L-Fence - #3 Plastic Laminate, Guide Blocks & Starting Knobs

In operation the “L” fence assembly slides up and down between a pair of end guide blocks.  To make the sliding operation smooth the ends of the adjustable backer and its mating edge on the guide blocks get faced with a smooth plastic laminate.  The drawing below has red arrows pointing to the faces that will get the laminate.

These laminate strips are made from a cutoff left over from a previous project.  Because the laminate is thin and brittle to reduce the chance of breakage when being cut a sandwich is made with a couple of sacrificial pieces above and below the laminate like this.

Once the rough blank is cut next is cutting the slightly oversize narrow strips that get glued to the ends of the pieces.  This is what the sandwich looks like with the top piece removed.  Here the first strip is used to support the left edge of the top sandwich piece so it does not rock when the cut is being made.

The just cut strips of laminate get glued to the plywood edges using contact cement.  The photos show how they are being clamped while the cement cures.  In the bottom photo the two end blocks are clamped face to face and you can see how the laminate is a little oversized.  It’s oversized because once the contact cement is applied to both surfaces and allowed to set when you put the laminate on the plywood it grabs instantly and no adjustment is possible.  Once cured the laminate will get trimmed to fit the plywood.

Trimming the laminate is done using the small router with a straight bit that has a guide bearing on the end guiding the laminate cut flush with the oak plywood.  Below the top photo shows the router, its bit and where just a short section has been trimmed flush.  The inset photo is a close-up view of the router bit. The bottom photo is after all the laminate has been cut flush with the oak.  Because the just cut laminate edge is sharp, I need to break the edge with some 220-grit sandpaper.

Drilling mounting holes for the screws is next.  That’s done on the drill press with a bit that cuts both the pilot hole for the for the screw along with a countersink for the head.  The insert photo is a closer look at the bit itself without the stop collar.

Once the holes are drilled, the guide blocks get attached to the backer board.  If you look closely, you can see where the blocks are a little long extending past the ends of the backer board.  That’s done so once they are glued and screwed in place, they can be trimmed to final length using the chop saw for a perfectly flush end.   I started by attaching the right one first.  After that the adjustable part of the jig gets set in place then the left block is brought up tight enough so the adjusting assembly can move easily but not loose enough to wobble.  The goal is to have the a fit where the piece moves easily but snug enough so the blocks keep the piece parallel to the bottom of the jig.

Next is to make four knobs shown in the drawing below.  Two are used to attach the “L” fence to the table saw’s rip fence straddling assembly and two are used with the adjustable part of the “L” fence.  I start by taking some thin pieces left over from resawing oak for other projects and gluing up three layers so the grain in the center piece is at 90 degrees to the face layers, just like plywood.  This will give the knobs some additional strength to resist splitting along the knob’s long dimension.  You can see the three layers in the left photo below.  The lower right photo shows how the piece will get cut into six knob blanks including the saw kerfs.

After cutting the blanks out a ¼” square hole (mortise) gets cut partway through the knob blank for the square part of the carriage bolt to fit in.  Below in the left photo you can see how the threads in the bolt transition into a square shoulder underneath the bolt’s head.  The right photo shows the mortising machine setup used to make the partial depth square hole with the mortise just started.

After the square mortise gets made a hole for the threaded part of the bolt is drilled through the blank.

Laying out the curved sides of the knob is next and to do that the pattern in bolted to the knob blank and it’s outline traced.  Below is a side and top view of what that looks like.

With the knob shape drawn on the top the curved edges get made using the large disk sander.  The bottom photo is a closer view where the closest edge is almost to the line but not quite.  The face up against the sander is just getting started.  I don’t completely finish one side before starting on the second side because as the piece gets sanded the wood heats up and can burn.  Working back and forth gives the sides a chance to cool off a little reducing the chance of burning the edge while sanding.

When that’s done it’s time to route a small radius on the top and bottom edges softening them.  In the bottom photo you can see where the top has been finished and the bottom is ready to go.  When the top and bottom routing is completed, the vertical edges will still be sharp.

Rounding those sharp edges is next and that’s done using three hand sanding blocks loaded with different grits of paper.  Last is some hand sanding using a small piece of 220 grit sandpaper to knock off the points where the horizontal and vertical rounded edges intersect plus do any blending as needed where the routed edges meet the flat surfaces.  The photo below shows each of the four steps needed to go from the mortised and drilled blank to a shaped knob.  These will get set aside for a while before the carriage bolts get installed.

Next Up – “T”-nut & Threaded Insert Installs – Finishing

L-Fence - #2 Stopped Dado, & Slotting Adjustable Backer plus Beveling “L” Piece

Cutting the fixed and adjustable backer pieces are next.  They get made out of a piece of ¾” oak plywood I have on hand.  Before cutting them the tablesaw blade needs to be changed from the rip blade on there that’s used to work on the “L” bracket glue-up.  Below the top left Glue Line Rip blade is what I use for cutting along the grain of the wood.  An edge view of it is the left blade in the inset photo.  To keep the plywood veneer from splintering during cutting the tooth profile and count is quite a bit different from the rip blade.  It’s the Precision Crosscut lower left blade and its edge view is the inset’s right blade.  A compromise between the two is the top right “Combination” blade whose edge view is the center blade.  Most of the time the Combination blade is on the saw unless there is a lot of ripping to be done.  The Precision Crosscut gets used only on veneered plywood or when crosscutting solid wood.

For the adjustable backer part, a piece of oak plywood gets cut to rough width and final length then a stopped groove is cut. 

The groove is 5/16” wide and a tad over ¼” deep.  It’s cut using a ¼” diameter bit in the router table by making two passes adjusting the fence between them.  These photos show the first pass completed.  The first cut does not meet the line closest to the fence because it’s just a rough reference line.  The actual accurate cut location is set using a scrap piece and dial calipers.

To get the required 5/16” width the router table fence is adjusted and a second pass made.  The completed routing is shown in the top photo.  The bottom photo shows the squared off dado end and the wood chisel used to trim it.

Cutting the tongue on the piece of oak that has already been laminated so it fits in the stopped dado is next.  This part is shown in the drawing below.

Here the rough layout lines have been added to the oak piece.  Like the dado these are only guide lines.  A dial caliper is used to measure progress on the left cut so I end up with a flush joint.  The right cut will get made gradually until the tongue fits in the dado.

The router bit gets changed from the straight ¼” diameter bit used to the bit shown below.  This bit uses different guide bearings shown on the left and right of the bit to make various fixed width cuts from 1/8” to ½”.  Since I wanted a ¼” width cut all I had to do was pick the appropriate bearing. 

This photo shows after a single pass has been made on both the top and the bottom.  Additional passes will be made on the bottom until the height of the cut equals the distance the stopped dado is set back from the edge.  Once that’s done the piece will be flipped over and additional passes on the top will be cut until the tongue fits in the stopped dado.

Here the tongue has been cut to its final size.  The piece of masking tape on the part is because the blank is about .002” thicker at one end.  Because the tongue is cut referencing the faces it has that tiny .002” taper from end to end.  The fix is to add the strip of masking tape on the thin end then raise the router bit .002” and make another pass across the router bit.  The result is a .002” cut which tapers to nothing at the taped end making a perfect fit.  This photo also shows where the last inch of the tongue has been removed so it fits in the stopped dado.

These two photos show different views of the stopped dado in the plywood part and the tongue on the laminated oak part.

These photos show the table saw set to cut the beveled edge on the laminated oak part.  Here the straddling assembly is attached to the table saw rip fence to add a little height providing additional support when the laminated oak part gets beveled.  The yellow magnetic fence is set to apply a little pressure to the oak piece to help keep it tight to the rip fence.

Once the bevel is cut the two pieces are put together for a test fit which looks like this.

Next is using the router to cut slots in the adjustable backer.  These will allow for the vertical adjustment of the backer and laminate oak piece.  In the drawing below the red arrows point to those slots.

To make the slots a ¼” diameter router bit is used.  Once the router fence distance from the edge of the backer to slot is set left and right stops are clamped to the fence and the first shallow cut is made.  In the photo you can see the right stop.  Because the slot is off center one end needs to be cut from the front and the other end needs to be cut from the back so they match.  Unfortunately, I cut the first pass on one of the faces from the wrong side so the slot ends were reversed from what’s needed.  Fortunately, the fix is pretty simple because the first cut was quite shallow.  A thin piece of oak gets cut to fit, glued in place then trimmed flush with the face.  The red arrow in the photo points to the completed fix.  If you look just above the slot, you can see where I added, “cut this side out” to prevent a repeat.  Since the slot needs to be 5/16” wide and the router bit is ¼” the fence gets moved away from the bit so the slot can be cut wider.  It is important to move the fence away from the bit so the piece needs to pushed toward the bit to make the cut.  That way the rotation of the bit does not pull the piece toward the bit.  If the fence is pushed toward the bit, then the rotation of the bit will pull the work toward the bit which can grab the piece and rapidly pull it into the bit.  If that happens then the process can get away from your control and before you have a chance to react things go bad in a hurry.

Here the adjustable backer’s slots are done and the “L” fence is set into the stopped dado.

Next Up – #3 Plastic Laminate, Guide Blocks & Starting Knobs

L-Fence - #1 Background & Glue-up

If you have followed many of the projects in this blog you will know that I frequently use a sacrificial fence when cutting tenons or making rabbits.  The usual method is to clamp a scrap piece of plywood or similar to the table saw rip fence and bury a part of the dado blade in it.  For example, if I needed a 15/32” wide rabbit a ½” wide stacked set of dado blades would be used with 1/32” of it buried in the sacrificial fence.  That looks like this.

The problem with that is over time the sacrificial fence can get chewed up as different depth and height dados get cut.  To get around wasting fence material plus adding some straightening, tapering and pattern cutting functionality I decided to make an L-Fence using one described in Fine Woodworking as a starting point.  Here is what the SketchUp 3D model looks like with an exploded view on the bottom.  In operation the center section gets adjusted up and down depending on the need.  More on the functions later.

To use, the jig gets attached to a fence straddling assembly I made some years ago for another purpose.  The assembly fits over the rip fence and is held in place with a couple of toggle clamps.  You can see the clamps in the right photo (green arrows).  The assembly also has seven attachment points for bolting jigs to it.  In the photos the red arrows point to “T” nuts at some of the bolt attachment points.

In the top drawing below the L-Fence has been bolted onto the fence straddling assembly and the center section has been adjusted so the table saw will cut a rabbit narrower than the dado blade stack.  The bottom drawing is a closer view showing how the board rides along the edge of the L-Fence while clearing the blade (dark red).

In these working drawings I did dimension all the pieces but they are more for guidance rather than targets that need to be hit exactly.  Most important is the nesting of the parts, clearances and the need for aligning holes between pieces.  To accomplish that I start with the “L” part of the fence and generally work my way back out toward the back mounting board fitting pieces as I go.

The “L” part of the fence will be made out of red oak.  Sorting through my leftover bin of scrap oak I pulled out a stack of potential candidates shown in the bottom photo for making the glue-up .  There is more here than needed but some have flaws like splits or cracks that may not be able to be worked around.

After excluding those pieces with flaws there was still plenty to use.  Fortunately, none had any twist or any real cupping.  However, about half of them had a bit of crook or a sideways curve to them.  That can be taken care of by clamping my 8’ level to the table saw’s rip fence and using it as a long reference surface.  The high side of the piece is placed away from the level as shown in the left photo.  That edge is then cut giving me a straight edge.  The piece is then flipped so the new true edge is against the level and the bad edge is cut staight.  There are a couple of constraints with this method.  First, the piece can’t be longer than half of the length of straight edge used or with my 8’ level no longer than 4’.  That’s because the high corners have to be in constant contact with the straight edge to make a true cut edge.  Second, the piece cannot rock when placed against the level.  If it does the cut edge will not end up straight.  The right photo illustrates the single point of contact at the end.  The other end provides the second point of contact.

With the crook removed next is gluing the first two pieces together.  Most of the time when gluing up multiple pieces it’s the narrow edges that get glued together like in the top photo below from the Porch Swing/Glider.  In this case two wide pieces are glued edge to edge.  Because of the pieces width they are stiff enough the clamping won’t distort the pieces so the glue line and edges will remain straight.  As pieces get narrower, they get more flexible and aren’t stiff enough to keep the glue joint straight.  The bottom photo shows rockers for a Maloof style rocking chair made from ten thin layers glued and bent around a form.

My point is these pieces while thicker than the layers used in the rocking chair it is still the thin dimension getting glued together.  As such I felt it was possible that the overall straightness could be compromised during clamping.  To make sure they stayed straight while gluing I decided to use the top of the workbench as a flat reference surface.  That’s done by first setting down a piece of 6-mil poly sheeting to keep the pieces from being glued down to the workbench if I get carried away with the glue.  Once the glue is applied the pieces are clamped together using the front rail of the workbench as a clamping surface.  Shown is the first of three sub-assemblies.

There is one other quirk to this sub-assembly glue-up.  It didn’t cause a problem in gluing them together but was different.  That’s because the two pieces used here are cutoffs from a tapered leg so they have a taper running from end to end.  In the top photo I drew a pencil line along the joint so you can see what I mean.  The bottom photos show the left and right ends of the piece.  Since the taper in both pieces is the same the finished top and bottom surfaces ended up being parallel.

Two more two-piece glue-ups finished the sub-assemblies.  Once these sub-assemblies are cut to a consistent thickness the three of them get glued together using the same process as before.

After the glue cures overnight, the blank gets run through the thickness sander to flatten out any irregularities and the ends get trimmed square.  As mentioned earlier the dimensions for most of this project are guides.  That’s true in this case as this piece for the “L” bracket was listed as ¾” thick but ended up at 1 1/16”.  I had hoped for a 1” thick slab but this will work out better.

Next Up – Stopped Dado, & Slotting Adjustable Backer plus Beveling “L” Piece

Wood Hold Down - #3 Making the Knobs & Finishing

Starting on the knobs used to tighten the hold down in place is next.  This begins by taking some thin pieces left over from resawing oak for other projects then gluing up three layers with the grain in the center piece 90 degrees to the face layers, just like plywood.  This will give the knobs some additional strength to resist splitting along the knob’s long dimension.  You can see the three layers in the bottom edge on photo below.  Once glued the plywood block gets divided into three more or less equal width blanks and cut using the bandsaw.

After cutting the knob shape laid out on one it’s back to the bandsaw to cut it out.  In the photo below I have just finished making the last cut on the prototype.  To keep my fingers away from the blade one of the quarter sawn white oak deep reach Cam Action clamps I made is used.

After being rough cut on the bandsaw the large disk sander is used to smooth and shape the edges.  When satisfied with the shape it’s checked to see the part is symmetrical and used to trace the shape on the other two knob blanks.  They are cut out and sanded to final shape just like the prototype.

Using a small drill bit in the drill press a center locating hole is made.  It will be used to mark the centers of the other two knobs and then for centering additional drilling operations.

To transfer the center-point the knob with the hole is stacked on top of another knob then both are clamped together so the edges are aligned and a drill is used to make a shallow hole in the bottom knob.  The same process is used for the third knob.

Completing the drilling is a two-step process.  First is to take a flat bottom Fostner bit and drill a hole ¼” deep.  This is for the ¼-20 nut that gets epoxied in there.  The second step is to drill a through hole for bolt access.  Both holes are drilled using the center reference hole drilled earlier.  Below you can see the drill bits and successive steps.

Epoxying the ¼-20 nuts in the recess is next.  This photo shows the nuts in with the epoxy covering them.  It’s a little messy looking but I wanted to make sure the gap between the flats on the nut and the drilled hole were completely filled as well as having the epoxy a little higher than the oak knob’s surface.

As you can imagine the threads in the nut get some epoxy on them.  The easy way to clean the epoxy out is to run a tap through the nut.  The tap follows the existing nut’s threads cutting away all the excess epoxy leaving a nice clean surface.  The top is still a mess and gets taken care of next.

Removing the excess epoxy is done using two sheets of sandpaper clamped to the table saw extension.  The reddish sheet on the left is 120 grit while the yellow sheet is 220 grit.  It does not take much time at all to sand off the excess epoxy leaving a nice flat oak surface.  Last, is to use the hand sanding block at the top which is loaded with 320 grit paper.  The bottom photo shows the finished sanded knob.  It also shows the three layers of oak in the shop made plywood.  One untended consequence of sanding all the surfaces smooth is the edges are pretty sharp.  Believe it or not I have cut myself on this type of edge so they need to be addressed.

There are a few ways to get rid of the sharp edge.  One is to “break” the edge by sanding it to either a chamfer or slightly rounding it.  However, in this case I wanted a softer edge so used a 1/8” radius roundover bit in the router table.  The photo shows the bit, knob and the safety gripper I use to keep my fingers away from that bit spinning at 15,000 or so RPM’s.

Once the routing is done the knobs get a little hand sanding with 220 grit sandpaper to smooth out the routed end grain and do blending as needed.  Below is a side and top view of a completed knob ready for its finish to be applied.  The side view shows a good view of the knob’s three-layer construction.

With the knobs ready for their finish, I can go back to complete the last bit of woodworking on the hold downs.  That's a slot to cut at the top of the arc for the bolt to pass through.  The bolt along with the knob applies pressure to the hold down.   The drill press is used to make the slot starting by clamping the hold down to the drill press’s fence and moving it until the center finder aligns with the slot’s punched center point.  That’s show in the photos below.

Next the center finder is removed and with the drill bit installed a hole drilled.  After that the hold down is slid over so the other end of the slot can be drilled.  A hole between those two is then drilled.  Here the end holes are drilled and I am ready to drill the center hole.

An additional pair of intermediate holes are drilled out then the hold down is slid back and forth with the drill fully through the slot.  This cleans up the inside faces of the slot resulting in the completed slot below.

Last is to break all the sharp edges of the hold down with sand paper.  Here is one of the hold downs with all woodworking done and ready to finish.

The finish consists of three coats of hand rubbed Danish Oil Finish.  I used this type of finish rather than my usual sprayed on lacquer as an oil finish can be rejuvenated down the line as the pieces wear a lot easier than a film finish.   When done this is what the completed hold downs look like.

Here is an example of one of the hold downs in use on a piece to be drilled.  In doing a little testing I think they will work well for light duty clamping.