Friday, January 1, 2010

My Roubo, part 7

(Go back to part 6)

The last step before assembling the base is to attach the hardware for the leg vise screw.


Drilling the pilot holes for the wood screws.


Screwing it down. These are long beefy screws.

The first step in drawbored assembly is to bore peg holes in the side of the mortise. Then insert the tenon and mark the hole positions with a brad point bit. Remove the tenon, re-mark the hole positions 3/32" closer to the shoulder, and bore the holes. When a peg is driven in, it follows the slightly offset path to hold the tenon in place like a spring pin.


Boring the peg holes in a leg.

For these holes, I used my Spofford brace, which I acquired recently from one of the antique shops in Amherst, NH for about $15. It's marked "Fray & Pigg"; according to the Sydnas Sloot page on these braces, Pigg parted company with Fray before 1866, so these markings date it to the period 1859-1865. This tool was made about the time Lincoln was President, during the Civil War. After some 150-odd years, it works like a dream. The cup handle and chuck are dead-on-axis, and the clamshell chuck has a dead-simple positive grip. Except when I need the torque of a brace with a larger throw, this has become my primary tool for boring, light, fast, and easy to handle.


Assembling the first joint. The alignment pin is an individual Sears Craftsman pin for about $9, since they didn't have the Companion set that Chris Schwarz recommends.

As soon as you peg one of these, you realize deep down at the cellular level, this joint is SOLID. My mortise and tenon skills still need a lot of refinement to get a close fit, but this technique makes up for any deficiency as far as structural integrity is concerned. The glue isn't really necessary.


Seems obvious in hindsight, but you should bore the holes for both stretchers before assembling the first one! Otherwise you get into the potentially difficult position of boring into a partially assembled joint with large, awkward pieces.


Boring the offset holes in a stretcher tenon.

I bored and dry-assembled the rest of the base before pegging any more joints, then pegged them all at once. This is the moment of truth. All the little inaccuracies will conspire at this point. But the base went together well, mostly square with no twist to the stretchers.


Trimming the peg ends flush.


The assembled base positioned for tracing around the leg tenons, for mortising the top.


The one most obvious issue that will require some work: the front right leg is slightly out of square in relation to the front stretcher, so there is a gap at the end of this straightedge. This means it will be slightly out of alignment with the top.


Structural test. Result: SOLID!

The next thing will be to mortise the top for attaching the base.

(Continue to part 8)

3 comments:

  1. Are you going to use that alignment pin in your leg vise or is it too thick?

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  2. I actually hadn't thought about that. I got the alignment pin specifically for doing drawboring, so I don't want to tie it up in the leg vise. In the back of my mind I was thinking of just using a screwdriver, or maybe make some simple wooden pin.

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  3. Ah. Good to hear the pin won't be a complicated matter!

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