Thursday, July 3, 2008

The New Method 2

Here is the beginning of the photo essay on the new marking and drilling method that I have been using. I can honestly say that I've never had such ease and accuracy legging up, or getting a room full of folks to leg up. The idea behind it is simple. Instead of trying to pull a reference off of the leg, I use a premade angle block to impose the reference on the leg. Then by using this new reference and the same block, I can drill the mortise dead on.

Here's how the marking goes.

Start by noting the height on each of the legs where the stretcher enters. Then orient the legs in the seat and use string and rubberbands to connect the two marks.

By pulling the string ends straight towards each other, the string will self center and when you release the rubberbands, they will put the string directly on the center of the leg as it faces the other. Mark these spots, they are where you'll drill.

The next step is to mount a straight edge across the two legs with spring clamps parallel to the string. By moving your head up and down, you will be able to see when the straight edge eclipses the string. If it touches one end first, it isn't parallel.

Then take the block you've cut with an angle that is a good guess at the average angles for the chair (78 ot 79 degrees should be good for most) and place it in front of the leg on the straight edge. I like to put tape on the leg for clarity and easy removal of the line.

Next, mark the angle from the block onto the leg. It is important to stay true to the side of the block. The carpenters pencil works great because the flat on the pencil rides on the flat of the block. Don't try to mark the crotch where the block and leg meet, because it only touches in a small area. Think of it more like scribing a line from the flat block.

Here you can see the mark as it sits on the leg. Obviously, it isn't in line with the axis of the leg, but it won't matter. The mark is the new axis. I came up with this method when having to drill into curved parts where there was no axis, so I made one. In the next post, I'll show how to use this new axis and the block to drill the mortise.

No comments: