1517 0.15 IT 0.35 IT d1 1. Basic principles for determining manufacturing tolerance The manufacturing tolerances specified in this standard are assigned to specific tolerance fields of the holes to be reamed. These tolerances ensure in general that the reamed hole will be within the relevant tolerance field while also guaranteeing economical use of the reamer. It must be considered, however, that the size of the reamed hole could still be outside the manufacturing tolerance of the reamer because of other factors, for example the angles on the cutting edges, the cut of the reamer, the way the workpiece is clamped, the tool receiving socket, condition of the tool machine, lubrication, or the material of the workpiece being reamed. Because of this, special cases may arise where other manufacturing tolerances are more favorable. In consideration of economical production and storage as well as replaceability of reamers made by different manufacturers, however, other manufacturing tolerances should only be used in special cases with real justification. 2. Determining the largest and smallest permissible dimensions of reamers The largest permissible diameter d1 max. of the reamer is 15% of the corresponding bore hole tolerance (0.15 lT), taking into account the largest permissible dimension of the bore hole (see picture). The value of 0.15 lT is rounded up to the next greater whole-number or half µm value. This results in a smooth series of µm values for d1. The smallest permissible diameter d1 min. of the reamer is 35% of the relevant bore hole tolerance (0.35 lT) below the largest permissible reamer diameter d1 max. 3. Simplified determination of the largest and smallest permissible dimensions of reamers To simplify calculations, the upper and lower deviations from the nominal diameter d1 of the reamer for the most commonly used tolerance fields is shown in the tables on the following pages. Using these dimensional deviations, you can calculate the largest and smallest permissible dimensions of reamers quickly and easily. 4. Designation (excerpt) If reamers are ordered in special cases with largest and smallest dimensions that deviate from this standard, the upper and lower deviations of the reamer must be indicated in the designation in µm instead of the ISO abbreviation for the bore hole tolerance field. For example, for a reamer with a nominal diameter of 20 mm, upper deviation = + 15 µm: Reamer 20p 25 p 15 p DIN... A p is used in the designation instead of the plus sign and an m instead of the minus sign. This is because the symbols '+' and '-' cannot be written on all machines, especially the data for processing machines. Insertion of Coolant A cooling lubricant should always be used when cutting. This fulfils a cooling and lubricating function at the same time, with lubrication being the most important function when cutting at low cutting speeds. The demands made on cooling lubricants: • Reduction in friction between metal chips and cutting tool • Washing away chippings and filings • Dissipation of heat Water miscible cooling lubricants are used primarily for cutting although cutting oils can also be used in exceptional cases. Reamers – manufacturing tolerances Excerpt from DIN 1420 tolerance field of bore hole tolerance field of reamer zero line * Relative to the nominal diameter d1 of the reamer nominal diameter largest dimension of the bore hole smallest dimension of the bore hole d1 max. of reamer d1 min. of reamer lower deviation* upper deviation* 11 Index 10 9 OIL 8 7 6 5 4 3 2 1
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