The main difference between these leads and wooden pencil leads is that a polymer replaced the clay as a binder for added strength.Īs you can see from the diagram above, it shows how the silicon polymers give their Pentel AIN STEIN Lead its added strength. These Pencils had a new type of lead called Super High Polymer Lead. This changed in 1962 when Pentel launched two new mechanical pencils with 0.7 mm and 0.5 mm lead diameters. To compensate for the lead not being very strong, the lead diameter of the first mechanical pencils was around 0.9 mm. The lead is also bonded with glue to the pencil protective outer wooden case to add strength and prevent breakages in a wooden pencil. The downside of this type of lead is that it is not very strong, but it does not matter too much as it is significant in diameter (approximately 2 mm).
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