Wednesday, June 24, 2015

Chair Build Days, Oh Heck I've Lost Track

I have lost track of what day I'm on or what day it is.  I am happy to report I have replaced my computer and I am back online.  I chucked the PC for an iMac and have a bit of learning to do.

Medial stretcher fit to side stretcher
Since my last post I drilled and assembled the under carriage of the chair.  In the past I have done my boring with a bit brace and either an auger or spoon bit.  For this chair I used a battery operated drill with a brad point bit that I ground specifically for the purpose of building chairs.  Pete Galbert covers grinding bits in great detail in his book Chairmaker's Notebook.

Drilling the leg for the side stretcher.  I removed the drill for clarity.
In the photo above I am using a method I have been using for awhile now.  I first read about this on Pete's blog and decided to give it a go.  I found it to be very accurate and much easier than my old way of measuring.  I will probably not do justice with my brief explanation but here it goes.

After the legs are reamed and placed in the seat I put painters tape on the legs running with the centerline from bottom to top ensuring I cover the area where the side stretchers will be placed into the legs.  I place the piece of plywood with a predetermined angle (I believe this one is 72 or 74 degrees) against the two right legs.  Using a carpenters pencil laid flat on the plywood angle I draw a new centerline on the tape.  Repeat the process for the left legs.

Next I place a leg in the V-Blocks and adjust the blocks so the new centerline is parallel to the bench top.  I set the board upright resting on the angle cut on the board as seen in the photo above, and use it as a drilling guide.  It is very important to remember to put the top of the leg toward you and then drill.  This will ensure you are drilling the mortise in the correct plane.

The advantage of drilling using this method alleviates having to measure each mortise angle for each leg and allows you to drill one angle that is easily repeated.  It is possible because a new average centerline was drawn onto the leg and used as the basis for drilling.  If that is as clear as mud I understand.  It took me a few times reading it on Pete's blog before it sunk in.

The H-Stretchers are assembled and the legs set back in their mortises preparing for the glue-up.
Next comes the glue up.  I assemble the stretchers in their H-pattern ensuring that the ends marked for the back legs are on the same side.  I use the bench to rotate the side stretchers so that the ends going into either the front or rear legs both touch the bench top.  This ensures that the stretcher assembly is square and will easily fit into the leg mortises.

I number each leg and the corresponding mortise.  When I glue the legs to the stretchers I start with #1 and continue to #4.  When all four legs are glued onto the stretcher assembly the tops of the legs will not fit into their mortises.  They will sit on the underside of the seat just to the inside of the reamed mortises.  This is due to the rake and splay of the legs.  Next I applied glue to the leg mortises and tenons, and with a little pressure the legs will flex enough to enter the mortises.  Then with great care seat the legs into the mortises up to the depth lines that were established when fitting the legs.

Prior to gluing the legs onto the stretcher assembly I used a saw to cut a kerf for the wedges into the top of the legs.  These kerfs are approximately 2/3 the distance from the leg top to the depth line.


Legs before wedges are inserted.
In the photo above you may have noticed that the kerfs for the wedges are cut perpendicular to the grain of the seat.  If they were cut parallel to the grain it would be very easy to split the seat when inserting the wedges.  I cut my wedges slightly wider than the mortise in the seat.  I do this so that when I drive the wedges into the kerf the little bit that comes into contact with the softer pine seat acts like a key and helps keep the legs from rotating.  Wether it is needed or not is debatable but it gives me a warm fuzzy feeling so I do it.  Another important note is to put glue on only one side of the wedge.  This will keep things from splitting when there is seasonal movement of the wood.

I use hide glue and only hide glue.  I have used Titebond or even Elmer's glue in the past, but the problem is that tight parts will seize quickly and sometimes before all parts are where they are supposed to be, and that will make one loose their mind.  I use an inexpensive hot pot with a plastic container (cut down Solo cup) to heat my glue to the optimal temperature of somewhere between 110 - 130 degrees.  I don't mix my own glue, I really like and use Old Brown Glue.

My $20 glue pot works like a champ.

When driving the wedges into the leg top it is important that the leg is positioned vertical so that the hammer blows to the wedge travel directly through the leg into the bench top.  If the chair was allowed to remain on all four legs while driving the wedges the indirect pressure of the hammer blows could cause the leg to split out below the underside of the seat.  Ask me how I know this.  I allow the freshly glued up undercarriage to dry for at least 24 hours, so the glue will reach its full strength, before cutting the wedges and trimming the legs flush to the seat.

Wedges in place.
Seat with its undercarriage.
This evening I had a few minutes so I pulled some oak,  that has been soaking for quite a bit, from its watery domain.  When I lifted the lid, well lets say WOW!  Its a good thing this blog isn't equipped with smell.

Wet spindle stock.
I carved out the 4 short spindles into octagons and set them aside to dry.  Rehydrating the oak has made it much easier to carve and to follow the long wood fibers, than it would have been if it were worked in an air-dried state.

Short spindles in their octagon shape.
Next I will finish the long spindles and then it is a matter of letting things dry for a bit before I place them in the kiln (read shop attic) to super dry.  While this was to be a June Chair Build it looks like this is going to be more like a June and July Chair Build for me.

Our host for this event, Brian Eve, has gotten his chair underway and it looks like it is going to be a nice one.  Go check it out here.

~ Ray Schwanenberger