Saturday, April 13, 2013

The Bits Of Roubo's Plate 11 Bench

As the French Oak Roubo Project trudges forward, excitement builds as the various bits and pieces for the Plate 11 bench begin to emerge.

We've enlisted the expertise of the wood vise screw experts at Lake Erie Toolworks to create the massive French oak leg vise screws, plans for which we pulled directly from plate 11.



There is one issue with plate 11 which caused some head scratching. The threads on the leg vise screw are not rendered with the normal precision of Roubo's work. They are more of an illustration than a "schematic." The thread geometry varies by several degrees along the screw. The pitch of the threads is about 1-1/2 turns-per-inch, which although fast to operate, might be a little too fast for varying holding pressure. Using a 2 tpi wood screw, which provides a good balance of speed and control as a starting point, Nick at Lake Erie suggested we split the difference and try a 1-3/4 tpi pitch.


The result was a screw which would not only function sweetly, but also more closely match the robust threads from plate 11.


Lake Erie will also be cutting the threads for the Roubo screw directly into the bench legs, instead of using a separate nut. This will allow for more vise capacity with the same length screw.




These samples are made from Lake Erie's standard hard maple.

Once Lake Erie has created the screw, we will then fit the hand forged iron parts from blacksmith Peter Ross.

Amazingly, Peter does not use any jigs or forms to make the iron ferrule. Yet it's still a dead-on circle. And by dead-on, I'm talking thousandths of an inch. Remarkable.

Here are some pictures of the ferrule in process, as well as the finished handle and planing stop.

Peter's description of the process:

"Here's a quick series showing making one of the ferrules. first step is to draw the purchased bar stock down to the required size. Then the ends are scarfed and the bar is roughly bent over the horn until the scarfs line up. The joint is forge welded and smoothed. Finally the ferrule is trued over the horn of the anvil. All done freehand, no jigs, etc.Sorry for the pink color, but it was evening and in flourescent light."














4 comments:

  1. Jameel,

    Does Lake Erie cut the external threads with a screw box or on a lathe?

    Did they make a dedicated tap for the internal threads?

    Dan

    ReplyDelete
  2. Dan,

    I don't think they are using a screwbox, although that's how Roubo did it. I'd drop Lake Erie a line if I were you.

    ReplyDelete
  3. Jameel,

    So the screws themselves will also be made out of the French oak? I was under the impression that oak was not well-suited for making screws. Not sure where I got that impression...perhaps I'm wrong?

    ReplyDelete