1、Specification for depth micrometersBS 6468:2008BS 6468:2008 BritiSh StandardPublishing and copyright informationthe BSi copyright notice displayed in this document indicates when the document was last issued. BSi 2008iSBn 978 0 580 61996 0iCS 17.040.30the following BSi references relate to the work
2、on this standard: Committee reference tdW/4 draft for comment 08/30177718 dCPublication historyFirst published January 1984 Second edition november 2008Amendments issued since publicationAmd. No. Date Text affected BritiSh Standard BSI 2008 iBS 6468:2008ContentsForeword ii1 Scope 12 normative refere
3、nces 13 terms and definitions 14 design features 25 accuracy 56 Marking 6Annexesannex a (normative) Methods of test for measuring face and datum face 7annex B (informative) notes on use 8Bibliography 9List of figuresFigure 1 Spindle type S 1Figure 2 rod type r 2Figure 3 deviation from squareness of
4、mean rod axis to datum face of type r depth micrometers 4Figure 4 Position of reading end of thimble to barrel 5Figure a.1 Example of error of traverse 7List of tablestable 1 deviation of reading at minimum capacity 5Summary of pagesthis document comprises a front cover, an inside front cover, pages
5、 i to ii, pages 1 to 10, an inside back cover and a back cover.BS 6468:2008ii BSI 2008BritiSh StandardForewordPublishing informationthis British Standard is published by BSi and came into effect on 30 november 2008. it was prepared by technical Committee tdW/4, Technical product realization. a list
6、of organizations represented on this committee can be obtained on request to its secretary.Supersessionthis British Standard supersedes BS 6468:1984, which is withdrawn.Information about this documentthis British Standard has been fully revised to bring it up to date. Presentational conventionsthe p
7、rovisions of this standard are presented in roman (i.e. upright) type. its requirements are expressed in sentences in which the principal auxiliary verb is “shall”.Commentary, explanation and general informative material is presented in smaller italic type, and does not constitute a normative elemen
8、t.Contractual and legal considerationsthis publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations.BritiSh Standard BSI 2008 1BS 6468:20081 S
9、copethis British Standard specifies requirements for spindle type S and rod type r depth micrometers with a micrometer traverse of 25 mm or 1 in, covering measuring capacities from 0 to 300 mm, or 1 in to 12 in.annex a gives methods of test. advice on use is given in annex B.2 Normative referencesth
10、e following referenced document is indispensable for the application of this document. the latest edition of the referenced document (including any amendments) applies.BS 817, Specification for surface plates3 Terms and definitionsFor the purposes of this British Standard, the following terms and de
11、finitions apply.3.1 type S micrometermicrometer having a single spindle and a measuring capacity of 0 mm to 25 mm or 1 inNOTE Figure 1 illustrates a typical Type S (spindle) micrometer.Figure 1 Spindle type S123 4 5891076KeyMeasuring capacity1 Base2 Spindle clamp (optional)3 Fidicual line4 Barrel5 t
12、himble6 ratchet drive (optional)7 datum face8 Spindle9 Measuring face10 BS 6468:20082 BSI 2008BritiSh Standard3.2 type R micrometermicrometer having measuring capacities of 0 mm to 300 mm or 12 in, in increments of 25 mm or 1 in by means of a series of rods, the measuring faces of which are flatNOTE
13、 Figure 2 illustrates a typical Type R (rod) micrometer.Figure 2 Rod type R34687251KeyMeasuring capacity1 range2 Base3 Fidicual line4 thimble5 Barrel6 datum face7 Extension rod8 3.3 measuring capacity (type S)range of depth which the instrument will measure using the traverse of the micrometer screw
14、 3.4 measuring capacity (type R)range of depth which the instrument will measure using the various rods together with the micrometer screw 3.5 deviation of readingdifference between the depth micrometer reading and the length at 20 C between two parallel planes, one of which is contacted by the datu
15、m face and the other by the measuring face of the spindle or rod4 Design features4.1 Basethe base shall be made of steel, with at least 65 mm length of datum face. the shape shall permit measurement of depth at any point BritiSh Standard BSI 2008 3BS 6468:2008in a circle of 25 mm diameter recessed a
16、t the maximum capacity of the depth micrometer. the datum face shall be hardened to not less than 600 hV, and all sharp edges shall be removed to a maximum of 0.5 mm or 0.02 in width of chamfer. the datum face shall have a surface texture less than 0.1 m Ra or 4 in Ra at a sampling length of 0.8 mm
17、and shall be flat or concave by not more than 0.003 mm or 0.000 1 in.4.2 Spindle and rods4.2.1 Material the spindle and rods shall be made of steel of hardness no less than 640 hV and shall be free from internal stresses. 4.2.2 Hardnessthe hardness of the measuring faces shall be no less than 800 hV
18、. 4.2.3 Flatness and surface texturethe measuring faces shall have a surface texture less than 0.1 m Ra or 4 in Ra at a sampling length of 0.8 mm and the flatness shall not exceed 0.001 mm or 0.000 05 in.NOTE Spindle and rods may be tipped or coated on the measuring face with a wear resistant materi
19、al.When tested in accordance with A.1, there shall be no more than four circular interference bands. Where the datum face is lapped, there shall be no more than ten circular interference bands.4.2.4 SquarenessWhen tested in accordance with A.2, the measuring face shall be square to the axis of the s
20、pindle or rod within 0.003 mm or 0.000 1 in over the diameter of the face.4.2.5 Assembly4.2.5.1 For type S, when assembled, the measuring face of the spindle shall be parallel to the datum face at all positions within 0.003 mm or 0.000 1 in over its diameter. the cylindrical portion of the spindle s
21、hall be a free fit in its bearings with a lateral shake not exceeding 0.015 mm or 0.000 6 in measured within 4 mm of the datum face.4.2.5.2 For type r, the axis of rotation of rods in the instrument shall be normal to the datum face within 0.08 mm per 25 mm or 0.003 in per in of projecting rod lengt
22、h. When an assembled rod is rotated the measuring face centre shall not deviate from its mean axial position by more than 0.025 mm for each 25 mm or 0.001 in per in of projecting rod length (see Figure 3).BS 6468:20084 BSI 2008BritiSh StandardFigure 3 Deviation from squareness of mean rod axis to da
23、tum face of type R depth micrometers12KeySquareness of mean rod axis to base1 datum face2 4.3 Micrometer screwthe micrometer screw shall have a lead of 0.5 mm or 0.025 in. throughout the entire micrometer measuring traverse there shall be no less than 8 mm or 516 in engagement of screw with nut, and
24、 the axial play shall not exceed 0.008 mm or 0.000 3 in.4.4 Thimble graduationsthe thimble shall be graduated with 50 divisions for metric reading instruments, each representing 0.01 mm, or 25 divisions for inch reading instruments, each representing 0.001 in.the diameter of the graduated edge of th
25、e thimble shall be no less than 11 mm or 716 in and the angle of the bevel shall be no more than 20. the distance from the barrel to the thimble edge shall not exceed 0.4 mm or 0.015 in (see Figure 4). the graduation lines shall be uniform and clear, and of width not less than 0.10 mm or 0.004 in an
26、d not more than 0.20 mm or 0.008 in.NOTE 1 The surfaces of the thimble and barrel should have a nonreflective finish, and the graduation lines should contrast with the finish for ease of reading.NOTE 2 Vernier scales are not recommended for depth micrometers.4.5 Assembly of micrometer with bodythe s
27、pindle or rod and screw shall be lubricated with a thin, noncorrosive oil and in this condition the motion shall be free and smooth throughout the travel.4.6 Spindle clampWhen a spindle clamp is fitted, it shall effectively lock the spindle without altering the reading by more than 0.003 mm or 0.000
28、 1 in.4.7 AdjustmentsProvision shall be made for resetting the zero reading and for taking up wear between the screw and nut.BritiSh Standard BSI 2008 5BS 6468:2008Figure 4 Position of reading end of thimble to barrel120.4 mm (0.015 in) max20 max.Keythimble1 Barrel2 5 Accuracythe maximum permissible
29、 deviation of reading at the minimum capacity of the instrument shall be as specified in table 1.When tested in accordance with A.3, the maximum error of traverse of the micrometer shall not exceed 0.005 mm or 0.000 2 in.table 1 Deviation of reading at minimum capacityMetric ImperialMeasuring depth
30、capacityTolerance on deviation of reading at minimum capacity, plus or minusMeasuring depth capacity Tolerance on deviation of reading at minimum capacity, plus or minusmm mm in in025 type S 0.003 01 type S 0.000 1025 type r 0.006 01 type r 0.000 22550 0.006 12 0.000 25075 0.006 23 0.000 275100 0.00
31、8 34 0.000 3100125 0.008 45 0.000 3125150 0.010 56 0.000 4150175 0.010 67 0.000 4175200 0.012 78 0.000 5200225 0.012 89 0.000 5225250 0.014 910 0.000 6250275 0.014 1011 0.000 6275300 0.016 1112 0.000 6BS 6468:20086 BSI 2008BritiSh Standard6 MarkingEach depth micrometer shall be legibly and permanent
32、ly marked, in characters not less than 0.6 mm high, with the manufacturers name or trade mark and country of manufacture.NOTE It is recommended that type R rods be marked with their associated measuring capacity.BritiSh Standard BSI 2008 7BS 6468:2008Annex A (normative) Methods of test for measuring
33、 face and datum faceA.1 Flatnesstest the measuring face for flatness by means of an optical flat. Clean the face thoroughly and bring the optical flat gently into contact with it. When the contact is stabilized, either a general colouration or a few circular interference bands will be seen on the su
34、rface. the bands are more crisply defined if a mercury vapour light is used for illumination. if the datum face is lapped, test it in the same way.if the face is ground, test it by comparison with a Grade 0 granite surface plate in accordance with BS 817, using a dial test indicator (see BS 2795).A.
35、2 Squarenesstest the squareness of the measuring face to the spindle or rod axis by observing the variations of its reflections as viewed by an autocollimator when the spindle or rod is rotated in a vee block.A.3 Error of traverse of the micrometerSupport the datum face on two 25 mm gauge blocks on
36、a Grade 0 surface plate. record the depth micrometer readings as the measuring face is used to contact a series of gauge blocks (see BS En iSO 3650) from 0 mm to 25 mm (e.g. 2.5, 5.1, 7.7, 10.3, 12.9, 15.0, 17.6, 20.2, 22.8 and 25 mm) and plot the results in accordance with Figure a.1.Figure a.1 Exa
37、mple of error of traverse-7-6-5-4-3-2-100 2.5 5.1 7.7 10.3 12.9 15.0 17.6 20.2 22.8 25.012345671Appropriate gauge sizes in mmDeviation of readings ( m)Keyrange of deviation of reading1 BS 6468:20088 BSI 2008BritiSh StandardAnnex B (informative) Notes on useB.1 the micrometer screw should be kept lig
38、htly lubricated with a thin oil and it should run without tightening or slackening during its traverse.B.2 When a rod is fitted to a type r instrument, the seating on the rod and its associated seating in the body should be checked for cleanliness on a regular basis.B.3 the measuring and datum faces
39、 should be kept clean.B.4 the zero reading of the depth micrometer may be checked thus:Type R and type S, 0 mm to 25 mma) . hold the datum face of the depth micrometer in contact with a Grade 0 granite surface plate and bring the measuring face gently into contact with the plate. note the reading.Ty
40、pe R, greater than 25 mm (e.g. 25 mm to 50 mm)b) . Use the datum face as a bridge across two 25 mm gauge blocks and note the reading when the measuring face gently contacts the surface plate.NOTE Each rod gives a different minimum capacity to the depth micrometer and therefore has an individual zero
41、 reading.alternatively, the depth micrometer may be checked for deviation of reading at a particular dimension by holding the datum face to two equal gauge blocks of the nominal depth standing on a Grade 0 granite surface plate and noting the reading of the measuring face on the surface plate.B.5 ac
42、curate use of a depth micrometer depends upon firm contact of the datum face and gentle rotation of the thimble until the measuring face makes contact.BritiSh Standard BSI 2008 9BS 6468:2008BibliographyBS 870, Specification for external micrometersBS 959, Specification for internal micrometers (including stick micrometers)BS 1734, Specification for micrometer headsBS 2795, Specification for dial test indicators (lever type) for linear measurementBS En iSO 3650, Geometrical product specifications (GPS) Length standards Gauge blocksBS 6468:2008 BritiSh StandardThis page deliberately left blank
