General information General information Defi nitions and angles, centres and fl ute forms Chamfer forms, selection and application

When cutting internal threads, all the is carried The length of chamfer is determined by taking into account chamfer lead length of driving length shank dia. out by the cutting teeth of the chamfer. Therefore, a decision various conflicting factors. To avoid overloading, premature driving square on the best type of chamfer form has to be carefully made bluntness and oversize threads the number of chamfer cut- tread dia. as both life and quality of thread are thereby greatly ting threads must not be kept too low. A too long chamfer thread length affected. lead, however, increases the torque and thus the danger of flute breakage. The spiral point with form B ensures a chip remo- length Generally speaking, the form and length of chamfer depend val always in the direction of feed. overall length on the type of hole to be tapped. The tapping of through holes does not normally give rise to any difficulties whereas the production of blind holes can create certain problems included angle associated with the need to evacuate swarf in the reverse Taps Technic of thread land αα width of δ = direction to the feed, i.e. up to the flutes of the tap and then δ δ land γ fA = spiral point angle cut off such swarf when the tap is reversed out of the hole. through hole blind hole γ γ α =clearance angle chamfer fA fA dia. γ γ =rake angle width of γ flute web dia. flute chamfer thread pitch

Flute forms straight fluted, form C helix angle without spiral point 15° Chamfer forms to DIN 2197 straight fluted, form B helix angle Form A with spiral point 40° 6…8 threads long, 6 - 8 threads for short through holes

Types of centres (standard, to DIN 2197/DIN 2175) Form B 3.5…5.5 threads medium, 3.5 - 5.5 threads, with spiral point, solid cone 1 4 solid cone for all through holes and deep tapping holes in medium and long-chipping materials on cutting on stepped cone 2 section shank 5 chamfer Form C internal centre internal centre 2…3 threads short, 2 - 3 threads (form A or R to DIN 322 3 6 (form A or R to DIN 322 for blind holes acc. to manufact. specification) acc. to manufact. specification) and generally for aluminium, grey cast iron and brass

Centre on cutting section Form D Thread dia. range with chamfer forms with chamfer form Centre on shank 3.5…5 threads medium, 3.5 - 5 threads mm A, C, D, E B for short through holes ≤ 4.2 ➀ ➀ ➃ ➄ ➅ > 4.2 … 5.6 ➀ ➁ ➀ ➃ ➄ ➅ > 5.6 … 10.0 ➀ ➁ ➂ ➀ ➁ ➂ ➃ ➄ ➅ Form E > 10.0 ➂ ➂ ➅ 1.5…2 threads extremely short, 1.5-2 threads, for blind holes with little run-out depth. Coolant duct geometries Avoid use if possible.

axial coolant axial coolant Form F delivery delivery with radial 1…1.5 threads extremely short, 1-1.5 threads, with axial coolant coolant duct exit in the flutes for blind holes with duct exit at the chamfer little run-out depth. Avoid use if possible.

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