Friday, February 03, 2006

Mechanical Pencil Mechanisms

Without getting too technical, it seems to me that these days there are effectively three different types of mechanical pencil mechanisms, namely:

  • Ratchet – the lead is advanced by a fixed amount every time the mechanism is activated.
  • Screw/slider – the lead is advanced in a continuous manner as the mechanism screws or slides its way down the pencil.
  • Clutch – a set of jaws grip the lead and the mechanism opens and closes the jaws allowing the lead to slide freely.

Well that’s the mechanisms, and then we have the means of activating them. These days there don’t seem to be many variations on the screw/slider and clutch. A twisting top on the pencil usually activates screw/sliders, and a push button top usually activates clutch mechanisms. It’s the ratchet mechanisms that have the variety of activators. So as a generalisation, we can break mechanical pencils into five groups based on their mechanisms.

  1. Push Top Ratchets – this would have to be the most common mechanism by miles. It’s a total guess, but I would expect 90 to 95% or even more of the mechanical pencils manufactured each year would be push top ratchets. They cover all the price ranges and thin to medium leads.
  2. Button Ratchets – a button, lever or similar is located on the side of the pencil (anywhere except the top!) and that is used to activate the mechanism. It seems reserved for lower cost pencils and thin to medium leads.
  3. Twist Ratchet – part of the pencil is twisted to activate the mechanism. Usually the whole top half, but sometimes just a small upper section, and sometimes the whole body. After twisting it then springs backwards to its original position, it does not stay permanently screwed around. It seems most common on mid and upper price range pencils, and thin to medium leads.
  4. Screw/slider – part of the pencil is wound around to advance the lead. This was a common mechanism in yesteryear but now seems reserved for upper price range, thick lead pencils.
  5. Clutch – a push top (or other means) activates the clutch jaws. Again a mechanism that is far less common now than in the past. These days it seems reserved for thick lead pencils across the price range.

That’s all the technical details dealt with, so what are the good and bad points to discuss?

Personally my first contact with mechanical pencils was with clutch pencils. Actually I think they are my least favourite because you generally have to sharpen the lead to get a writing point. Now I quite like sharpening wooden pencils, but I feel one of the attractions of mechanical pencils is that you don’t (or shouldn’t) have to sharpen them. So I’m left with mixed feelings. I am sure this would be completely different if I was artistic and using it as a sketch pencil where I wanted a good thick lead. Indeed that’s often what the current clutch pencils are advertised as – “sketch” pencils – but I’m not using them for that. On the positive side, you get to use virtually all of the lead as the jaws can grip down to the last few millimetres.

Button ratchets are probably my least favourite mechanism. I always feel that they are somehow going to get in the way of where I want to hold the pencil, or get inadvertently activated when I put the pencil down, or something! They just strike me as wrong. It’s irrational, but it’s the way I feel. To be honest I never really liked twist ratchets all that much, but they have really grown on me over the years and now I quite like them. You can generally operate most of them one-handed. Last of the ratchets is the push top, the most common of all mechanisms, and rightly so. The push top is easy to activate one-handed, but it does have its drawbacks. Most push tops are refilled by removing the top button, and many also have an eraser under there. When you push the button back on you invariably activate the mechanism, which may not be what you wanted to do. Ratchet pencils usually take standard 60mm long leads and the mechanism can’t hold the last 13 – 15mm of lead. That’s a lot of wastage. Basically 25% of your lead is thrown away! Think of all the words you could have written, the doodles you could have drawn – it’s an outrage!

Last but not least then is the screw/slider mechanism. I don’t really know too much about these, as I only have a couple of pencils that use this. They are a bit of an effort to reload – each lead has to be fitted to the mechanism, there is no automatic loading of a new lead from the spares inside the body. But at least like a clutch mechanism you get to use virtually the entire length of the lead.

Footnote: Original draft prepared with Faber-Castell Grip 2011 0.7 mechanical pencil.


Anonymous said...

Interesting info. One system you list actually has a number of variations. The screw/slider mechanism is the most common variety in vintage pencils, but its much more interesting than just a 'screw slider'. What is usually found today is the 'propel/repel/expel' design. The lead goes in or out, and when you twist it so it goes all the way out, a part of the mechanism pushes the lead out of the little sleeve that holds it.
Before this was invented, there was the propel/repel, and the original mechanical pencil, made famous by Eversharp, was propel only. the lead, in short one inch lengths, is loaded from the top, like a ratchet or clutch design, and the lead is pushed through a very tight opening. It holds the lead tight, but its a one way trip for the lead. But the tight hold made it useful for drafting. Today, Autopoint makes a version of this mechanism, and you can buy it online from Autopoint themselves. And today, the propel/repel/expel is generally used in high end pencils, but an excellent example is the faber castell E-motion pencil, with a 1.4mm lead. The plastic one is avaible at between $15 to $20 US.

Kiwi-d said...

Thanks for the extra details, "anonymous". I don't actually have an FC Emotion although I think I will be curing that deficiency soon. Guess I'll have to get an Autopoint too, which I am only vaguely familiar with. Just another of the many, many brands not available in my part of the world. I guess Eversharp used to try and make a selling point of the expel only mechanism by going on about the sleeve cutting "rifling", etc.

Anonymous said...

Could you review
>Pilot G-2 07 mechanical pencil