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

Calculate spindle speed using absolute pitch!

Note: if you hate math, skip this post.

This is how I looked during a 12+ minute cycle on the mill:

long cycle cnc boredom

So, what better way to entertain myself than to guess the spindle speed based on the MERRRRRP pitch??

You can play along too!

Here’s what I had to work with:

1110 rpm 2

Mary Jane is working on the mill in a factory. She hears an E pitch three octaves below concert pitch A. Knowing that the pitch is created by a tool spinning at a certain speed, and knowing that concert pitch A is 440Hz, how fast is the tool spinning in rpm (rotations per minute)?

Easy peasy! But I have not taken a math class since senior year of high school, over 10 years ago. Granted, the last math class I took was multivariable calculus… so I have a decently developed conceptual grasp of math, but I’m very horribly out of practice. When you’re done solving the problem, scroll down to see how my poor brain stumbled through.

1110 rpm 3

1110 rpm 5

1110 rpm 4

Only 9 rpm off! Enough to break a tap, sure, but still! That might have been the most gratifying use of absolute pitch in the history of MJ.