For Honing videos, click here.
Details to look for during new and used machinery inspection:
Clearance, spindle to column
Table working surface
Coolant pump, OD work holder, special fixtures
What Is Honing?
Honing differs from Grinding in that honing stones have a relatively large area of abrasive in contact with the work at relatively slow speeds and low pressure. Surface temperature is low and there is no surface damage. Grinding, on the other hand, has a relatively high pressure and a line contact between abrasive and bore, and runs at high speeds. Extremely high localized surface temperature is developed and the surface structure of the bore may be permanently damaged. Homing produces greater accuracy and a finer surface finish than grinding, and provides a stress-free base metal surface in the bore.
In internal grinding, support for the grinding wheel is outside the bore, in the spindle bearing. With Sunnen Honing, the part being honed is stabilized on the honing unit itself. Thus there is no deflection between the honing unit and the bore, or any change in the bore�s axis: High accuracy is achieved. This is especially important in long bores with small diameters.
Lapping, on the other hand, is a slow tedious process requiring considerable skill. It employs a tool of soft metal which must be frequently �charged� with a lapping compound. Lapping can produce extreme accuracy but the loose abrasive may cause washouts at ports, lands, and at the ends of the bore.
Sunnen Honing combines the speed of grinding with the accuracy of lapping. Stock is removed first from any high spots in the bore while low areas are bridged by the honing stone until all �peaks� are leveled off. Surface finishes are accurately controlled by the size of the grains used in the stone.
Honing stones are self-sharpening because abrasive grains dislodge when they become dull, allowing sharp new grains to contact the work surface. The honing operation produces geometrically perfect bores with a cross-hatched base-metal finish having thousands of microscopic pockets that are ideal for supporting a uniform lubrication film.
The Sunnen honing process combines precision with economy. Its widespread acceptance throughout industry is proof that �Today�s tolerances and finishes call for honing.�
*This is one article in a series of How to Buy Metalworking Equipment. Each article showcases and explains a particular type of metalworking machine. They were originally published in the Metalworking Machinery Mailer published by the Tade Publishing Group.