Honing is the last step in finishing the bore of a tube or cylinder. A tool carrying abrasive stones rotates and strokes back and forth inside the bore at the same time, removing a few thousandths of an inch and leaving a fine cross-hatch pattern. The result is a bore that is round, straight, sized to tolerance and textured to hold a film of oil — which is what a seal, a piston or a plunger needs to run in it for years.
Pipe or tube honing is abrasive finishing of an internal diameter. It corrects what the previous operation left behind — out-of-round, taper, waviness, tool marks — and sets the surface roughness to a specified value. It does not move the bore or change its position; it refines a bore that is already in the right place.
The difference from grinding is in how the abrasive meets the metal. A grinding wheel spins fast against a line of contact. A hone presses several stones gently against the whole wall, at low speed, and averages out the errors. That is why honing reaches tighter roundness and a more even finish in a long bore, with much less heat.
The hone is a body with abrasive stones mounted on shoes that expand outward under controlled pressure. Stones are bonded aluminium oxide or silicon carbide for general work, diamond or CBN for hard steels and long runs. As the tool rotates and reciprocates, each stone traces a helix, and the crossing helixes produce the cross-hatch.
The stones only keep cutting while they are clean. Fine swarf and broken abrasive grains fill the spaces between the grains — the stone loads — and a loaded stone rubs instead of cutting, glazes and heats the bore. Keeping them clean is the job of the fluid.
A honing oil is a low-viscosity neat oil, much thinner than a cutting oil. It flushes swarf and abrasive fines out of the stones so they keep cutting, carries the heat away from a long stroke, and leaves a clean surface behind. A heavier oil clings to the stones and loads them; a water-based coolant can do the job on some machines but gives up lubricity.
We supply EASYCUT NHO051 Honing Oil in 5-gallon pails, 55-gallon drums and 270-gallon totes. Because the oil recirculates, filtration matters as much as the oil itself — fines that get past the filter end up back in the bore. On machines that run hot, mist collectors keep oil mist out of the shop air, and if a machine runs a water-based honing fluid instead, an oil skimmer keeps tramp oil off the sump.
