What size lead do you need?

Our patent pending (not really) super-sophisticated lead measuring system for finding out whether your pencil uses .046" (1.1mm) or .036" (0.9mm) lead: which paper clip fits in the tip, a little one or a big one?

The Most Common Vintage Sizes: .046" and .036"

Prior to the introduction of the Eversharp pencil in 1913, there was no "standard" lead.  However, the Eversharp became so immensely popular, and so widely copied, that by 1916, nearly all standard mechanical pencils adopted the same size as the original:  .046 inches, or roughly 1.1 millimeters.  Just before World War II, Parker and Sheaffer began to use .036 inch leads, which are roughly equivalent to 0.9 millimeters.
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Unless you have one of each for a side by side comparison, telling you that the .036 inch leads are a little smaller isn't very helpful.  If you are in doubt, here's an easy way to tell:  a small paper clip is close to 0.9 mm, while a larger one is just about 1.1 mm.  Bend open one side of the paper clip and insert it through the tip of the pencil to see which fits snugly..  

Clutch pencils versus screw-drive and repeating pencils

You might wonder, in browsing through the various sizes in our "Exotica" series, whether a couple thousandths of an inch really makes a difference.   In the case of a clutch or leadholder style pencil, in which jaws clamp down around the lead to hold it in place, so even if a lead is a bit large or small, the pencil should still function normally.

With screw drive and repeating pencils, however, the tolerances are much more precise.  Each of the pencils at right has been fitted with a specific size of our leads.  Any other size will either drop out or won't fit through the tip.

These pencils, fitted with our leads, accept leads between .072" and .126". Although the range in leads varies by only .05", each of these pencils only accept one specific diameter.

This Pelikan 450 still had a piece of lead in it. A quick check with a micrometer confirms the size is .046.

Determining an unusual size. 

With any luck, you'll have at least a small bit of lead in your pencil to measure with a micrometer; in cases of doubt, that's the best alternative.  Many of the more famous pencils used unusual but standardized sizes, such as Eversharp's "75" (our Mighty "75") and Checking (our .120 inch "Checkmate" series).   As we update the mechanical pencil museum, we'll be noting what sizes the pencils shown take.  If the paper clip test above doesn't help, you don't have a micrometer, there's no scraps of lead remaining to use as a guide, and you can't find an example in the Mechanical Pencil Museum for a direct comparison . .  . just drop us a line and we'll be happy to help..