Zulagen hurts my brain

Hey kids! Winter break’s over, so here’s a puzzle to thaw out your brain.

You know those mental rotation exercises that are all like this:

Mental rotation exercise puzzle with Beijing's CCTV tower

Well today I give you a violin maker’s variation on that exercise.

I almost broke my brain making zulagens. Zulagens are little helpers that redirect clamping force to where you want for glue-ups. Here, a page out of my notes to explain how it’s used:

0104 zulagen

This zulagen pushes on the ends of the C-bout ribs, and the serrated face reduces slip during clamping. It’s important for the two sides that push the ribs to be squared up nicely. Before you serrate the face, this is what you want:

0104 quiz 1

No light passing through the inside edges of your square.

But this ain’t your regular blocky block! The square reads diagonally across the reference surface (labeled “DOWN”). Sure, you can just flatten your DOWN surface and then square up each angled face individually, but why make it so easy when you can make it WAY HARDER THAN YOU NEED TO?!?!


Turn on your planing brain, it’s time to figure out how to square up the two angled faces with minimal planing.

Based on the light passing under the edge of the square, where should you remove material if you wanna get the job done in one go? Each question has ONE SINGLE ANSWER ONLY!


Let’s do the first one together:

0104 quiz B

The face on the right is fine and good, so the answer has to be A or B. The other answers would affect the squareness of the right face (Remember? Square goes diagonal on reference surface). The left face is reading bigger than 90, so you want to decrease the angle. The right answer is B.

Okay, you’re on your own now. Hover over the image for the answer. Remember, pick only one.


Get warmed up with this one, which is similar to the example.

zulagen mental rotation planing puzzle 1


Now for the good stuff.

0104 quiz 2


0104 quiz 3


0104 quiz 4

So, how’d you do? Comment below if you want to brag (or whimper, or correct me, or point out some technicality that invalidates the whole thing).

And now, circularity for closure.

escher cctv tower


Handcrafted violin maker by day, CNC operator by night

handmade purism vs precision in machining

So this week, I began evening classes at Symbol Training to learn how to operate CNC machines. Quite the opposite end of the spectrum from violin making school, where I am not even allowed to touch the bandsaw. I don’t specifically know what I intend to do with all this training in architecture/design, fine woodworking, and CNC, but it sounds like a good combo for making something really awesome one day. Maybe. But pshh, do I really have to pick a side anyway?? I didn’t think so.

And now, some photographic proof to corroborate the claims made in above illustrations:

graduated spruce plate
This is my spruce plate after it was attacked by a fleet of little round-bottom finger planes. It is about .2mm away from final dimensions here, and I will scrape it to achieve the final thickness.

reading spruce plate thickness with light
It’s unsettling at first, but quite a bit of light passes through that piece of spruce as it approaches final thickness. Take that, Alice Tully Hall!

aluminum cut-off from first day of cnc shop class
This coin, which I cut off from a cylindrical stock of aluminum spinning in the lathe (Manual Direct Input! T02 S1500 M03! Insert! Hand jog, .001, x-axis!), is my token of inauguration into the world of CNC machining. What in the world have I gotten myself into??