Let's Make Robots!

Need Metric Person to Measure A Pencil For Me.

Are there metric pencils?

If there is someone out there in the Metric World that has a set of calipers, I would really appreciate it if you could measure a pencil for me. Just a regular pencil, the most common one you would find in your particular country. Please measure from point-to-point or corner-to-corner to get the widest part of the hexagonal. Do not measure flat to flat.

I could really use the measurement to the 1000th (ie .000) and I would take it in either SAE or CM. Oh, and I would be curious as to where you are too. 

I just need to know if a pencil is a pencil or if possibly pencils are regulated in some way and thus, vary in dia. from country to country. Maybe there is just one giant factory that makes all the pencils for the whole world. I dunno...

This is not a joke.

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I have three real pencils (not technical)

One is round

Number 1  - 7.75mm  slightly oval 7.64mm at its narrowest.

Two are hexagonal

Number 2 - 7.54mm corner to corner - about 7.03 flat to flat (varies a bit between pairs)

Number 3 (Staples brand) - 7.65mm corner to corner - about 6.96 - 7.05 flat to flat

Dr. Iguana

"The perimeter of a regular hexagon of side length t\,\! is 6t\,\!, its maximal diameter 2t\,\!, and its minimal diameter d = t\sqrt{3}\,\!." (wikipedia)

My sample of (1) pencils consistently shows a diameter of d=7.0 mm (measured across each of the six flat sides).

That translates to a side length t=4.0415 mm and a maximum diameter of 8.083 mm.

Such is true only IF and WHEN a pencil section would be a perfect hexagon. But the corners are soft and slightly rounded. When I set my callipers to 7.7 mm, I can easily rotate my pencil in its grip.

For a smooth slide along a round hole through a plate of considerable thickness, I would suggest 7.8 mm as a minimum diameter for that hole. And when in doubt: lotsa lube!

Here's one from Australia 


If image not attached then it's 7.31mm

I would be thinking in sharpie-Consistant size due to manufacturing technique, and a polethra(?spelling) of colors.......

Mr drawing bot could even be multicolor.......

Or.....I might just be way off on this?

And it seems we have pencil unity in the world.

I am measuring a "regular" pencil on this side of the pond at 7.62mm or .3005". It seems that a pencil is indeed a pencil with probably just some variations due to manufacturing. Perfect! This is not only good news for my project, but I feel it can truly be used as a bonding moment --and should be.

Ah yes, I think back to MacGyver episode 12, season 6, "Jerico Games" (as I think anyone would...) and I remember this quote:

Nikolai: What they told us about American before glasnost, about how all of you are selfish monsters, is totally bogus.
MacGyver: Well, I guess dudes are dudes all over the world.


Thanks guys.

The 2 pencils sitting on my desk are:

Yellow "Dixon" pencil = 7.27mm

Round "Generic" pencil = 8.10mm

7.3mm here in Canada, yellow pencil with eraser at one end, made in China. You need to get one of those cheap electronic calipers my friend... http://www.dealextreme.com/p/digital-150mm-caliper-2306

I have a pair just not at university I have it at home....

A normal yellow 6 sided Danish pencil: 7.6mm

A blue one were 7.45mm

But it seems that round ones are quite popular too: 7.3mm to 7.4mm


Sorry don't have my calipers at university but this might be useful:


My guess is they are mostly made in China and your spec will vary according to how good the quality control was on a particular batch that was imported. Measurements to the 1000th will probably be unreliable as this is not a critical dimension and Chinese manufactures will not reject a yield based on it.

Don't know if this matters for you but you should also consider the type of wood. Not all pencils are the smooth yellow laminate we get here in North America. I remember as a kid in Russia a soft white/beige wood was often with a rough finish and it was much softer than what we usually get here.