Sunday, June 21, 2015

drawbored breadboard ends, step-by-step

If you saw my earlier post, "extrapolating myself into unknown territory", you might be curious if my experiment with drawbored breadboard ends actually worked out. So far, it seems to have. If it explodes in the future, I'll mention it here.

I photographed to entire process to share. More info about this project is available by using the "purple_bar" tag.

This process starts after the joinery has already been cut, which means 5 haunched tenons and mortises in a groove to match. I've already drilled 3/16" holes (one for each mortise/tenon) in the yellow board on the drill press before where the photos pick up the process.

First, I tap the breadboard end in place.

Using the same brad-point bit I drilled the hole with, I make a mark in the tenons. One light tap is perfect. Deep marks will interfere with subsequent steps.

I removed the mortised-board carefully using this slender pry bar. This takes a little time to do without damage, but it's easy with a nearly-sharp pry bar.

Finding the marks can be difficult, but holding the end piece up next to it helps show where to look.

The original mark has been highlighted with white pencil. Here, I made a new mark, offset towards the tenon shoulder. This is the crucial step for drawboring. The offset is about 1/16" in this case.
Drilling holes, following the new marks. For a relatively clean exit-hole, spin the sharp brad-point fast, and push down gently. These are 3/16" holes, using the same bit as I used for the yellow end-piece. Eyeballing vertical is good enough. 
Here, I'm using one of these WoodTek bits that are meant to cut sideways. First I get it spinning fast in the eggbeater drill. I didn't do this to the center hole, which can stay round.
With the bit spinning, I tilted it back and forth. I Leaned over further on the holes further from the center hole, so those will be wider slots. This method provides lots of leverage, but one must tilt slowly to avoid jamming the bit.
Now, back to vertical. I push sideways in each direction to finish making the slot. These slots are the crucial step for breadboard ends, so humidity changes don't ruin the project later.

Don' forget to brush away the chips! It sounds stupid, but missing this step would cause big problems. 

Next I tap the end piece back into place, using the center hole for horizontal alignment, since it is still a circle. These holes will not fully align in the other dimension though, so the peg can pull it tight.

Easing the offset holes with drawbore pins. Nail sets also work for these small holes (both shown). A little push and twist from each direction is all it takes. I might be able to get away with skipping this step, but I'd rather not find out the hard way I can't.

Next I prepare the pegs by rubbing paraffin on them. Not necessary, but an effort-saver. These pegs were formed earlier by pounding purpleheart through a dowel plate. Note the slight taper on the left end.
Driving those pegs home! That blur is my hammer. The tapered tip snakes through the offset holes and pulls the joint tight. It should hold well for a long time, and without glue.
For a minute, I forgot to flush cut the pegs on the bottom.
After a little surface prep, I am satisfied with the way this looks.

This is starting to look like a bar!
Bartender's view.

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