Tuesday, November 29, 2011

Putting the Chair Together Again

Here is the long and the short of it. And get ready for a long post.

It is unnecessary to mark all those little rungs and so forth because they can only fit properly back together one way. (Mostly)

There are two usual ways to make a chair.

One design has a frame that has the back two legs continue from floor to the top of the back, and a series of horizontal parts make it look more or less like a ladder, then there is a frame going forward to connect the front legs and support the seat. The seat can be integral as an upholstered cushion strung on bands of material attached to the frame, or an applied seat that rests on the frame.

This chair is the other kind.

This kitchen chair has a strong seat, which is the meeting point and holder for the back and the legs. It is similar to the centuries older Windsor chair style with a thick pine seat holding the legs and the back, which are usually made with maple and hickory or ash for the bent bits.

In this Quebec made piece, the thick pine seat is replaced by a thinner maple one of the same strength. The rest of the design is simplified but essentially identical to a Windsor, which is considered by many to be the apex of design using different woods for their unique properties in meeting the demands of a chair.

Take a look at the chair from the side. See how the seat slants to the rear for a more comfortable angle. More modern than the Windsor, the seat is made from Maple and carved by machine to that gentle contour that receives the grateful fundament as my grandmother called it.

 Maple is strong enough to do the work while being thinner. (Unfortunately, Maple is harder to glue than pine as it is so dense it absorbs little, and presents a smooth surface which is poor for grip.)

Note also that the legs are splayed out, farther apart on the floor than they are at the seat.

This means that the bottom rungs are longer than the top rungs. Which also means there will be a pair of long ones and a pair of short ones,  and then three extra.

The shortest extra will be at the back because the rear legs are closer together than the front ones. The two left over go to the front, longer one at the bottom shorter at the top. Simple, really.

Also note that the front legs are not only longer, but have some decorative turnings. Maple is excellent for turning and makes good legs and rungs.  Also some fancier chairs have the front rungs turned fancy as well.

Now lets fit some round pegs into round holes.

First look at a hole. Look at all of them before doing the glue trick.  Here is one:

See the dried glue at the bottom? It has to come out before the new assembly takes place. I use a small chisel to clean the sides and bottom.

I use a bigger one to treat the rungs before they go in. But first the clean out ceremony on all the holes.

There are a total of twenty eight holes in this chair. Don't believe me? Seven rungs - 14 ends, plus four leg holes and two back hoop holes in the seat, four back rungs with four holes in the hoop for them and four in the seat.

Not to mention four screw holes and two slots for wedges. A whole lotta holes!

The reason for the hardened glue at the bottom of the holes is simple. As the round pegs go in, they push a slug of glue in front of them that has nowhere to go, This hardened glue will prevent the next batch from moving out of the way of the rung, and might make the joint looser than it could be.

A quarter inch chisel takes care of the old glue.

Now about the new glue, and Mark's Method of promoting the best possible results.

First I treat the ends with my honkin' big chisel to make a series of thin wedge cuts at the ends of each peg that goes into a hole. See?

The reason for the little slots in the sides of the peg bits is to allow air pressure and glue to ooze back up and out of the hole if there is an excess that can't be accommodated at the bottom of the hole.

And the other thing I do is pay attention to where the glue goes. Glue works by sticking the sides of the hole to the sides of the rung, and the rung almost never gets to the bottom of the hole. So it is pointless, and counter productive to put glue on the bottom of the hole.

Some lesser people advise putting a ring of glue around the uppermost edge of the hole or around the leading bit of the rung and let the insertion process spread it to where it will do the most good.

Not me.

If I want the glue to be on the surfaces that are supposed to be together, I put it there. I use a stick to spread a thin coat of glue all around the insides of each hole, and I also put a thin film of glue on the corresponding surface of the rung that goes in. Some excess goes down the hole, and some oozes up around the rung. And I clean it up after the rung goes home.

In order to prevent a frenzy of glue spreading and the ticking clock, I do the glue ceremony step by step, first assembling the rungs to legs in a pattern that makes it easy to work, and still assemble the bottom bits in a calm manner.

Take a look.

See one leg with three rungs applied ready to glue. There is another leg with no rungs at all, another leg with two rungs.

You can't see the other leg but it also has rungs sticking in it.

The reason is simple.  All seven rungs will have one end already glued into place before I even start inserting legs into the seat.

This makes each leg insertion a simple process of applying glue to a few relevant ends and holes. Do this a few times, and put the whole thing together by joining the various sub assemblys.

Folks, it takes more than ten minutes to do a slop job of applying the glue to the right places and then sticking all those parts together before the glue loses its grip, and you begin to lose your grip too.

So do it my way.

It is so superior to a frenzy of eighteen holes to glue with four leg ends and fourteen rung ends with a total 'open time' for most glue of ten minutes or less.

Open time for glue is important. Each glue has an allowable time open to the air before it skins over and needs to be cleaned off because it will not stick right. It is not enough to apply more on top because the skin is still there.

There is another reason to be selective about which glue to use for putting tight fitting pegs into round holes.

Some glue has a very rapid 'grab' where it starts to stick almost right away after pressure is applied. This is not good if the glue grabs while the peg is half way in. You either break the grab (ruining the strength of the ultimate joint) or have a great deal of trouble pulling the danged thing back out to try again.

In doubt about which glue to use? Read the label. If it doesn't tell you? Don't buy or use it.

I like hide glue because it gives a decent amount of open and repositioning time, and is ultimately both stronger than most white glues (yes its true, despite being an ancient formula) and it is gently reversible using heat and moisture.

But it is not suitable for building boats, exterior use, or in damp steamy locations.

In my next blog we will get on to putting the top bits on and a few more secrets from your friendly chair doctor.

And remember that butcher block conversion to a desk blog a while back?

The whole thing is smooth and sensuous to caress despite its rough look.  Here is a snap its happy owner sent me of it in its new home.

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