Joinery

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Mortise Layout

December 24, 2011 in Dining table, Furniture, Joinery | No comments

I typically use loose tenons for mortise and tenon joinery.  I find them to be much faster than a traditional M & T, plus it’s much easier to get accurate shoulders.  I use my Inca slot mortiser to cut the mortises.  It’s fast and simple to set up and it cuts a mortise in about a minute.

To lay out the mortise on the leg, I start by drawing the profile of the apron.  In this case, the outer face of the apron is angled.  I could get the angle from my drawing, but I prefer to get it by eyeballing what looks good as I draw it on the leg.  This angle will become the actual angle on the apron.

Once the apron profile is drawn, I draw the mortise.  I typically leave 1/2″ of material at the top of the leg, but in this case I cut it to 3/8″.  Because of the stresses on the legs and aprons as the table is expanded, I wanted all the glue surface I could get.  Smaller than 3/8″ could result in failure of the short grain at the top of the leg, so I rarely go less than that.

The photo below shows the layout.  Note that I only draw the complete layout in one location.

The other locations are only marked for the length of the mortise.  Why?  That’s all I need.  When I use my slot mortiser to cut the mortises, the height of the mortise above the table is fixed by the machine.  Once set, it’s the same for all of the cuts, so why waste my time marking more than I need to?

To maintain accuracy, I mark the mortise lengths using a combination square.  I use it like a depth gauge, with the head resting against the top of the leg.  The END of the blade is set to mark the lengths.  Once set for a given distance, I mark all the legs AND all the apron ends.  That way, every mortise is in exactly the same spot relative to the top of the legs.  Here’s an example of the apron end layout (this isn’t an actual apron).

Note that when marking the apron ends, the head of the combo square is only used to reference from the TOP edge of the apron.

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Dovetails

March 4, 2009 in Hall table, Joinery | No comments

I’m skipping ahead a few steps here.  As I stated in the previous post, there was a bit of work getting the drawer front to this stage.  I started with a piece of walnut, S4S’d it to size, then cut the bottom edge into the crescent shape.  I don’t want the front face to be flat, so I used a plane to “sculpt” it a bit.  The shaping is subtle and barely shows up in the photo below, but if you look carefully, the bottom edge (left side in the pic) is a little thinner.  It’s more apparent when you see it from the end.

The next step involved veneering the bottom edge; I did that by applying two coats of yellow glue to the veneer, letting the glue dry after each coat, then using a hot iron to re-activate and set the glue.  I used my vacuum bag to press veneer onto the front face, since it would easily conform to the surface.

Once that was done, I sanded everything to about 240 grit.  Then I carefully measured the drawer size and cut the drawer front to size.  I made an appropriately angled wedge, and used my shooting board to shoot the ends to the correct angle.  The dovetails came next.

As you can see in the photo, I’ma tails-first kind of guy.  I haven’t cut angle dovetails before, so these were a little more challenging than usual.  The drawer sides are angled in about 8 degrees (if I remember correctly), so the dovetails are similarly angled.  The photo shows the left drawer side in position to mark the pins.

 

Here is the dry-fit joint.  I’m pretty happy with the fit.

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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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Sliding dovetails

November 24, 2008 in Joinery | No comments

I previously discussed how I plan to join the sides, web frame, and bottom shelf here, using sliding dovetails.  They will provide a mechanically strong and invisible joint.  Before cutting the dovetail dadoes, I carefully cut the sides to length using my table saw and sled, with the blade tilted the requisite 11 degrees.  To locate the dadoes, I aligned the sides to the face frame and used a straightedge and marking knife to mark the position even with the tops of the rails.

I set up three routers with the requisite bits:  7/8″ straight, 3/8″ straight, and 3/4″ dovetail.  The jig aligns easily with the knife mark on the sides (assuming you put it on the correct side of the knife mark!).  I routed the 7/8″ dado first, after noting the rotational orientation of the router base in the jig.  Because the base is never perfectly concentric with the bit, I wanted to make sure it was aligned with the dado already routed in the jig.  A 3/8″ dado came next.  That is done to make it easier on the dovetail bit; less material to remove makes for a cleaner cut.  The dovetail bit was last.

After that, I cut the rabbet for the back to fit in, and trimmed the bottom corner of the rabbet with a chisel.

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