Replies

1. 
   joinerswork | Sep 06, 2008 09:00pm | #1

   Hi Jay,

   Are you fitting the armrest to the rear leg (stile)?  Not sure what you are referring to when you say, "side rail of the seat back"...

   If it is the rear leg you are fitting to: I rough-cut the notch in the armrest as you describe. The size and position of the notch is determined by how the top view of the armrest mates to the leg-- per a full-size drawing of the seat frame, arm pattern, and the rear leg's relative position-- above the seat frame, at the armrest's height. 

   I assemble the armrest to its upright, and fit the upright to the seat rail, coping the upright to fit the seat rail's molding.  Thus fitted, the whole ####'y can slide back and forth a bit while making the join above, at the rear leg.  If you have done your work carefully thus far (cutting and fitting the mortise and tenon joint of arm rest and upright, fitting upright to rail, cutting the notch) then fitting the notch is mostly a matter of angling the end grain face of the notch to match the angle of the rear leg. I like to do this by clamping the arm in place, and tracing around a shim of appropriate thickness, laid against the front face of the rear leg.  The thickness of said shim is equal to the gap between arm and leg at its greatest width.  It is usually 1/4" or so, and usually at the top of the armrest.  With a line drawn around the armrest notch, saw to the line, and offer the new face to the leg.  It might need some fine-tuning; marking the high spot(s) with a pencil, and paring with a sharp chisel will get you there pretty quickly. 

   Most old armchairs have the armrest let into a very shallow (no more than 1/8") mortise or recess cut into the face only of the rear leg.  Once you have got the fit of the notch satisfactory, you can scribe around the armrest onto the face of the leg, and chop the recess into which the armrest will fit.  Depending on the shape and pattern of the arm , and the size of the notch in its end, this recess might take the form of a shallow dado cut clear across the face, or it might be a rectangle or irregular trapezoid, beginning at the outside of the leg and ending partway across the leg's face.

   While cutting the recess might seem to be a bother and additional unnecessary work, I believe that it adds a good deal to the strength and appearance of the join.  First, it gives additional support to the armrest when the user pushes off the arms to rise from the chair.  The strain is transferred from the armrest to the rear leg, directly, not via the screw or bolt holding the joint together.  Secondly, the weak short grain at the end of the armrest is captured and protected in the recess, and this prevents splintering or crumbling of the delicate edge.  Finally, any gaps in the joint are somewhat concealed since, to see into the gap, one must be at the level of the arm rest, looking back toward the rear leg.  (Without the recess, one is looking down onto the join of the armrest to leg, directly into any separation.)

   Ray

1. 
   JayS | Sep 07, 2008 12:32am | #2

   Ray,

   Excellent discussion.  Thanks.  I did exactly as you described, but I made the mistake of cutting a right angle into the vertical support of the armrest, so I cannot cope it to fit the molding at the edge of the seat rail.  I also did not know about cutting a shallow mortise into the rear leg.  My joints are almost exact, and any gap is microscopic, but your comment about support of weight and protection of end grain are strong arguments to do it.  I attached my arm with the screws only, so It would be easily removed to cut such a mortise. I guess it's not too late.

    I didn't quite follow why the the mortise might be trapezoidal or might not continue for the full width of the rear leg.  It would seem to me the mortise would just go straight across the front of the rear leg.  Also, why would there not be a shallow mortise/dado on the outsides of the rear leg, to accommodate and support the other part of the right angle cut into the arm?  Thaks again.

   Jay

1. 
   joinerswork | Sep 07, 2008 04:27pm | #3

   Jay,

   "I didn't quite follow why the the mortise might be trapezoidal or might not continue for the full width of the rear leg.  It would seem to me the mortise would just go straight across the front of the rear leg.  Also, why would there not be a shallow mortise/dado on the outsides of the rear leg, to accommodate and support the other part of the right angle cut into the arm? "

   If the front of your notch is not as wide as the front of the leg, the recess will not go all the way across the leg.  And if the inside surface (facing the other arm) of the armrest isn't square to the top surface, i.e. bevelled or rounded under, its recess must be angled or curved to match.

   You could certainly recess the outside of the arm's notch into the leg as well.  but, since the termination of this side of the notch is usually rounded under (as is the whole outside edge of the armrest) it is more trouble to do so, and the benefits not as great. Also, be aware that moving the armrest inward by 1/8" or so pivots the whole assembly, and so will surely open a gap at the front of the upright's attachment to the seat rail...

   There are probably as many ways to attach the arms on a chair as there are makers to do so.  I've seen them tenoned into the rear legs with a 3/8" tenon an inch or so long (and repaired them when they broke along the short grain), also with a shallow (1/4" or so) dovetail slid into the outside of the rear leg. The upright is sometimes dovetailed or dadoed into the side seat rail. 

   Ray 

1. 
   JayS | Sep 07, 2008 09:27pm | #4

   So to summaraize, considering that I would have to re-fit the lower part of the vertical support to the seat rail (due to the wind or twist of the rail as it goes from vertical in the front to inclined in the rear), would it be acceptable to leave the arm connected to the rear leg only with the screw, and no mortise at all?  Would you say it is worth the extra work to try to create the 1/8 mortise and then deal with the slight rotation of the arm assembly?  I'm not sure how I would precisely plane that vertical support to match the twisted rail.

   Thanks.

   Jay

1. 
   joinerswork | Sep 07, 2008 10:16pm | #5

   Jay,

   Sure it's alright to leave things as they are.  The first few armchairs I built, I did them that way (not recess in the rear leg).  Haven't got one back yet for warranty work, that's going on 25-30 yrs...

   As far as fitting the upright to the seat rail, mark its location on the rail, then plane a flat on the rail if it has a hump or ridge there from the introduction of the twist. Then you can plane the inside face of the upright if need be, to come to it, using rabbet plane, shoulder plane and/or bench plane.  It can seem like you are chasing your tail, especially if you begin with a lot of fitting both at the seat and at the back leg-- move one place, it affects the angle and thus, the fit at the other, back and forth, forth and back.

   Ray