This looks like a perfectly normal mechanical pencil.

But it actually has a lot of interesting engineering to solve one frustrating thing.

Broken lead.

This is the Zebra Delguard.

The unbreakable lead pencil.

Unbreakable Pencil

During typical operation it works and feels like any normal mechanical pencil, but if you’re a heavy writer who applies too much pressure on your lead tip, that’s where the Delguard protective mechanism kicks in to prevent the lead from breaking. But let’s take a closer look. Pressing down firmly on the lead at an angle and you’ll see the sleeve tip extends out to protect the lead. Or if you press down vertically on the lead it will auto retract inside again protecting the lead from breaking. It’s the combination of these two mechanisms that makes it almost impossible to break the lead no matter how much pressure I put on it.


Opening up the pencil give us a better idea on how it works.

This is the chuck, it’s the part of the pencil that dispenses and holds the lead in place and makes that clicky noise when you press on the cap. But what’s special in this case is the suspension of the chuck. On this pencil the chuck is held in place by a spring that allows it to move around freely from the rest of the pencil. With enough pressure the spring will compress and push deeper inside the case. But it also has a lot of flexibility to bend off axis from the rest of the body when you press on the lead at an angle.

pencil chuck

The next part to look at is the sleeve or guard of the lead pencil.

And this part is designed to extend out and shield the lead when you press down on it at an angle.

The sleeve is held in place by a spring but when you pull it out you can see that the sleeve isn’t cylindrical but instead curved like a spinning top. So when you apply a perpendicular force to the sleeve, the curved shape causes it to extend out and shield the lead from breaking. This dual spring design makes it almost impossible to break the lead on your pencil from pressure alone.

dual spring

But it does have some limitation.

The DelGuard pencil comes with the warning: Lead may break when retracting the lead more than 3 times or using a softer lead. And this makes sense because the guard system is only designed to extend out so far. So any part of the lead that extends past the range of guard just can’t be protected.

So that’s the Zebra Delguard mechanical pencil.

A pretty cool feat of engineering to solve the problem of lead breaking for heavy handed writers. But if you don’t have an issue with breaking your lead, it feel just like any normal lightweight mechanical pencil. In that case, maybe check out the Uni Kuru Toga. Another pretty nifty piece of pencil engineering.

But hope you guys enjoyed this one.


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