precision tools

Precision Grinders, Jig Grinding, and Grinding AccessoriesBy Randy Hough

the precision grinders used in a tool and die shop or injection mold making shop are some of the most important machine tools of all. These silent workhorses include the manual surface grinder, CNC surface grinder, and jig grinder.

With the extensive use of wire EDM the need for precision grinding has diminished in volume, but not in importance. There just is not as much work in the grinding department, but the grinding operation is absolutely essential to the overall process of toolmaking.

Some of the typical work done on precision grinders include the basic squaring up of core and cavity blocks, die blocks, finishing core pins and punches, finishing parting lines and shut offs and fitting slide lock angles.

Just imagine not having the capacity to do these few tasks and the entire process comes to a halt. You may be able to hard mill a lot of the details, and the sinker EDM can do a great deal, but surface grinding is still an essential part of toolmaking.

One of the old school precision grinders is the jig grinder. It is a very precise grinder, capable of many different operations, yet it is often overlooked as a viable machine tool. Besides the round holes, such as ejector pin holes or die openings, there are many unusual things this tool can do.

One good use is the adding of radii on components. This is often done by hand, with sometimes questionable results that tend to take a long time to achieve. Think of ejector blades, for example. The top area needs to have a radius in order to fit in the opening it will work in. If you only have a few to do, it is not hard to do them by hand. However, if you have 50 blades and all of them require 4 corners to be fitted, the jig grinder can do this accurately and quickly.

Both the jig grinder and surface grinder need good accessories in order to perform as they should. The sine plates, precision vises, angle plates and wheel dressers need to be of the highest quality. These need to be so trustworthy that they repeat 100% of the time and do not wear out.

A typical grinding area should include a granite surface plate, surface gage and test indicator, drop indicator and stand, height gage for scribing lines, squaring block and indicator, angle plates, magnetic squaring blocks, magnetic and non-magnetic sine plates, and spin fixtures.

You also need gage pins, gage blocks, and much, much more. It is wise to get the best you can afford, so that the toolmaker can work quickly and confidently.