Vertical follower grinder: how it works and where it fits

• 1
  What a vertical follower grinder actually does
• 2
  Main structure of a vertical follower grinder
• 3
  Why grinding burns parts, and how to avoid it
• 4
  Choosing a wheel and setting the machine
• 5
  Step by step: a stable grinding setup
• 6
  Vertical follower grinder vs CNC machining: which route fits

A vertical follower grinder holds the work on a table or chuck and brings a rotating grinding wheel down from above. The spindle axis is vertical, so the wheel face contacts the work surface across its full width instead of along one line. That geometry spreads the cut over more abrasive at once.

The word follower refers to the relationship between the wheel and the work. The wheel follows the surface it is generating, guided by the down-feed and by the table motion underneath. On flat work the table traverses in X and Y while the head steps down in Z. On cylindrical work the part rotates and the head advances radially.

The result is a surface produced by many small abrasive grains, not by a single cutting edge. Each grain removes a chip a few micrometres thick. Because the grains are bonded in a wheel that wears slowly, the geometry stays stable over a long run, which is why grinding holds tight flatness and finish better than milling on the same part.

• 1
  Vertical spindleWheel approaches from above; contact is distributed over the wheel face.
• 2
  Down-feed controls depthTypical roughing steps 0.01–0.03 mm, finishing 0.002–0.005 mm.
• 3
  Table or chuck holds workMagnetic chucks suit ferrous plate; fixtures suit non-ferrous and odd shapes.

The base is a heavy casting, usually ribbed, that absorbs vibration from the spindle and the table. Vibration is the main enemy of surface finish. A base that rings or flexes shows up as chatter marks spaced at the wheel rotation frequency, and no amount of feed adjustment removes them.

The column carries the grinding head and the vertical slide. Its stiffness sets how deep a cut the machine can take without deflection. On a small bench unit the usable down-feed per pass is measured in thousandths of a millimetre; on a floor-standing machine with a box column, roughing passes of 0.02–0.03 mm are normal before a spark-out pass.

The table or rotary chuck provides the feed motion. A reciprocating table gives straight-line grinding; a rotary table gives face grinding on rings, discs and bearing seats. The spindle runs on precision bearings and is often the first component to need service. Bearing preload, wheel balance and coolant delivery all decide whether the finish lands at Ra 0.8–1.6 μm or better.

• 1
  Base and columnRibbed castings damp vibration; stiffness sets maximum depth of cut.
• 2
  Spindle and wheel headBearing preload and wheel balance drive finish consistency.
• 3
  Feed axesReciprocating table for flats, rotary chuck for discs and rings.
• 4
  Coolant and filtrationFlood coolant carries heat and swarf away from the contact zone.

Grinding converts most of its energy into heat inside a very small contact zone. If the heat leaves with the chip and the coolant, the part stays cool. If it does not, the surface layer softens, oxidizes or cracks. A blue or straw tint on a ground steel face is a burn, not a polish.

Three variables decide where that heat goes. Wheel speed sets how fast grains slide through the cut. Depth of cut sets how much material each pass removes. Coolant pressure and nozzle aim set how much heat the fluid can carry away. Increase any of the first two without improving the third and the risk of burn rises.

On hardened steel, a burnt layer can be softer than the core, which is worse than no grinding at all. For tool steel and 17-4PH parts, we use shallower finishing passes, a softer grade wheel and a coolant stream aimed directly at the contact arc. A spark-out pass with no extra down-feed lets the wheel spring back and clean the surface.

Dressing matters too. A glazed wheel rubs instead of cutting, and rubbing is heat. Dressing opens the grain and restores the wheel profile. How often you dress depends on the material and the wheel, but a wheel that starts to burn a part usually needs dressing before anything else is changed.

• 1
  Burn signsStraw, blue or dark tint, micro-cracks, a soft layer under the surface.
• 2
  ControlsWheel speed, depth of cut, coolant pressure and nozzle position.
• 3
  DressingRestores wheel sharpness; a glazed wheel rubs and generates heat.

Abrasive type comes first. Aluminum oxide wheels cover most carbon and alloy steels. Silicon carbide suits cast iron, non-ferrous metals and carbide. Cubic boron nitride and diamond wheels cost more but hold form on long runs and hard materials.

Grit size trades finish against removal rate. Coarse grits of 46 to 60 remove stock quickly and leave a rougher surface. Grits of 80 to 120 are a common middle ground. For a finish near Ra 0.2–0.8 μm, finer grits plus a spark-out pass are the usual route.

Grade and bond control how the wheel behaves under load. A softer grade releases dull grains sooner and runs cooler, which suits hard or burn-prone parts. A harder grade holds form longer, which suits soft material and form grinding. Vitrified bond covers most general work; resin bond suits high-speed and cut-off operations.

Then set the machine. Balance the wheel, true it, and check the table for lost motion. Set roughing depth around 0.01–0.03 mm per pass, then reduce to 0.002–0.005 mm for finishing. Keep the coolant flowing before the wheel touches the work, not after. A clean chuck face and a deburred part seat prevent taper that no wheel change will fix.

• 1
  AbrasiveAluminum oxide for steels, silicon carbide for cast iron and carbide.
• 2
  Grit46–60 for stock removal, 80–120 for general work, finer for finish.
• 3
  GradeSofter for hard or burn-prone parts, harder for soft material and form work.
• 4
  Depth0.01–0.03 mm roughing, 0.002–0.005 mm finishing, then spark out.