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How To Grind Ejector Pins On A Manual Surface Grinder

Mold makers know how to grind ejector pins on a manual surface grinder, and here are several techniques that work quite well.

These methods of surface grinding work not only for ejector pins, but core pins and many other injection mold or die components.

Best way to grind ejector pins

Some bigger shops have ejector pin grinding machines, which are able to cut off and grind in two simple operations. Unfortunately, these are not very common. In fact, I have only used such a machine once, and it was quite impressive.

So, the typical precision machine shop, tool and die making or mold making shop is forced to use a different technique. This usually results in using a homemade ejector pin grinding fixture, or some type of set-up involving Vee-blocks.

I have used a commercially made fixture, and it worked quite well, but, for some reason, these don't seem very popular. As a result, I have my own ways of “skinning this cat”. Knowing how to grind ejector pins is different from shop to shop.

If you can hold the pin in a regular Vee-block, my favorite method is to stick the Vee-block onto a Hermann Schmidt magnetic squaring block, use a parallel for a stop on the surface grinder magnet and grind the pin to length.

If the ejector or core pin diameter is very small and won't work in a Vee-block, you can use a commercially available tool called a Wee-block. These come in two small sizes that work for nearly everything you might come across.

How to grind ejector pins

You can also make a little Vee-block to fit inside your regular Vee-block to accomplish the same thing. In this case though, you need to have a very small point on your Vee-block screw to hold the ejector pin.

Another method is to cut the pins off in a surface grinder by using an abrasive grinding wheel. You can put your Vee-block on a magnetic squaring block and set up a stop to enable repeated cuts.

Once the pins are cut off, you change wheels to use a cupped-wheel for finish grinding. The easiest way to do this is to keep the two wheels on different hubs. This way you just need to change the hub and not waste time changing wheels.

Now, you simply grind the pin to length. This method works great for extra long pins that would not normally fit under the surface grinding wheel in a vertical orientation.

You can dress the cupped-wheel easily by hand to save time. Just use a Norbide stick or a Carborundum stick to dress the wheel. This is a good idea, since the wheel will tend to load up during grinding, if you are doing larger pins, such as return pins.

Make sure to grind from the center of the wheel toward the outside, as this will keep your edge much longer and give you a better surface finish and repeatable length dimension.

So, if you cannot afford to buy an ejector pin cut-off and grinding machine, either make a fixture to cut off and grind your pins, or just use some type of Vee-block set up. As you can see, knowing how to grind ejector pins has many different answers.

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