pieces cut and beveled where they will butt & attach (and a place to work), begin by welding the ends of the top rings together, closing the loops.   A pair of vise-grip pliers can be used to hold the ends in proper alignment while you "tack" them.  Tacking is the term used to describe welding just enough of a starter bead to hold a piece in place temporarily. 

Vise Grip pliers are handy when butting two ends together.

Once tacked, you can remove any clamps for better access to the joint to complete the weld or to adjust as needed with a hammer.  If it turns out that you aren't happy with the positioning, trust me, it's a lot easier to correct it now than it will be once it's fully welded.  Once you are happy with what you see, complete filling in the bead, let it cool, then "dress" the weld by grinding or filing off any excess.

Once you have both rings welded closed, they must be positioned so that the smaller one is as centered and as concentric as possible inside the larger one before mounting the support braces that tie them together.  The simplest way to do that is with another template.  But let's get some mileage out of this one.  Start with a piece of cardboard or light poster board about three-feet square.  Mark the center, then from that point draw a pair of circles matching the O.D.'s of both rings using a common center for both.  Then mark three equidistant points around the smaller circle (one every 120 degrees).   These will be your upper leg attachment points which you can transfer to the ring with a paint pen.  Now, if you extend a straight line out from the center point, through each of the three leg points and all the way to the edge of the template, you can also use it later as a guide to help determine the correct alignment for the bottom positions of the legs as well.  (NOTE: There will be an alternative to making all these templates at the end of this section.)

OK.  Now you can place the rings in position to match the circles and lay the table top support braces in place.  Make sure they are parallel, and then tack and weld all of the table top frame pieces together. 
Attaching the Legs & Keeping it All on the Level

It is very important that all three legs are mounted at the same angles out from center and that the table top is parallel to the ground.  (I know I just hate it when my Margarita keeps sliding off a tilting table top.)  

NOTE:  Now is a good time to mention "level".  Keep in mind that you will be measuring & adjusting things towards that objective from here on as you assemble the pieces.   So take a moment to see where you are starting.  Is the surface you are working on actually "level".?   'Cause if it's not, the table probably never will be.  Check it with a bubble level and adjust it as close as you can get it.  If you build it on a slant...it can be adjusted later, but only within certain limits without throwing everything out of whack.

The legs on this table are splayed or angled out from where they attach to the the inner ring at the top, outwards towards the bottom.  This is to provide both better balance, and to achieve the right "look".  And since the math & geometry necessary to figure all the angles & such are beyond my simple artists' mind...I chose to cheat and do it the easy way.   I just made a little wooden platform jig to hold the table top level and at the right height...then attached the legs.  Note that there are two different angles involved on each leg.  One being how much they slant out from center and the other being how perpendicular or square they are relative to the ground & top when viewed head-on.  Both of these need to be pretty close to "right" or the legs look a little too rustic.  If the top is level and the leg lengths equal, their angle out from center should all work out pretty close to the same.  The angle relative to the top & ground you can set either by "eye"...or with a square to the worksurface...or with a plumb bob hung from the top ring.  And, if everything is "right", the distance between each of the legs will measure out equally at the top inner ring and also equally where they meet the "ground" or work surface.  This is where you can use the template you made earlier with the three radial lines to help set the legs correctly.   It
is also one of those situations where the adjustable angle magnets I mentioned earlier are worth their weight in gold.  They can hold all three legs temporarily in place while you back up, scratch your chin and adjust them all.  But remember, you will be piling concrete onto this rig, so it doesn't have to be perfect, just very close.  Minor adjustments can be made by doing a little bending and /or grinding after they are welded and also as you build up the material.  But only minor.   When you are satisfied that the leg angles & spacing look acceptable, tack them securely.  Once they are firmly tacked in place, you can turn the whole unit over to make the weld areas more accessable and complete the beads.

Fitting the Crossbraces Between the Legs

On a "real" rustic table like this, the crossbraces that tie the legs together would be attached to the outside of each pair of legs and probably secured with something like a large hand-made spike.  Ours will just have to look that way.  The trick here is to make sure that the steel rebar that supports these crossbraces is positioned just far enough out from the legs so that it appears the two outer, finished surfaces mate and intersect one another properly after we are done building up the concrete on both of them.  That's why a pair of "standoffs" are needed on each crossbrace.  They must be just long enough to compensate for the final thicknesses of concrete on both the legs & the crossbraces.  If you were to weld the crossbraces directly to the legs and cover them both in concrete, the final appearance would be that they merged and pass through one another instead of just fitting up against one another.   The same is true anytime you are positioning intersecting elements.  You always have to consider how something will look later...after all the layers of concrete have been applied. 

I started this process by clamping all three braces in place roughly where I thought they should go and then just kept "tweaking" their position & angles until I was happy.  Since I was going for the "rustic" look, I intentionally put one of them a little more askew than the others, just for effect.  I then marked their positions on both the crossbraces and the legs with a paint pen and then removed them.  Using the marks as a guide, I then tacked all six of the standoffs onto the legs and then tacked the braces onto the standoffs.  After a final check for satisfactory alignment, all the joints were fully welded & dressed.

The final step in assembling this frame was the addition of a 1 3/4" O.D. weldable steel washer to the bottom of each leg.  Do not use galvanized or plated washers if you can avoid it. They will sputter badly, and welding galvanized metals gives off toxic fumes.  This is saved for last so that any minor adjustments to level and/or leg length can still be made.  Set the table frame upright on your now level metal work surface and check the "set" of the table top one last time with a bubble level.  You can now see if you need to raise or lower any of the legs to make the top just right.  You should be very close, but if you do need to make adjustments, there are a several options available.  Shortening is easy.  Just grind or cut of as much as needed.  To lengthen, you can either weld a little material onto the bottom of the leg as needed (Unlike wood, adding material back on is quite easy with metal)... or...if the difference is minor, you can make the adjustment when you attach the washer as described below.

Once you have corrected the legs or know where you have to lengthen, simply position a washer around the base of each leg so that the bottom end of the rebar sits centered within the hole and tack them in place. To correct a minor shortage on a leg, just raise it until the table top is level, then tack it to the washer across the gap to hold it in the raised position.  Finish of the welds and you are done.  Congratulations.  You now have a finished table frame.

Final Note:  An Alternative to Multiple Templates

After making dozens of single use templates that were very similar, I finally wised up and came up with an idea that has proven to be quite handy.  A kind of a "universal, one-size-fits-all" approach that replaces many of the templates I would otherwise be spending time fabricating.  It is simply a combination of common circle sizes, squares & angles pre-drawn directly onto my little welding table with metallic paint-pens.  As you can see in the image below, it is marked off in regular increments with many different sizes & angles ready for reference.  Any time I find myself repeating similar measuring tasks over & over, I just add them onto my table-top.

( An artist  friend once commented that the top of my welding table reminded him of the map they used in the movie "Time Bandits" to jump back & forth in space-time! )  Aw, come on... it's not really that complicated, is it?

END OF PART ONE

 


 

COMING SOON!

 

03.12.2008

My sincere apologies for not having the final parts of this tutorial in place by now.  But, life has thrown me a series of rather significant curves over the past year or two and I am just now getting back on track.  The "Good News" is that I will be teaching a "live, hands-on" class titled
"An Introduction to Ferrocement Faux Bois" in August of 2008 and will film the entire course.  A DVD of the complete course should be available by the Fall.  For information regarding this class visit The Ferrocement Educational Network at...

http://ferrocement.net/ferro/cal.php?pg=dx0x106


PART TWO:  Applying Galvanized Lath & Building Up The Base Layers

Then...

PART THREE:  Mixing, Applying, Sculpting & Detailing the Finish Layer

And, Finally...

PART FOUR:  Acid Etching A Permanent Color Finish & Sealing

 

STAY TUNED!  MORE IS ON THE WAY!

 

 

 

 

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