Jigs & fixtures

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Dining Table Legs

January 7, 2012 in Dining table, Furniture, Jigs & fixtures | No comments

I’ve already discussed laying out the mortises on the legs, but I forgot to discuss the creation of the legs.  So, let’s go back in time a bit and see how that was done.

I started with my SketchUp model.  I drew the legs in the model using the BezierSpline plugin.  If you use SketchUp you need this plugin.  It’s awesome.

I printed out the leg profile at full scale, which spanned three pages.  I carefully taped the pages together and, to my surprise, had a very nice drawing of the leg.  I would normally do this by creating a full scale drawing using ship’s curves, etc, but I was very pleased with this method.  Here’s a (blurry) photo of the drawing.

I took this drawing, laid it on a piece of 1/4″ Baltic birch plywood, and transferred the lines to the plywood by poking holes through the lines on the drawing.  I then connected the dots with the aforementioned ship’s curves.  The template, or pattern, was then cut out and the curves smoothed with a spokeshave and curved sanding blocks.  (In retrospect, I should have just glued the drawing to the plywood.)

Next, I created a pattern routing jig.  I use a large custom end mill for this type of pattern routing and the jig must be very sturdy to take advantage of the process.  This is not the place for double-stick tape.

Here’s a photo of the setup:

There are two jigs necessary for the process, and both faces of each jig are used to get all four edges of each leg.  It’s a rather complicated process which, in retrospect, was overly complicated for just four legs.  But it gave me four virtually identical legs.

I start the pattern routing process by using the 1/4″ template to trace the profile onto the stock.  In this case the material was 12/4 cherry, since the total width of the flared legs is 2 3/4″.  When tracing, I’m careful to draw the pattern about 1/16″ oversize on the edges and 1/8″ oversize on the ends.  Two opposite faces are then rough cut on the bandsaw.

The two bandsawn faces are shaped first, with the other faces left flat.  The template is then used again to draw the profile on one of the shaped faces, and the bandsawing and pattern routing is repeated.  This time, however, the leg requires extra support, as shown in the photo above.

Finally, the legs must be cut to length.  Since I know they are 1/8″ oversize on each end, I start by cutting 1/8″ off one end.  It was easy to start at the top end, since it has two adjacent flat surfaces where the aprons attach.  The photo below shows the setup for cutting the bottom end.

Note the spacers taped in place to get the correct configuration.  The tape on the end of the leg is there to prevent tearout on the backside of the cut.

Cutting Large Holes

December 15, 2011 in Jigs & fixtures, Tips & Tricks | No comments

Did you ever need to drill a large hole for which you didn’t have a drill bit?  Up to an inch, a twist, brad-point, or Forstner bit will work.  One to two inches?  Forstner bit.  Two to four inches?  Forstner bit also, but these are uncommon and expensive.  Four to eight inches?  Somewhere in there you can use a router and circle jig.  Hole saws can work in some cases, but they don’t leave a very clean hole.

I recently ran into this problem.  I’m updating my Inca slot mortiser fixture and needed to cut an accurate hole to hold my Porter-Cable 690 router motor.  The hole required is 3 1/2″.  I could buy a $30 Forstner bit, which I would use once and probably never use again.  (Okay, if I had purchased it eight years ago this would be use #2, but you get my point.)

Starting with the end in mind:  My goal is to create a pattern to use with a router and pattern bit.  I want a pattern, or template, with an accurate 3 1/2″ hole in it.

To create the hole, I need to start with something I know is round.  I can create that with my disc sander by rotating some material (I’ll use 1/2″ plywood) on a pivot.  The pivot, a 1/4″ dowel, will be located in another piece which I can manipulate on the table of my disc sander.  I want the outside diameter (OD) of the pattern to be large enough for the router to ride on easily.  Three inches of material provides plenty of support, so I’ll make the OD about 9″.

I start by drawing a circle with a compass and rough cutting on the bandsaw.  I then drill a 1/4″ hole in the center.  Another piece is drilled to accept a 1/4″ dowel, with the dowel located so that the pattern will be supported well on the disc sander.

Here’s the setup on the disc sander.

The actual size of the outside diameter isn’t important; what matters is that it’s round.  It’s easy to get a flat spot when doing this, so be consistent with your pressure and movement.

Once I have a good outside reference I can start on the inside diameter.  I draw a circle of the desired size and remove most of the material by drilling a few holes on my drill press.  I then use my saber saw to finish the task.

Next, I make a special fence for my router table, shown below.  The outside diameter of the pattern will ride on the two edges of the fence.  A straight bit routs the inside diameter as the pattern is rotated.  By moving the fence back, I increase the diameter of the hole.

Here’s the setup in use.

It’s important to rotate the pattern in a clockwise direction.  The edge being cut should move to the left, against the rotation of the bit.  Moving the other direction would create a climb cut, which could cause you to lose control of the pattern!

Note too that when you move the pattern away from the fence, you move it away from the bit.  This makes it easy to stop and start the cut.

Prior to having a real fence for my router table, I did this process by using two pieces for the fence.  The pieces were about 3″ wide and clamped on the back side of the router table in a position such that the END of each piece was used to guide the pattern.  Quick and easy.

Also note that moving the fence back makes the hole larger by twice the amount of fence movement.  If you move the fence 1/32″, your hole will increase by 1/16″.  It’s easy to overdo it, which I did when I was shooting this demo.  The nice thing about this technique is that it gives you a very fast way to cut a very accurate hole.  I did the second pattern in under ten minutes.

If you have a spindle sander, you could do this operation also, but I don’t think you can get the same accuracy.  But you may not need it, either.

In the next post, I’ll demonstrate how I used the pattern.

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Table Top Attachment

May 20, 2009 in Hall table, Jigs & fixtures | 1 comment

There are lots of ways to attach a table top:  cleats, buttons, figure-eights, pocket screws, Z-clips.  All work with varying degrees of elegance and effectiveness.  But none of them will work for my hall table; with the exception of the pocket screws, they all incorporate parts that would interfere with the drawer or would be visible from the exterior of the table.  I suppose some version of pocket screws would work, but that just occurred to me right now as I’m writing this…

I mentioned previously that one option would be to use a method similar to the frog attachment on a Stanley Bedrock plane (or Lie-Nielsen).  After lots of thought, I decided to go this route.  It appealed to my engineer brain; it was functional, elegant, and challenging.

The pins are 3/4″ brass, turned on my Jet mini-lathe.  The brass mills surprisingly easily with standard turning tools.  I located and drilled 7/8″ holes in the base, then made a locating pin using dowel stock and a dowel center.  The table top was already located via two 1/4″ dowels, so I installed the locating-pin/dowel-center in one of the 7/8″ holes, mounted the top on the 1/4″ dowels, pressed down so the dowel center did its thing, then repeated three more times with the locating pin in each hole.

I then mounted the brass pins using #10 screws, installed the top, and marked the pins with the locking screws (#8 x 2″ Spax screws) to get the correct height of the groove in the brass pins.  The pins were put back in the lathe and a groove was turned with my parting tool.  Each groove was located slightly off center from its locking screw in order to provide some hold-down force.

I hope that all makes sense…

Some photos:

Top attachment pins

Top attachment holes and alignment tool

Drill jig

The bottom photo show the little jig I made to drill the lock screw holes.  It worked great; all the grooves into which the lock screws protruded were at almost identical heights.

When I put the whole thing together, it works great.  The top feels very solid and is right where I want it.  I emphasize “right where I want it” because the other option I looked at was using keyhole hangers.  They would have worked, but I was concerned about the lack of a fixed location and getting them all equally tight.

Despite the extra work, I’m very happy with how it came out.

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Drawing Arcs

March 12, 2009 in Jigs & fixtures | No comments

Just a quick post to follow up on a comment I left on Chris Schwarz’s blog.   Here are a couple of pics of a jig I made to create large radius arcs, based on a concept I learned from John Nyquist.  Jim Tolpin describes the process here.

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Mortise & tenon

January 31, 2009 in Jigs & fixtures, Joinery | No comments

The mortise and tenon joint could probably be considered the cornerstone of furniture making.  The dovetail is certainly prettier, but not nearly as common or helpful.  I can make tables, chairs, and lots of other pieces and never even think about a dovetail.

My preference for making a mortise and tenon joint is to use loose tenons.  I find them much easier and quicker to create, and the shoulders are always coplanar.  You have to make at least one mortise anyway; why not make two while your at it?  Then make the tenon using your planer, allowing you to sneak up on the fit.

I didn’t come to this decision without a lot of head-scratching.  I made lots of M&T’s before getting here, and have taught lots of students how to make them.  My thoughts on some other methods:

Mortise:  Hand chopped – Neanderthals only.  Drill press mortise, cleaned up with a chisel – too much work, but the simplest method in terms of machinery used (unless you don’t have a drill press).  Router jig mortise – not a bad choice if you have a decent jig, and a decent jig isn’t hard to make.  Hollow chisel mortiser – I have always had a philosophical objection to the “cutting” action of this tool, although I know they work well with a sharp chisel and bit.  Slot mortiser – the best method, but you have to own a slot mortiser, and the simplest ones are over $600.  Dedicated joinery machine (Leigh FMT, WoodRat, etc.) – not a bad way to go, but can be complex and pricey.

Tenon:  By hand – see previous paragraph.  Table saw/dado set/sled – works okay, but I don’t like the surface left behind by the dado set.  Table saw/tenon jig – works well, but multiple setups involved (although this is my second choice).  Slot mortiser – difficult to set up most of them to do this well.  Dedicated joinery machine – see previous paragraph.

And, let’s not forget about the square-end/round-end mortise/tenon issue.  I don’t typically make through mortises for Arts and Crafts style furniture, so this isn’t an issue for me.  Round-ended tenons work just fine; no one sees them anyway (not that I’m trying to hide anything…)

All that to say I like loose tenons.  Which means I own a slot mortiser.  Can’t do loose tenons easily without it.  Mine is an old Inca machine, originally intended to mount on the back side of an Inca model 259 (I think) tilting-table table saw.  That little saw was rock steady, with arbor bearings bigger than my Powermatic 66.  The problem with the mortiser attachment was the bit speed; it ran at the same speed as the saw blade, about 3400 rpm.  Very slow by router bit standards.  I purchased the trick Clico bits, which were supposed to work well at that speed, but the whole process was too slow…

Until I built a new jig around the mortiser that allowed me to use my router:

This thing rocks!  It cuts mortises accurately, quickly. and cleanly.  Messy and loud, but I can live with that.  I made the fixture of MDF, thinking it was a prototype and I’d make the “real thing” once I got the bugs worked out of it.  That was about six years ago…

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Miters

December 18, 2008 in Hall table, Jigs & fixtures | No comments

The face frame and sides of the cabinet are joined with a miter joint.  I was initially concerned that cutting the miter was going to be quite a challenge, especially on the face frame.  The stiles are tapered, so using my left-tilt table saw with the fence as a guide wouldn’t work.  I could have cut the miters before I tapered them, but I felt that was too early in the process to give me the accuracy I wanted.

At Cerritos College, where I teach, we use a method that was perfect for my project.  One of our students, Gene Leslie, saw the method on a web site somewhere (I wish I could give them credit).  It’s one of those methods you wish you had come up with yourself.

It requires a simple jig:  two pieces of sheet material, about 3/4″ x 2″ x (the length of your fence), butt jointed together with screws.  A cutout at each end of the horizontal piece allows the assembly to be clamped to your fence (see the photo).  The height of the jig is critical; the bottom should be 1/8″ lower than the thickness of the material being cut.  The fence setting is even more important.  It must be set so that the blade cuts the miter but leaves a very small flat on the top edge of the board.  If the flat is too big, you have to round the completed corner a lot.  If you have no flat, then you are inviting disaster.  That means that you have no reference for the workpiece to guide you on the back side of the cut; at a minimum you will get ”snipe” at the end of your cut and, worst case, you’ll get a kickback.  If you don’t totally understand this process, don’t try it!

I try to set things up so the flat is about 1/64″ wide.  It takes some fiddling and test cuts to get everything lined up just right.  Precision is key to getting a good miter, along with a sharp, clean blade and consistent pressure during the cut.  To make the cut, just push the material past the blade and against the jig.  The offcut will safely rest under the jig, safely out of harm’s way.  Note that if you just used a sacrificial fence flat against your saw’s fence, the offcut would be trapped between the sacrificial fence and the blade.  That would almost certainly create a serious kickback, involving a narrow, sharp-edged object.  Serious injury could result.

Note also that on my left-tilt saw, I have to put the fence and jig on the left side of the blade.  This is the only situation of which I am aware where a right-tilt saw is preferable to a left-tilt saw.  That explains why many cabinetmakers prefer a right-tilt saw.

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Structure

October 7, 2008 in Furniture, Hall table, Jigs & fixtures | No comments

Attaching the web frames to the sides on any cabinet presents many choices.  Dado, rabbet, sliding dovetail, spline, biscuits, screws, pocket screws, nails(!), all come to mind.  They all have pros and cons associated with them related to appearance, structure (there’s form and function again), tradition, personal preference, etc.  Compounding the problem in this case, the web frame and shelf attach to the sides at an angle.

I don’t want to see plugs on the outside of the cabinet, so that eliminates the simple and strong option of a dado and screws.  For this piece, nails are out of the question, and they aren’t that strong anyway.   Pocket screws would offend the aesthetics of the piece (and me).  I presented the options to my students, and they challenged me to use sliding dovetails.  Strong and elegant, they would be the best option, and the most work…

I have done this joint before, but not at an angle.  In this case, I needed an angled dado to house the end of the shelf (or web frame), then a dovetail in the bottom of the dado.  Two routers, with simliar bases, one with a 7/8″ straight bit, the other with a 3/4″ 14-degree dovetail bit can be guided with an angled jig along the inside face of the sides.  Here’s a photo of the jig with the router.

I drew a cross-section of the jig full scale to get the dimensions right.  The angle is 11 degrees, and the router base is 5 3/4″ diameter.  I used a Makita and a Porter-Cable router, both with P-C bases on them (Makita conveniently made their bases with the P-C bolt pattern).  I carefully aligned the bases so the bits were concentric, and here’s what I got with my test cut.

The dovetail on the end of the shelf piece was cut on a router table with the same bit that made the housing.  It took a few tries to get the settings right; there’s not a lot of tolerance in this joint.  Too tight and you can’t put it together, too loose and it rattles like marbles in a can.  When it’s right, you can barely slide the parts together, and getting it apart is a bear.  Too bad no one will see it on the assembled cabinet; the front will be hidden by the face frame, and the back will be hidden by the frame and panel back.

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Where to start cutting?

October 3, 2008 in Furniture, Hall table, Jigs & fixtures | No comments

Since the doors on the table/cabinet are limited in size to the veneer I made, the cabinet must be made around them.  With that in mind, using 1/4″ MDF as a drawing surface, I created a full scale drawing of the cabinet front.  Actually, I only drew half of the cabinet, but that will give me all the information I need to cut out the parts.  Without this drawing, it would have been difficult to determine the lengths of all these parts, since none of them are rectilinear.

The photo shows the bottom half of the drawing.  The bottom edge of the MDF is the bottom of the cabinet.  The drawing shows the front “faceframe,” the interior parts, and the joinery (loose tenons).  I can now lay the parts on top of the drawing and just transfer the dimensions to the parts.  The next step is cutting them.

The tapered stiles will be mitered on their outside edges, and I decided to cut the miters after the frame is glued up.  Doing it now would complicate the frame glue-up and make the parts more difficult to handle.  To cut the taper, I use a taper jig of my own design.

Unlike most taper jigs, mine is wider at the far end.  The stop is located there also.  This means that the workpiece is used to guide the jig through the saw, instead of the reverse.  Most taper jigs give you no control over the workpiece, and you must trust the jig to push the workpiece through the saw, despite the physics of the operation working against you.  IMHO, this just works better, and I see no downsides.

Here’s the completed frame with the doors in place.  Nothing is glued up yet.

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