An internal grinder is used on the insides of a work piece. In many cases, these grinders are used to smooth small holes or cavities within the item, but they have a wide range of internal operations. Internal grinders are high-precision grinders, often having tolerances many times over that of standard industrial grinders. The high-precision is necessary, as the locations worked upon by an internal grinder are often much smaller and harder to reach than with other equipment. For that same reason, an internal grinder will typically have a more streamlined head to allow it access to smaller places.
The primary function of an internal grinder is smoothing out the inside of holes on a work piece. When an item has a hole or cavity that another item must slide through or sit within, burrs and irregularities can cause the two items to sit improperly. This misalignment may have a negative effect on the piece as a whole. Internal grinders are used to prevent these situations from occurring.
The work head on an internal grinder is usually a small wheel or cylinder. This head spins at a very high rate, sometimes in excess of 50,000 revolutions per minute (RPM), but takes off a very fine amount of material per revolution. This high-speed, low-impact process allows the grinder to work in very small areas with extremely high tolerances. When the process is complete, little finishing work is necessary, as these grinders will usually leave behind a smooth surface.
In addition to the standard heads, internal grinders use other work heads for specific tasks. A common example of this is a cone-shaped head that will drill into the work piece as it grinds, enlarging holes or creating openings. Other head styles, such as balls or barrels, have different applications from the standard grinder head.
Some internal grinders use a design similar to standard grinders. These machines usually perform only basic tasks on easily-accessible areas of a work piece. Other internal grinders have different configurations that allow them to access areas within the piece that are not readily available. These types of grinders will usually have long and thin work heads, occasionally with pivots or hinges included. This allows them to snake within the work piece to access difficult areas.
When the grinder is in operation, the work piece is often rotated counter to the rotation of the work head. This allows the material being removed from the piece to naturally fall from the item. In addition, it keeps the grinding head from creating an area where it no longer has purchase on the piece’s surface.
