“I never knew who I was talking to. I was always worried about the physics. If the idea looked lousy, I said it looked lousy. If it looked good, I said it looked good. Simple proposition. I've always lived my life that way. It's nice, it's pleasant - if you can do it. I'm lucky in my life that I can do this.”
Richard Feynman

Surely You're Joking Mr. Feynman

Kumiko Unfolding – Part8: Jigs for Lamp Frames


I was content with the overall design of the small lamp. However, I felt that making the frame took way too much time and delicate manual work. The lamp frames were supposed to be a canvas for Kumiko patterns. I didn’t want to spend 80% of my time producing them. I wondered if, given the tools I have, there was a way to more efficiently make the lamp frame.

Having built two lamps (one large and one small) I had a clearer understanding of the tasks I needed to be done with the help of jigs. I also had specific dimensions that I wanted to work with. Having specific dimensions meant I could think about specific jig dimensions (jigs that are adjustable are much more complicated to create). I imagined a set of three jigs that I felt I could produce that together would make it easier for me to produce better lamp frames … and set out on a journey that took over a week to complete.

Jig1: Mortises

This entire jig is basically a substitute for a drill-press or Mortiser (tools I don’t have). It is intended to create a hole which will become the mortise (hole part of the joint) in a mortise and tenon joint:

By GreyCat – self-made SVG, loosely based on idea of work Image:Mortise_and_Tenon.png by Luigi Zanasi, CC BY-SA 3.0, Link

The base of the jig is intended to hold a piece of the frame using a twisted clamping mechanism:

The top part is indexed using the pins in the base and is sized to hold a router (which I do have):

Then the piece to receive the mortise is inserted (and clamped) from one side and a second piece, inserted from the other side, acts as a stop – making it possible to easily repeat the mortise in multiple pieces:

The router is placed on and used as a drill:

A depth stop on the router allows me to go to the same depth repeatedly … and it produce decent results (clamping is not as tight as I would like it to be):

During this exploration Litsa selected her favorite place in the workshop – right under the end of the vise … apparently fresh shavings are the best:

Jig2: Tenons

The second jig is designed to make precise and repeatable tenons in batches (aiming for 8 pieces at a time). It too is made of a base with a stop and indexing pins:

… and a top which also holds the router but allows it to slide along the guides:

You can see the cut it makes after the first test rung:

Now when I add in the frame pieces, run the router, rotate … repeat 4 times:

I get this:

I can finely adjust the size of the tenon by adjusting the depth of cut on the router.

At this point you may be thinking “square peg – round hole” … and you would be right. My intention was to use a chisel to square the round holes. After trying that I created this small guide which I can clamp onto the piece and quickly make straight repeatable cuts:

… and to my surprise it worked well … however having put it to use I intend to try rounding the pegs instead of straightening the hole!

Jig 3: Rabbeting

The 3rd jig is for creating a rabbet (into which I will be able to set the kumiko panels more esthetically and reliably) – this replaces a router-table (which I don’t have) but utilizes the router (which I do have).

The base is again a surface with a stop (along which the router can run) and indexing pins (for aligning the top part):

The top part overlaps the stop by a few millimeters:

… and in between them sits the work-piece:

The part of the work-piece that extend beyond the top-plate will be routed off; the part underneath the top-plate will remain in-tact. I use another clamped sacrificial piece to keep the work-piece in place:

The router bit that runs along the edge of the top plate and routes off material to whatever depth the router is set to:

And in the case of the lamp frame I end with pieces that have this profile:

… with the ability to produce quick, fairly precise and repeatable results:

I also added stop-blocks to assist me in creating partial rabbets:

like these:

Kiwi, at the time a new arrival at Bhudeva, also found a comfortable niche in the workshop:

… and then it was time to see how it all comes together:

With great(er) ease and precision I was able to create two small lamp frames.

I was not so fortunate in making Kumiko strips to populate the lamps. I thought I had this part down but the bandsaw performance changed drastically … namely, it started drifting … unpredictably. Drifting is when pressures released from the wood during the cutting force the blade to one side and away from a straight line cut. This video explains drift and sheds some interesting light on using a bandsaw for resawing:

I’ve since learned that using the bandsaw is not as obvious as it seems and that the form and quality of the blade itself is very important. I’ve discovered a couple of technique-tips that partially mitigate some of the problems. It is likely that an average-at-best blade came with the saw and that it performed much better when it was new, but may have quickly lost some of its literal edge. After quite some hunting and waiting for a replacement, a new blade has arrived but I’ve been to busy with other construction works at Bhudeva to try it out.

I was able to extract (from my failed cutting attempts) just enough Kumiko strips to populate one of the lamps with a new pattern and so another small lamp is completed:

During this round I also placed more attention on the light-bulb holder. A simple thing that had required more refinement that I expected. It needed to:

  • Hold the E14 lamp holder I was able to find.
  • Be low enough in the lamp to fill it with light and avoid a dark spot at the bottom.
  • Be high enough so as not to stick out the bottom.
  • Be removable (in case the bulb needs to be changed).
  • Have a place for a wire to enter and connect to the holder leads.
  • Be closed off at the bottom to protect from any exposed wiring.

These were a lot of demands for something that seemed simple. I ended up with this shape:

It is hollowed out using a succession of drill sizes. Wire can enter the closed chamber from the bottom and the bulb holder sits snugly on top:

The small clipped corners make it possible to twist it in and out of two “rails” which are permanently attached to the base of the frame:

… and that’s as far as I have gotten!

When I have some time I will try the new bandsaw blade and see how it performs. Aside from that, I am left with the challenge of milling wood – converting the raw lumber into straight and dimensioned workpieces. This is a general need in the wood workshop (that I’ve avoided so far by only doing rough work) … but now it specifically pertains to both for the frame pieces and Kumiko strips … and there is no way around it.

It seems that milling will require move investment in machinery. There are numerous options – from cheap, to mid-priced but incomplete and through to expensive and complicated to execute (remember I still don’t have a flat floor in the workshop!). I’ve done most of the research and I am at another investment junction that I do not have the capacity to resolve for now.

So feeling both content that I got this far … and stuck!

This entry was posted in inside, Kumiko. You are welcome to add your comment

Leave a Reply