ASTM_D_3297_-_93_scan.pdf

ASTM D3297 93-0759530 05387313 I,315 m Designation:D 3297-93 AMERICAN SOCIETY FOR ESTING AND MATERIALS 1916 Race St.Philridelphia,Pa 19103 Reprinted from the Annual Book of ASTM Standards.Copyri9ht ASTM If not listed in the current combined index,will appear in the neti&ion.Standard Practice for Molding and Machining Tolerances for PTFE Resin Parts This standard is issued under the fixed designation D 3297;the number immediately following the designation indicates the year of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicatea the year of last reapproval.A superscript epsilon(0 indicates an editorial change since the last revision or reapproval.1.Scope 1.1 This practice defines tolerances applicable to parts molded and free sintered from PTFE resins and to machined parts produced from basic shapes of compression-molded or ram-extruded resins.1.2 The values stated in SI units are to be regarded as the standard.The values given in parentheses are for informa-tion only.1.3 This standard does not purport to address all of the safety standards,if any,associated with its use.It is the responsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Document 2.1 ASTM Standard:D 883 Terminology Relating to Plastics 3.Terminology 3.1 Dejnitions-Definitions of terms applying to this practice appear in Terminology D 883.4.Summary of Practice 4.1 This practice provides minimum practical dimen-sional tolerances for PTFE parts that are molded and free-sintered or machined from stock shapes.Dimensional values are most reproducible when the parts are measured at a stabilized temperature between 22 and 25C(72 and 77F)using agreed upon measuring equipment and procedures.5.Significance and Use 5.1 The tolerances are applicable to conventional mea-suring equipment under controlled environmental condi-tions.Because parts of PTFE resin deform easily,care must be taken during the measuring process.In certain instances,considering cross-section to diameter,the part must be supported without distortion by a suitable future while being measured.Measuring procedures,gages,and fixtures should be agreed upon between the purchaser and the seller.6.Interferences 6.1 Stabilized temperatures of molded or machined parts at time of measurement shall be between 22 and 25C(72 and 77F).Difficulty is experienced between 18 and 2 1C(64 I This practice is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.IS on Thermoplastic Materials(Section D20.15.12).Current edition approved Feb.IS,1993.Published April 1993.Originally published as D 3297-74.L.ast pre.vious edition D 3297-88.2 Annual Book of ASTM Standards,Vol 08.0 I.and 7oF)due to a critical transition zone characteristic of PTFE resins.Figure 1 illustrates this effect.7.Conditioning 7.1 Condition the parts at the established inspection temperature for a minimum of 24 h.A shorter period of conditioning may result in erroneous measurements.7.2 The maintenance of constant relative humidity is not required unless,in filled materials,the filler may be affected by moisture absorption.In this case,the standard laboratory atmosphere of 50 f 5%relative humidity shall apply.8.Procedure 8.1 Molded part configurations and tolerances shall be as shown in Table 1.8.2 Machined part tolerances for customarily used ma-chining methods shall be as shown in Table 2.9.Keywords 9.1 machined parts;molded parts;plastics;PTFE,toler-0 I F-328-150 32 x0 4&s 800 C-200-100 0 100 200 300 FIG.1 Thermal Expansion of PTFE Resin 1 NOTICE:This standard has either been superseded and replaced by a new version or discontinued.Contact ASTM International(www.astm.org)for the latest information.ASTM D3297 93-0759530 0538734 05L m e$)D 3297 TABLE 1 Tolerances for Molded Parts of PTFE Resins Molded Part Rings:Diameter W&l Haight(maximum)Concentricity(OD to ID)Parallakm wail-greater than 2.54 mm(0.100 in.)solll Round:Diameter Height Parallelism solld other man round:Lengths Height(mold diiectbn)Parallelism General:Finish steps:Draft angle Radius or Met,or both TOlWanceS 0.010 mm/mm 0.010 In.jln.0.10 mm 0.004 In.0.100 mm/mm(min 0.254 mm)0.100 ln./h.(min 0.010 in.)0.008 0.008 0.010 mm/mm diameter 0.010 in./in.diameter 0.010 mm/mm 0.010 irk/in.0.100 mm/mm(min 0.254 mm)0.100 in./ii.(min 0.010 in.)0.20 mm/mm of diameter 0.008 in./in.of diameter 0.01 mm/mm 0.010 in./in.0.100 mm/mm(min 0.254 mm)0.100 irk/in.(min 0.010 in.)0.20 mm/mm of bnengm 0.008 ln./ln.of h-gm 0.25 mm min radius 0.010 in.min radius 3.25 km min 128pln.mbl 40 max 4O max 0.25 mm rnin radius 0.010 ill.min radius TABLE 2 Tolerances for Machined Parts of PTFE Resin8 Machining operation Tderanoe Turning/king:All dimensions(OD,ID,and lengths)up to 25.4 mm(1 in.)For eacb additional inch of dimension(OD,ID,and length)add an additional tolerance of ID tolara