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Baby Plane Making, part 1

A trustworthy new brass fingerplane will cost you some $50-$70. You need a few different sizes, times two, for flat-bottom and round-bottom. That’s a lot of money.

So make your own out of wood! I love wooden fingerplanes – they are lighter, wooden tools feel nicer in your hand, and they sound a little different from the brass ones.

Here’s what I’ve learned from making my 3 wooden planes. This is a general post, and I’ll go into more detail over the next couple posts.

The type of plane we’re making here is based on the sandwiched Krenov style / crosspin + wedge / whatever you want to call it.wooden finger plane exploded diagram

Ingredients

  1. BLADE. This is your constant. You will build your plane based on the width and thickness of your blade. The sizes we’re working with at school are 3/8″, 1/2″, and 1″ wide, all O2 untempered steel stock that we have to cut, shape, harden and temper ourselves.
  2. BODY WOOD. Something stable and not too soft. Since we are violin makers, maple is plentiful and will do fine (but maybe don’t use that pink streaky low-density stuff we get for our first instrument). Grain orientation for the body is not crucial for tiny planes, but I’ll go into further detail on that in a future post.
  3. SOLE WOOD. If you can manage it, get some quartersawn very hard wood for the sole. Some folks are using bubinga, ipe, ironwood, ebony, rosewood, etc. Most of the dense, tight-grained tropicals are supposed to work well for this, though I did make one out of purpleheart and it turned out to be surprisingly/disappointingly mushy! Keep a little extra of this sole wood for the wedge. Straight grain will make life easier but if it’s interlocking, you’ll live.
  4. CROSS PIN. Use a metal rod of some sort. Make sure you have an appropriate drill bit for it.

Design Considerations

Plane making is really not that difficult. If you haphazardly slap some wood together, chisel out an opening, pin it, and stick a wedge and blade in it, you’ll probably have a functional plane. But if you plan ahead, these little points could make the difference between a plane that functions and a plane you loooove.

 

On any plane, the area right in front of the throat takes the most wear.

throat wear finger plane

You need to find a balance between supporting that area, and having space to relieve wood shavings. On a small plane, the space for chip relief fills up very very fast, especially if you tend to stick your finger in it.

chip jamming finger plane ergonomics

As you redress your plane, the throat will get larger and larger, so consider ways to minimize that. In violin making, finger planes are used for arching, but they do not produce the finished surface, so a tiny throat (which is supposed to reduce tear-out) is not as important as it would be on, say, a smoothing plane. Still, a giant throat on any plane disturbs me… throat opening from redressingFor a small finger plane, if you keep your plane sole reasonably thick, this configuration is my happy medium for achieving a roomy chip receptacle and well-supported throat that will stay somewhat small with each redressing. chip relief strong throatMy finger planes are mostly for arching and/or some edge work, so I’m just sticking with the traditional 45° bed angle, blade bevel down. Low angle is supposedly better for cutting endgrain, high angle is supposedly better for figure.

Cross pin placement should not be mindlessly done. Factoring in blade thickness and wedge shape, you’ll end up a line of acceptable cross pin placement. Again, you’ll have to strike a balance. The lower you place the pin, the better the support near the cutting edge, which should help reduce blade chatter. Don’t go too close though, or your wedge will have less room to do its job without getting in the way of chip flushing.

The wedge pushes up on the pin pretty forcefully, so consider your final shape and make sure you have enough meat above the pin.

Consider how you tend to grip your finger plane. I hold really really tiny tiny planes a little differently from just kinda tiny planes. Consider how the final shape of your plane and your grip on it could affect some of the other design points.

 

 

Next post will be on actual construction.

I’d like to give a little shout out to my friend David Finck, who I met at Oberlin. He is the author of Making & Mastering Wood Planes, which would make an excellent gift for any of your woodworking or luthier plane nerd friends.

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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?!?!

THE ZULAGEN PUZZLE

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!

EXAMPLE

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.

1.

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

zulagen mental rotation planing puzzle 1

2.

Now for the good stuff.

0104 quiz 2

3.

0104 quiz 3

4.

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.