How To Grind Ejector Pins On A Manual Surface
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
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
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.
More ideas on die and mould making