Intro to measuring tools


Another pro for the fractional caliper is that it can easily measure the diameter of small, circular objects. Trying to measure a diameter with a ruler can be a bit tricky.

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I use digital calipers regularly in my work and find they chew through the button cell batteries like nobody’s-business because they’re never truly off, only the display is. They still record measurements even if they’re not visible. The LCD may be the most power hungry part of the whole apparatus but they still run flat way too quickly. I’d prefer a nice dial set.

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This is about levels:
A crucial point of the tube in which the bubble floats: it must be arched like so (old style spirit level with an arched tube)or gradually tapered (like so: modern spirit level with barrel shaped tube), so that the bubble is in the indicated area only when leveled.

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I used to have a customer with a so-called ‘package printer’ used to print school photo packages (y’know, a 5x7 and two 3 1/2 x 5 prints on one sheet of paper) about twenty-five years ago. I did some repairs/adjustments on these for him.

After this job, he began calling me every few weeks to complain that the 8x10s weren’t quite the right size. I’d go over, adjust the positions of the lenses at no charge and all would be good until a few weeks later, when he’d call back…

After a few return visits, I began to suspect the real source of the prints wandering sizes. I went to a store that supplies precision tools for machine shops and bought a I’m-quite-sure-THIS-one-is-good ruler. I then went to this customer’s lab and gathered all the rulers he had on hand and laid them side by side: their scales all showed different lengths at, say, the 10in mark!

After letting the shock register with my customer for a few seconds, I said: “This stainless steel ruler cost me $35, and THIS is what we’re going to use to determine whether the 8x10s really are 8x10.” After finding the ruler that was closest to the good, expensive ruler, I told him to only use that one to measure. Problem solved."

I love good quality measuring tools.

Edited to add: Vernier scales are such a cool invention. So are pi rulers. Über-cool: my SS pi ruler which has a vernier scale. And a serial number.


Had not used digital calipers before, but the vernier calipers we’ve used in class seem to indicate accuracy to 1/128".

One piece of advice though: if using a vernier caliper make sure you understand how to interpret the scale. The design seems elegant now, but confused me at first.


How accurate do you think laser printers are? I sometimes generate and print a measurement scale to stick at something. (A bit of “plastic spray” overspray makes it fairly durable. Or you can laminate it.) So far it seems the DPIs are as good as advertised.

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I have a printed ruler on my desk at work – I have a very nice metal ruler locked in my desk drawer (it matches one of our “calibrated” rulers). I think that it took a bit of iterative printing, but the paper one is a dead on match for the metal one.

And you can print many other things than just rulers. Program the lines in HTML with absolute positioning, and you can have rulers with arbitrary scales (or even combined scales), paper backgrounds with printed scales for photographing things, and various disposable jigs and cutting templates.

With toner transfer, photoetch, or laser etch, you can even make rulers of arbitrary materials, including metal and glass.

The absolute positioning (with Firefox and div elements with border on one side) works almost perfect. The scales have noticeable jitter at the millimeter marks but there is no stackup of the differences. I think doing it with SVG would be better.

And with rotating of the elements you can even make curved scales, e.g. for analog instruments. Avoid doing these things manually in a drawing program; if you write a code that generates it for you, you can use it over and over with minor variants. It can even calculate and interpolate the positions of marks for you - print a “blank” template with angle marks, mark where the needle points at given values, feed the angles to the program, print a resulting dial.

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I remember now – it was a postscript file that printed the ruler, so I don’t think that I had to do any iterative scaling…
This guy has a few simple examples:
hzeller/postscript-hacks · GitHub

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Depends on the particular model and how worn out the rollers are? I’ll have to test mine!

I would give my right eyeball for a great YouTube video about measuring skills for building. I’ve been doing some remodeling in my kitchen and I truly am terrible at it.

Do it. Laser printers are usually accurate enough for SMD circuitboards without any extra calibration, so it should work for you.

There is a story in the Gnostic Gospels about little boy Jesus coming into his father Joseph’s shop, to find him cursing because he cut a board too short. So Jesus grabbed the end and pulled, and the board was longer.

Yea’ there’s a reason those books aren’t in the Bible.


A ruler, rather than a level, is sometimes better for hanging a picture. You don’t actually want the picture to be level, but instead, be even with the line where the wall meets the ceiling. You want to make sure the left and right side of the picture are the same distance from the ceiling. That will make it look level, regardless of whether it actually is level. You’d be surprised at how many houses don’t have a level ceiling line. Houses really do “settle”.


Another option is to intentionally misalign the pictures, enough to look like artistic intention.

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The thing that worries me is the black box effect - trusting what the digital scale states. I know with my vernier calipers if they meet flush and are not out of square (and you have put down some decent wedge initially - precision costs) they will be a true measurement.

Maybe keep a set of thickness gauges, or anything hard and flat enough to serve as repeatable thickness sample (a piece of glass, for example? The thickness can be arbitrary, it just must be the same all the time at a reasonably workshop-like range of temperatures, and the sides must be pararallel enough to not matter much where you measure and hard enough to not wear, so a glass plate sounds like a suitable thing), to occasionally make sure that the instruments show what they should be showing?

Or maybe use bearing balls, as they come in a range of materials, from pretty hard steel to silicon carbide, and a range of diameters, and are very (enough for this purpose) round?

Not always the best for accuracy (although they do fit the “metal rule” suggestion), but I LOVE a good speed square. They’re really, really useful for making quick, accurate measurements and manipulating wood. Not great if you’re trying to construct a puzzle box, but really useful if you need to make a lot of chops for basic projects or structures.


This post massively undervalues how useful a combination square is. In fact, it really should be on it’s own and separate from a regular fixed square. A combination square acts as as ruler, depth gauge, parallel ruling device, relative dimension measurer as well as others. Most have levels and scribers built in. I use this thing all the time for loads of things.