“thaMographe” Review

I’m not sure where I’ve been for the last five years or so, but I’ve recently discovered a cool tool called the ‘thaMographe’, invented by Thierry Delattre. It looks like this:


It’s a small tool and the inventor claims it can conveniently replace a compass / set square / protractor / ruler. An all in one tool a bit like a swiss army knife but for maths.

Anyone who has taught constructions at school will be familiar with the typical frustrations that come about regardless of how well you plan for them: super loose compasses, students jabbing each other, compasses with the pencil fastener missing, students getting cross because their compass slips as they’re drawing a circle, or they wobble it as they try to figure out how to manoevre their hand 360 degrees around their other hand. It’s a tough unit of work, if only because of the frustrating elements of the equipment we use. And so I was pretty excited to find what could be a solution to all this – not to mention a possible money saver for schools.

I’ve been using one for three days now and I’m really impressed with how easy it is to use. The video below demonstrates the basics:

You’ll notice that a key feature of the tool is the central line, which enables quick and easy drawing of shapes and angles, without lifting the pencil from the paper. Pretty innovative stuff!

*edit*: I found this other video which demonstrates the capabilities in a little more detail:

I managed all of the typical compass requirements for a ‘school task’ easily:

The only struggle I had for these is that I was using a pad with a ring-binding – which meant that as I swung the tool around, it sometimes got stuck and couldn’t get past. Whoops. So don’t use ring-bound pads! Again, this wouldn’t affect a school student I imagine. I did wonder if it would get stuck on the central binding of an exercise book, but I tried it with a couple and it got past quite easily with a little prodding. I’m not sure this would even be a likely scenario in many schools as lots use individual pieces of paper rather than squared exercise book paper for constructions work.

You may have noticed that the tool has individual holes that are set such that you can adjust the radius of a circle by the millimetre, so there’s almost no loss of ability to resize the circle with a radius of between 10 and 110mm. The nice rubber segment where you place your finger as the compass ‘point’ is comfortable to use and very easy to push down and hold the tool in place. It has never slipped in all the times I have used it. It’s also easy to put a standard pencil in the holes, although it needs to be pretty sharp. If you want to use a pen you really need a a fineliner.

What was really nice was that you can happily stop and start any arcs or circles and you don’t get any wobbles or double lines in your diagram. It’s also really easy to swap fingers around when you get most of the way around a circle, and it doesn’t ‘upset’ the diagram. This is a great advantage over the traditional compass, especially for schools.

In summary, for schools, the advantages are pretty clear – it’s only one tool instead of several, it doesn’t have sharp bits, it doesn’t get ‘loose’ in the way compasses do, it doesn’t slip, and it does all the things required from the UK curriculum very easily. I would prefer to have them in my department rather than a myriad of protractors, rulers compasses. I don’t know if they’d save you money overall, as I don’t know the current cost of a class set of rulers / protractors / compasses, and I doubt many schools stock class sets of set squares. Either way, they are available with discounts for bulk purchases here:

Buy From Tarquin

As a massive geometry geek, I thought I’d try out a few more advanced things with it, to see if it could replace a compass for what I use them for… I suspected the accuracy of a compass was going to win overall, and I was right.

I tried a little quadrature of a rectangle first:


I was happy with the result. Not perfect, but that’s more me than the tool. So far so good.

Then the ultimate test, this tricky Islamic Art style thing:


You can see I was far less successful with this one! Where three circles are supposed to overlap on one point, they often miss a bit. This was largely because I struggled to line up intersecting lines with the little cross on the tool, compared to just sticking a compass needle on it.

Here’s a compass version:


Now in fairness, I’ve used a compass a LOT more than I’ve used this new tool, and I tried again the following day with much better results. This time I was a little more strategic and lined up not only where the cross should go, but also checked that the pen lined up with all the intersections before just blindly drawing it from the cross. The result was much better:


But I still felt a needle was easier.So while I will definitely put this tool in the back envelope of my notebook (another handy advantage!), I don’t think I will be throwing away my compass just yet.

Either way, I’m pretty sure this tool is NOT designed to replace a compass for more advanced geometry, and it of course has limitations.  It’s designed to replace 4 school tools with one, and it does that, in my opinion, very well. Two thumbs up.