A hob is a screw-shaped cutter with helical flutes; the hob and the blank rotate continuously together while the hob feeds axially. The result is a generated involute tooth in a single setup. A shaper cutter looks like a gear and reciprocates up-and-down through the blank, indexing one tooth at a time. Hobs are faster and more accurate for production; shapers can cut internal gears and gears with shoulders close to the tooth (which a hob cannot reach).

Module (M) is the metric unit of tooth size: M = pitch diameter ÷ number of teeth (millimetres per tooth). A 40-tooth M2 spur gear has a 80 mm pitch diameter. Cutter specs read in this order: module, pressure angle, material, standard, accuracy class, helix hand. Example: M2-PA20°-HSS-Co-DIN3972-AA-RH = 2 mm module, 20° pressure angle, cobalt HSS, German hob standard, accuracy class AA, right-hand helix.

20° is the modern global default (ISO 53, DIN 867) - quiet, strong, low undercut, easy to manufacture. 14.5° survives only on legacy American machinery and old American clock work; modern shops can almost always retrofit to 20°. 25° appears in heavily loaded automotive transmissions where stress capacity matters more than smoothness. If you don't know, default to 20°.

Each cutter in a DIN 880 set covers a tooth-count range. #1 cuts 12-13 teeth, #2 cuts 14-16, #3 cuts 17-20, #4 cuts 21-25, #5 cuts 26-34, #6 cuts 35-54, #7 cuts 55-134, and #8 cuts 135-rack. Pick the cutter whose range includes your tooth count. The chart is usually printed inside the set's case.

Plain HSS (M2 grade) is the budget option for low-volume work in mild steel and aluminium. HSS-Co (M35, 5% cobalt) lasts 2-3× longer in alloy steel and stainless - the production-shop default. PM-HSS and TiN-coated HSS-Co extend life again at higher cutting speeds. Solid-carbide hobs exist for high-speed dry hobbing on production lines but are 5-10× the price; reserve them for shops cutting hundreds of gears per day.

Approximately, yes - if the helix angle is less than about 5° and you swivel the dividing head accordingly. For helix angles above 5°, the milled tooth shape no longer matches a true involute and the gear will run noisy or seize at load. Use a hob (which generates the correct profile at any helix angle) for any helical work above 5°.

DIN 3968 grades the manufacturing accuracy of gear hobs into seven classes - D (roughest), C, B, A, AA, AAA, AAAA (mastergrade). AA is the standard production class for cutting ISO Class 6-7 gears (typical industrial gearboxes). Drop to A for Class 8 commercial work; specify AAA for ground precision gears or master gears.

Yes - hobs are designed for re-sharpening. Grind only the rake face (top sharpening); never touch the relieved tooth flanks or you destroy the profile. A typical HSS hob takes 5-10 re-sharpens before it loses enough OD that the tooth profile shifts out of tolerance and the hob has to be replaced. Cobalt HSS hobs sharpen 2-3× as many times.

A worm hob is essentially a screw cutter - it generates the tooth profile of a worm wheel by mirroring the worm shaft profile. The mating worm and worm wheel are then meshed at 90°. A spline hob produces parallel-sided splines on shafts (DIN 5480 or similar) - the splines are straight along the shaft axis and engage a matching female spline coupling. Different geometry, different application, not interchangeable.

Indexable carbide gear hobs and shaper cutters exist - usually from Sandvik, Iscar, or LMT - and we can source them on lead time. They make sense at high production volumes where the tool-cost-per-gear works out lower than re-sharpening solid-carbide. For most UAE workshops, solid HSS-Co remains the better economic choice.

Wipe the cutter clean of swarf and coolant, apply a thin film of rust-preventative oil, and store in the original case (or a wooden block with the cutter axis horizontal). Avoid stacking heavy cutters on top of each other - the tooth tips can chip if loaded across the flutes. Keep humidity below 60% to prevent flash rust on the rake face.

Yes - we run a profile-grinding service via Tooltech for one-off and small-batch custom cutters: special pressure angles, non-standard modules, worm tooth forms, repair-replacement cutters for legacy gearboxes. Provide a profile drawing, a sample tooth, or a CAD file and we'll quote on lead time (typically 5-10 working days).