A Panel Discussion

Here’s the way I look at it:  Working with panels instead of boards is just another good excuse to acquire some new tools.  Besides, if you want to build anything of any size, panels are the only way to get the job done with a minimum of labor and maximum satisfaction.

A panel is simply a large sheet of wood made from several thin sheets of veneer glued together and cut to a standard size, usually 4 feet by 8 feet.  Call it plywood, because that’s what I’m talkin’ about, Willis.  It’s been around for over 5 millenniums, first used in Mesopotamia during a shortage of quality wood; the Ancients bonded quality wood to lesser-quality wood to make a product that looked good and filled the need.  In the 19th century, the son of the guy who invented dynamite developed the rotary lathe used to produce modern plywood, but the product hasn’t changed much over time.  Today, many grades and decorative “faces” are available to meet any woodworking need.

Panels are available in thicknesses from approximately 1/8th inch to one inch and thicker.  I say “approximately” because in recent years panels like other lumber have been shrinking in size due to manufacturers’ efforts to save a buck on raw material while providing a product meeting the needs of the market.  You must be diligent at specifying, or at least checking the thickness dimension of the lumber you buy today, as there is apparently no compulsion to standardize thickness, and you see different dimensions in similar products.

For example:  “Three-quarter inch” plywood at one time was, universally, 3/4 inch thick.  Not so any more.  Now thicknesses for “three-quarter inch” plywood might measure 11/16, 23/32 or 3/4 inch.  On really lower quality material, the thickness might vary over these dimensions within the same sheet.  The problem here is quality control and sloppy manufacturing techniques.

Regardless if you buy quality product or imported crap, measure the thickness to know what dimension you are working with.  One example of where this is important is routing channels to fit fixed shelves in a cabinet:  if you assume the panel is 3/4 inch thick and rout a 3/4 inch wide groove to accept the shelf thickness, and the actual thickness is something less, the fit will be sloppy.  Of course, this is the voice of experience speaking to you…

I have found a lack of consistency for similar products stocked at my local lumber yard over time because they buy from different mills and countries.  I have learned to measure thickness twice and cut once (hopefully), whereas once upon a time this could be trusted as a given.  Not so any more.

Along the same line, cheaply made panels have voids in the interior (core) plies, and sometimes lack adhesive in spots causing “blisters.”  Here are a couple of photos depicting extremes of quality in plywood:

The picture on the right is not too far off some of the stuff I have purchased in my effort to obtain stock for cabinet carcasses.  I usually am able to pull bowed pieces into flat sides and bottoms using screws and clamps, but I have returned pieces which should never have been on the retail shelf.  I completely changed horses in midstream on my latest cabinet project having found an unlikely source (Lowe’s) for a better quality maple plywood to replace my old birch standby which has increased in price and declined in quality significantly.  I had mercy on my lumber yard by keeping a birch panel which developed an S-curve within a week of purchase, because I knew they couldn’t/wouldn’t be able to resell it.  Their response?  “Thank you.”

Cutting panels to size for cabinets, chests, drawer boxes, etc. should be done accurately so the finished piece is square and well-built.  To do this requires careful measuring, marking, and use of a straightedge to guide the saw.

Alternatively, you could build your own panel saw from available plans for a few hundred dollars.  You typically see panel saws at cabinet shops and lumber yards where they will cut down a panel you purchased for a nominal fee.  The saw carriage and frame take up hardly any space, so if you use panels a lot, it might be a good time-saving investment.  Like any tool, you need to check it for accuracy, mainly squareness, from time to time to ensure cuts are plumb and parallel to the factory edges.

The kind of straightedge you use to guide your circular saw across the panel can be a shop-fabricated jig or a specialty tool.  I have used each and prefer the tool over the jig.  The jig is useful, but requires extra clamps, whereas the tool is self-contained.  Of course, the jig is made of scrap wood, so the cost is nil.

  To build the jig, cut two pieces of half-inch stock to the approximate widths depicted in the drawing, and lengths to match your application:  97 inches to rip full panels or shorter if you only rip 48-inch widths or less.  In any event, the bottom piece should be wider than the main (wider) shoe on the saw to be used with the jig.  Once the two pieces are glued together, run the saw along the edge created by the top piece to trim the jig to width.  (Place the wider part of the shoe on the jig when trimming for full support of the saw on the jig.)

The jig has a couple of minor drawbacks:  If you make it out of particle board, it will start to fall apart with repeated use. Secondly, you cannot use the full depth of cut of your saw because the half-inch stock the saw travels on raises the saw (reduces maximum depth of cut) by that half-inch.  Again, it was free…

                 The clamping straightedge saw guide is one of the cooler tools to add to your tool box; unfortunately it won’t fit in your toolbox, so you have to hang it on the wall…  It is also relatively indestructible, but it is possible to break the plastic part(s), or lose the roll pin if you try hard enough.  The guide itself is made of lightweight aluminum (aluminium to our readers in the U.K. and Canada.)  The sliding clamps are plastic and can break; the roll pin holds the clamp handle in place and can migrate out of its holes with use (just tap it home if it moves.)  With a little care, these issues are no problem.

The technique for cutting a panel accurately involves a few skills in which you are already gaining proficiency:  measuring, marking and measuring.  Yes, but this is a little different from simply measuring twice and cutting once.

First, turn the panel “good” side down.  Circular saws cut “up,” so this will give a clean cut on the good side; unless the blade is dull, the top cut should be clean, too.  Measure the distance between the outside edge of the saw shoe that will ride against the straightedge, and the inside of the saw blade.  Strive to be as close as possible, as this measurement will ultimately affect how accurate your final cut dimension will be.  So, measure to the blade overhang, also known as the side clearance, the outermost point of the kerf.  On many saws, this is a round number (thank you engineers.)  On my little Porter Cable Saw Boss it’s 4 inches precisely.

I can’t say enough about my little (6″) Saw Boss.  It’s made in the good old U. S. of A. for one thing (at least mine is…)  I bought it used at a pawn shop years ago, accidentally tumbled it down a 50 foot embankment (bent the shoe), and used it continuously over a period of 10 years in my business.  It has never missed a beat.  New they are not cheap, but worth the lifetime of service they give.  (Remember the ancient maxim about tools:  You gets what you pays for.

The six-inch saw is ideal for cutting panels:  It is relatively light-weight, albeit with a hefty feel, lots of power to cut through 3/4 inch plywood like a hot knife through margarine, and with a left-side view of the action for us right-handed wood butchers.  The best saw blade for cutting panels has a large number of teeth for a smooth, tear-out free cut.

Which brings us to the subject of:  Which side should you set up your straightedge on, left or right?   Or, another way to phrase this query:  Keeper or waste side of the panel?

Below is a depiction of the saw and guide set up on the waste (scrap) side of the panel.

See any potential issues with this set-up?  This is perfectly acceptable as a way to orient the equipment vis-a-vis the cut line.  (When I spell-checked “vis-a-vis,” the suggested revisions were:    bis-a-vis, via-a-vis, vi-a-vis, vs-a-vis, and is-a-vis.  What the h-e-double hockey sticks was that programmer smoking?)  However, what might happen if you, oh say, sneeze or violently fart while making your cut?  Where is your saw likely to migrate?  That’s correct!  Into “the Workpiece!”  Scratch one perfectly good $180-per-sheet aromatic cedar panel.  This stuff doesn’t grow on trees you know!  (oh, wait..what?)

Avoid this mini-disaster by setting up your saw and guide on the keeper side of the cut.  Then, if a dog  should bite you in the shop, you won’t ruin the good piece when you react by leaping onto the work table.

So…Remember the measurement from the edge of the saw shoe to the blade kerf?  Pull your tape measure from the corner of the keeper piece to the exact dimension you want the piece cut.  Now, subtract that measurement; in my case, it’s always 4 inches on the nose.  Make a narrow pencil mark at the edge of the panel and perpendicular to the edge.  Duplicate this mark on the opposite edge.  These two marks are your reference marks to align the clamping straightedge.  Practice aligning the straightedge at precisely the same spot on the reference marks, showing the same amount of pencil mark on each one.  To ensure the straightedge, and, hence, the cut will be perpendicular to the edge, measure back from the “wrong” side of the straightedge to the corner where you started.  Measure the other side, too.  These dimensions should be equal.  If not, double-check your work.  Practice will refine this technique, but following this routine will help avoid costly mistakes, like cutting a trapezoid instead of a rectangle.  (Can I get a witness?)

The shop-built jig is simply aligned with reference marks located at the dimension you want to cut, because the edge of the jig is where the blade cuts.  With the jig, it’s important to clamp the jig on the keeper side–not the waste side–to avoid cutting the piece too short by the width of the kerf.

The saw on the left  is getting a real workout.  Cutting the full depth of the blade is bound to put a strain on the motor, and will shorten its life if done consistently.  Careful attention to measuring and marking will ensure you can duplicate panel sizes (e.g., for cabinet walls) without stacking panels.  A way to preserve blade sharpness is to set the blade depth to exceed the thickness of the panel by one full tooth (about 1/8 inch) and no deeper.  This will present the maximum number of teeth in the cut while cutting.  Like a router, if it’s possible to push the saw against the guide rather than pull it toward you (like she’s doing), do it.  It’s easier to control and less work.

Support the panel on pieces of lumber to avoid binding the saw blade as the cut pieces separate.  Finally, leave the saw in place as it winds down to avoid binding the blade and/or marring the cut edge.

The edge of the panel shows the exposed plies, so something needs to be done to dress this up.  This is where edge banding comes in handy.

Edge banding can be purchased by the foot for smaller projects, or in rolls of 50 and 300 feet.  It comes glued for application with pressure or heat, or without glue.  I have not had the best luck with a variety of trimmers to remove the excess tape (edge banding is usually supplied in widths larger than standard plywood thicknesses.)  My tried-and-true method, although slow, is to use a razor knife to cut the tape against a metal putty knife as a backer.  The trimmers have a tendency to tear out the wood grain along the trimmed edge.  You also have to pay attention to the direction of the grain and push or pull the trimmer with the grain.  So, double edge trimmers are innately troublesome (to me, at least.)

Whether you are building a dog house or your dream kitchen, the ideal product for efficient and attractive woodworking projects has been around for over 5000 years.   What other wood-related thing can you say that about, except maybe the termite…

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