Friday, December 23, 2011

Mix and Match (V)

Managed to get a bit more done on this joinery project, a little addition to our household. Previous posts in this thread can be found by way of the 'blog archive' links section to the right of the page.

Next up in the process was a little mortising, with an emphasis on the word little. The smallest hollow chisel mortising bit I have is 1/4", and that was far too big for this task. I wanted to make 1/8" (3mm) peg mortises, and cutting a square hole that small was problematic even in light of the fairly extensive set of chisels I have on hand. While I have 1mm and 3mm chisels, they are tall in height and that means they can't get very far into a 1/8" size hole. If I did such small mortises regularly, I would get some custom chisels made, but in this case it is time to improvise I guess. First I marked out the mortises:


The knife marks are slightly inside their marks - they're there mostly to prevent any tear out while drilling. Then over to the drill press with a 1/64" undersize brad point drill bit (7/64" that is), a fence, and a packing piece to prevent blowout from the drill poking down inside the mortise:


I chose a wood even denser and stiffer than Jatoba for the pegs, a wood also from South America - Gonçalo Alves:


If I might be pedantic for a moment, the little squiggly mark under the 'c' in Gonçalo (called a cedilla) means the letter is to be pronounced like 'sah', not 'cah'.

With the mortises roughed out by drill, I used a square jeweler's file to transform their shape:


I filed until the peg was a snug sliding fit:


That's one down and seven to go.

This mini-me mortising was a fairly tedious job and took close to two hours to complete - the Jatoba was no picnic to file, especially on the end grain surfaces:


Thanks John for the use of your file!!

Then the panel tenons required mortising for the little pegs - these are elongated to allow for a bit of movement:


In case you're wondering, the mortises for the panel tenons are widened slightly to allow said tenons to move side to side a little. In my experience, with careful selection of material and grain for the panels, there is not much movement to worry about using mitered breadboard ends. Also, it's the dry time of year so the panels are likely at their narrowest, and the service environment for this piece is one which will limit humidity to a certain extent. Probably the potential for swelling is somewhat minimized. The Jatoba panel is pure vertical grain -- in short, I'm not anticipating much in the way of movement in service.

Next operation involved the Ipe stretchers, the same ones with the quintuple tenons. I used a kama kebiki to strike some lines for the mortises:


Then it was over to the hollow chisel mortiser, where I, uh, took the plunge:


The mortise is roughed out:


The two strechers, looking at the inside faces, mortising for the 1/4" x 1/2" tenons now complete:


Since the stretchers are essentially beams, I took care to locate the mortises close to the central axis of the pieces away from areas of tension or compression. While the loads on these 'beams' are trivial, the structural principle still guides the design.

Some more marking out with a knife was in order:


Then some rough chopping:



Followed by some paring:


A mostly complete squinted abutment, as they are termed:


The sidewalls of the mortise are a bit tight at this point and will be trimmed back slightly. The word squinted, by the way, means 'oblique', or 'sloped'. It's a wonderfully festive holiday word you can try to spring on unsuspecting relatives just as they are slicing into the turkey or wildebeest.

The two stretchers have all their mortises now roughed out. Final paring will wait until the cross pieces are fitted:


Next up are the cross pieces, and for a look at that, you'll have to come back for the next post. Thanks for visiting and as always, comments are welcome. ➸ on to post 6

2 comments:

  1. Chris,
    Well executed small mortices. What cut # is the square needle file?
    Jack

    ReplyDelete
  2. Jack,

    thanks for your comment. I don't recall any numbers written on the files or the package they came in, but I'll take another look.

    ~C

    ReplyDelete

All comments are moderated, so if you're planning to spam this, know now that your clicking and pasting is in vain. I do read the comments before posting, so your mission is doomed from the outset. All this time and effort trying to put your inane spam onto blogs -- is this how you want to spend your time on earth?

Please do me the courtesy of appending your name to your comment, even if posting under the 'anonymous' option. No name = deleted.

Comments NOT accepted include:

-those containing links unrelated to blog content
-spam of any kind, or ham for that matter
-did I mention that attempted spam postings will be non-starters?