Martin-IT

breadboard ? how to cut the deep mortise ? drawbore ?

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Hi,

I experimented with my 1st breadboard at the end of a table.

1st: I used a mortiser to cut a deep mortise, that was long process.... any shortcut ? ..or just practice by patience ?

2nd: I tried also to do a drawbore, but the bottom of the breadboard, more or else split in all direction instead of pulling the join tight (after the painful time doing the mortise). Most likely, my offset was too much ?

 

 

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Drop-cut slot on the router table is my usual method.  Determine the bits final height then lower it X number of turns to leave it 1/8" proud.  Put stops on the router table fence for the starting and ending positions of the material.  Drop at starting position and make the first pass then lift off. raise bit a couple of turns and run the material again.  Repeat till full depth is accomplished.

Similar process here:

335198529_19-GUS-longmort-1.jpg.c4b7698f7e89a831841f352a7f477034.jpg

57b875143d8d6_20-GUS-longmort-2.jpg.307f43a1f92ddc35e686116ae7047665.jpg

Not a big fan of draw-bore.  Probably a west-coast, minor-humidity-swing thing :)

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You could also do it with a plunge router.  Just temporarily attach a board on each side of the work piece as support.

As for the draw-bore, the offset should be a max of 1/16" and I like even less.

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2 hours ago, gee-dub said:

Not a big fan of draw-bore.  Probably a west-coast, minor-humidity-swing thing

Me too! But I have made many bread board applications. Some very wide. No failures. And no draw-bore. In high humidity.

My speculation. The draw-bore joint probably has been around for more than 100 years. Maybe a lot more. Franklyn Titebond aliphatic resin was sold to the public in the late 50's or 60's. But the draw-bore stays popular. I called Frasnklyn and spoke to technical support. Found out that titebond allows creep. that  is what they called it. On my bread boards most are not exactly even as the body clearly moves. And titebond allows it. A very favorable characteristic for wood working. They also said that titebond is not allowed in structural like a wooden I beam. There you want and is required not to move at all. I think like epoxy. And that is why I don't need draw-bore. I just put my thumb to the edge of my oak bread board desk top. We are just slowly turning off the AC (South Florida) so the wood is very dry. The end board is about 1/32" longer.Not bad. About 12 years old. Always kiln dried is what I use. I currently use the dominoes for bread boarding. And I have used several other methods. All worked fine. The dominos I think are the fastest.

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I've pulled many very old drawborn pins out of different things.  Using dry lumber, and modern clamps, I never use them.  All the old ones I see have taken a permanent bend, so it looks like to me that they had done what they were going to do when the piece was put together.

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I have even done the drop-cut method on tge table saw. Ends of the mortise have a radius, so I cut radii on the tenon ( full width, full depth). I used drawbores for appearance more that structure, offset less than 1/32 in walnut, they are working quite well.

If your breadboard cracked radially when driving in the pegs, I'd suspect they were too large for the hole. Too much offset crushes the grain where the breadboard meets the tenon shoulder.

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I cheated on my last breadboard ends - I clamped the ends tight and then thru drilled and plugged the holes.  Not as strong as a good drawbore, though.

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At the other end of the table, I cheated also,. I put glue at the center of the breadboard, clamp it, then simply drilled the hole. I was wondering also, if the breadboard wall were too thin, about 3/8 to be able to sustain the bottom/side stress.

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