How To Choose Ejector Pins For Injection Molding

The lowly ejector pin for injection mold making just doesn’t get the credit that it deserves. No matter how well the rest of the mold is made, if the ejector pins flash or are the wrong length and contour the plastic part will be rejected. That is why choosing the right pin for the job is important. Saving money on poor quality injection mold components just does not make sense in the long run.

Ejector Pins For Injection Molding
Ejector pins

You might think that the ejector pin is sort of an afterthought; do not be mistaken. It is just as important as the molding details, in fact, it is one.

Types of ejector pins

Basically, there are only three types of ejector pins commonly used in plastic injection molding applications.

  1. Thru-hard pins. As the name implies, these pins are heat-treated to be thoroughly hardened. Obviously, you won’t be drilling and tapping any holes in these pins! They are great all purpose pins with a hardness of 58-62 RC. They are made of either M-2 or H-13 tool steel. They can be used for most molds, up to 400°F, or 200°C
  2. Case hardened pins. These pins are nitrited to 65-72 RC and are also great for general use. They perform well at temperatures above 400°F, thus are often used in die-casting. Because they are so hard, they also tend to chip much easier than thru-hard pins. It is possible to drill and tap the larger pins because the core is 40-45 RC. Most of the time, anyway! Nitride pins are made of H-13.
  3. Black ejector pins are not so common, and were developed for high temperature applications. They are specially coated for this purpose, and are also self lubricating. Their higher cost makes them somewhat of a specialty pin.

Mold components suppliers

Once you settle on one or more suppliers, work with them to establish good working relationship; you never know when your next crisis will occur.

Ejector Pins For Injection Molding
Ejector pins

There are numerous high quality companies offering industrial supplies, and many specialty suppliers. Here is a partial list:

Standard mold component suppliers for ejector pins


Specialty suppliers of mold components

IpscoEzellHommerPrecision Punch
Punches and PinsParker PrecisionDaytonCumsa

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