/ THREADING • General dimensions 2) Relief angle on the crests of the entry taper teeth. It These are the total length, head length (for guidance), shaft represents the second level of criticality for the tap or grip diameter, dimension of the faces for the drive. These performance. As a guide, its dimension has a proportionality parameters are defined in each one of the aforementioned of approximately 10x with respect to the above. The world standards: DIN-ISO, ANSI, JIS, BSI and they are demands required for its monitoring - at hundredths of a different for each one of them. The multi-metal taps comply mm - is also notably complex from a technical point of view. with the DIN-ISO standard. •Ta The p diameter measurements Notes It should be noted that for complicated technical reasons (force and friction levels), the tap does not machine the diameter of the thread core or root, therefore this diameter is obtained in the previous hole machining phase. Active geometry encompasses the set of forms and geometrical elements directly involved in the working mechanics of the tap. Grooves or flutes: In addition to configuring the chip removal or cutting face and consequently the cutting angle, these are the elements responsible for holding and/or evacuating the cut chip and conducting the cutting or cooling fluid. They are directly related to the type of tapping to be carried out and, from an overall prospective, there are three main types: Cutting or chip removal angle. • Spiral flutes: standard for extraction of the chip when tapping blind holes of depth ≤1xD. If required, this type can tap any type of hole although the levels are reduced. Nevertheless, the design of the multi-material tap responds to particular criteria based on experimental results to ensure its versatility. Inverse conicity: consists of the progressive reduction of the tap pitch and minor diameters. Orientated in the point-shaft direction, its purpose is to reduce/minimise the innate high friction component in the work of the tap, therefore it is a highly critical element. Its magnitude is compulsorily reduced (> 0.5%) and the quality imperatives and demands in its design and execution reach similar levels to those mentioned for the cutting edge. • Straight grooves with spiral form in a specific area of the point or entry of the tap, also known as form B, Gun or spiral point: standard for ejecting the chip forward in the tapping of through holes in general, preferably >1xD. Entry taper: zone or area of the tip with truncated cone profiles. It carries out the work of machining or producing the thread. The function of the subsequent thread profiles is solely limited to a guiding or back-up action. • α = relief angle • β=rakeangle • γ = edge angle, consequence of the other 2 Even though the 3 angles are important, the relief angle is especially so. In actual fact, taps have 2 relief angles: 1) Relief angle on the teeth flanks or thread profiles. This is a key parameter for the performance of taps. Its dimension is necessarily and strategically small - less than 1°, its special impact on the behaviour of the tap, even at sub- degree levels (decimals of a degree) mean its design is especially critical. In the design, the high demand required - at micron level - for precise control in the execution and measurement of this parameter entails a special technical complexity. For practical purposes there are two standard length variants: 2.5 threads or pitches (type C or short), standard for taps for blind holes (spiral and straight taps). 42 / 4.5 threads or pitches (type B or medium) standard for intermediate taps, intermediate through holes (Form B or Gun taps). diameter measurements of the tap are strategically dimensioned - by means of criteria included in the corresponding standards - in order to obtain the tolerances demanded in the thread to be machined. The assurance of adequate monitoring of the aforemen- tioned parameters requires highly qualified means and resources. An indicator of the means is the specific equip- ment with leading German technology recently purchased by Neco-Tivoly, which provides full measurement assu- rances and responds to the continuing challenge for inno- vation/improvement of our tap. • Active geometry There is a 3° relief angle that affects the crests of the thre- ads, but given its low criticality, we will not discuss it. • Straight flutes: standard in manual tap sets. In machine work, there are used for tapping blind or short through holes, ≤ 1xD, generally, as well as long ≤ 3xD in particular cases such as castings. They cannot displace the chip and therefore must accommodate it inside, therefore their chip volume - accommodation capacity/space ratio is of paramount importance. In combination with the relief angle it forms the cutting or shearing edge. Its levels of criticality and demand are slightly less than those of the relief angle. From the conceptual point of view, its design is associated with the characteristics of the metal to be worked. • Cutting edge: is the element that carries out the cutting action and is configured by three standard angles: In addition to the relief angle, the other characteristic parameter is the length, usually expressed in number of tap threads or teeth. The combination between the number of cuts or flutes (Z) and the number of threads (N), determines the thickness of the cut chip (E) according to the formula E = H/(NxZ), where H is the height of the thread profile in mm (as a guide H = 0.5xP).