1、UDC 531.717.8.084: 620.164.1 .O54325 DEUTSCHE NORM August 1984 I 1 Surface plates Natural hard rock surface plates Requirements and testing e - DIN 876 Part 1 Term 1 -1 Length DIN Material number X : width natural (I hard X b), rock in mm :- Prfplatten; Prfplatten aus Naturhartgestein, Anforderungen
2、, Prfung This standard, together with the August 1984 edition of DIN 876 Part 2, supersedes the May 1972 edition of DIN 876 In keeping with current practice in standards published by the International Organization for Standardization (ISO), a comma has been used throughout as the decimal marker. Dim
3、ensions in mm 1 Scope and field of application This standard applies to natural hard rock surface plates which are used as a plane, or datum surface in dimensional metrology, in particular in testing for deviations of form or position. 2 Dimensions, designation I A i + I I I L I -I Figure 1. Dimensi
4、ons 4-1 ,Working surface over - 250 400 630 1 O00 1600 2000 1 O00 3 Requirements 3.1 General The requirements relating to the flatness of the working surface shall only apply to surface plates resting on three supporting feet, to be specified and identified by the manufacturer. For reasons of safety
5、 and in order to limit the amount of deflection under load, provision may be made for additional safety feet. No supporting feet need be provided for surface plates of length 1 not exceeding 400 mm; such surface plates may be laid flat on the entire under- surface. The surface plates shall be secure
6、d against displacement and tipping and shall not be exposed to a vertical gradient of temperature, such that heating or cooling affects one surface of the plate only. The temperature difference within the surface plate shall not exceed 2 K. After being cleaned with a damp cloth, the surface plate sh
7、all be left to dry for 2 h. 1 The width O shall be agreed and specified in the standard designation. Continued on pages 2 to 4 Beuth Verlag GmbH. Berlin 30, has exclusive sale rights lor German Standards (DIN-Normen) DIN 876 Part 1 Engl. Price group 5 07.85 Sals No. O105 COPYRIGHT DIN DEUTSCHES Inst
8、itut Fur Normung E.V.- EnglishLicensed by Information Handling ServicesPage 2 DIN 876 Part 1 3.2 Flatness of working surface With the exception of the border zone described in sub- clause 3.7, the working surface shall meet the flatness tolerances tl specified in table 2 below. Table 2. Flatness tol
9、erances t, I I 1 I 4 2+- 100 1 II 6 4+- 60 1 40 III 12 8+- ; In addition, the following specifications shall apply: dmh 1 Straightness tolerance t, in pm, for accuracy grade 630 1 O00 1600 2000 2500 9 12 18 22 27 Accuracy grade I O0 li *Guiding face Figure 3. Clamping slot O 1 Identification of guid
10、ing face (example) Figure 2. Guide slot 2 I For 1, substitute the numerical value of the length, in mm. ,Table 5. Geometr,kai I toler;ces for giide 10;s Perpendicularity Straightness Accuracy grade tolerance tolerance of guide slot Flatness tolerances for some values of I are drawn up in table 3. Ta
11、ble 3. Values for tl Flatness tolerance tl, in Fm, for accuracy grade 1 f 4 11 12 8 7 14 1 2 160 250 400 630 1 O00 1 600 2000 2500 12 13 14 17 20 26 30 35 24 25 28 33 40 52 60 70 3.3 Flatness of a local area of the working surface With the exception of the border zone described in sub- clause 3.7, a
12、ny one local area in the form of a square of 250 mm side length shall meet the flatness tolerances t2 specified in table 4 below. Table 4. Flatness tolerances t2 I I I II I III I 38 58 46 71 1 Size working of local I ire es; toleranc;iinp;, ,5 3.4 Slots By particular agreement, clamping or guide slo
13、ts may be machined in the working surface for the purpose of fastening test devices or objects to be tested. These slots shall be machined in accordance with DIN 650, tolerance class H 12 for clamping slots, and H 8 for guide slots. In the case of guide slots, the guiding face shall be identified as
14、 such, either along the top or on the front face. area of the surface 250 X 250 for accuracy grade The number, type and width o (in accordance with DIN 650), the position of guiding faces (in the case of guide slots) and, if required, a tolerance on parallelism to a side face and the accuracy grade
15、shall all be subject to particular agreement. 3.5 Tapped inserts and fitting inserts By particular agreement, tapped inserts (not exceeding size M 8) and fitting inserts may be let into the working 2) The formulae can also be used for lengths 1 greater than those listed in table 1. The values obtain
16、ed shall be rounded up to the nearest whole pm. COPYRIGHT DIN DEUTSCHES Institut Fur Normung E.V.- EnglishLicensed by Information Handling ServicesDIN 876 Part 1 Page 3 surface and shall be counterbored to a minimum depth of 1 mm. 3.6 Sidefaces Specifications as to the flatness and perpendicularity
17、of side faces shall be subject to particular agreement. They may be provided with tapped inserts for attaching any test or safety equipment required. 3.7 Edges and border zone The toleranced surfaces may be surrounded by a border zone, the width of which shall not exceed 2 % of the width b, or 20 mm
18、, whichever is the smaller. In the case of surface plates with a length 1 not exceeding 250 mm, the edges of the toleranced surfaces shall be rounded off, the radius being not less than 2 mm; for larger sized plates, the radius shall not be less than 4 mm. All other edges and corners shall be chamfe
19、red or rounded off with a minimum of 2.5 mm. 3.8 Material and finish Material: natural hard rock, sound, free of flaws, close- grained and of uniform texture, grade subject to agreement. Finish: ground, and the toleranced surfaces lapped so that a non-wringing surface is achieved. 4 Testing Testing
20、shall be performed without load being applied to the surface plate. The surface plate shall stand level on the supporting feet provided. The border zone described in subclause 3.7 shall not be included in the area tested. 4.1 Flatness overall of working surface The flatness test shall be based on a
21、grid of measuring points such as is shown in figure 4, the points being set at intervals corresponding to the base length ZB of the test device used. Suitable instruments for performing this test are pendulum inclinometers, autocollimators or laser interferometers. Such instruments measure tilts dir
22、ectly, and these may be converted into deviations in height by reference to the base length IB. The recommended base length is ZB = 100 mm; the guideline value for the diam- eter of the pads, which shall be coplanar, is 10 mm. For accuracy grades 1 and 2 surface plates, it is also per- mitted to car
23、ry out the test using an accuracy grade O0 straightedge as specified in DIN 874 Part 1. Ld Figure 4. Grid of measuring points (example) 4.2 Local flatness of working surface For local areas of the working surface, testing is limited to checking the deviation from straightness of profile lines at ran
24、domly selected points on the working surface; the length of the profile line under examination shall not be less than 2 IB and not exceed 354 mm (length of the diagonals of the area of the working surface). The devia- tions from straightness thus determined shall not exceed the flatness tolerances s
25、pecified in table 4. A straightedge conforming to DIN 874 Part 1 may be used as a straight- ness standard. 5 Marking Surface plates conforming to the present standard shall display the following marking on one of the side faces: a) DIN876; b) accuracy grade; c) manufacturers trade mark or name. 6 Ad
26、vice to users The floor area on which the surface plate stands shall be solid, rigid, flat arid level; special foundations may be required to support large surface plates which have a high unloaden mass and which are subject to heavy loading. As a result of their poor thermal conductivity, natural h
27、ard rock surface plates are not suitable for the tempering of test objects. Standards referred to DIN 650 DIN 874 Part 1 Machine tools; T-slots, dimensions Steel straightedges; dimensions Other relevant standards DIN 102 DIN 874 Part 2 DIN 876 Part 2 Reference temperatures for measuring tools and wo
28、rkpieces Knife-edge straightedges; dimensions, technical delivery conditions Surface plates; cast iron surface plates, requirements and testing Previous editions DIN 876 Part 1: June 1950; DIN 876 Part 2: October 1931x; DIN 876: October 1931, May 1972. COPYRIGHT DIN DEUTSCHES Institut Fur Normung E.
29、V.- EnglishLicensed by Information Handling ServicesPage 4 DIN 876 Part 1 m:n:o Amendments The following amendments have been made in comparison with the May 1972 edition of DIN 876: a) The contents have been divided into Part 1, dealing with natural hard rock surface plates, and Part 2, dealing wit
30、h cast b) Translators note. Amendment b) refers to a change in nomenclature that does not affect the English translation and c) No fixed dimensions have been specified for the sizes of the surface plates, only ranges for the length 1. d) Requirements relating to a local area of the working surface h
31、ave been specified. e) Requirements relating to guide slots (if provided) have been specified. f) Requirements relating to the support of the surface plates have been specified. g) Tests have been specified. h) A clause on advice to users has been incorporated. i) Requirements relating to tapped ins
32、erts and fitting inserts (if provided) have been specified. j) Marking has been included in the standard specification. Explanatory notes ISO/TC 3/SC 3 is at present engaged in the preparation of two standards dealing with surface plates. This standard has incorporated some of the interim results of
33、 that work, but the competent subcommittee of the Normenausschuss Lnge und Gestalt (Length and Shapes Standards Committee) has decided not to adopt the proposed international standards in their entirety, not least because closer tolerances are considered desirable in Germany. Re clause 2 As the dime
34、nsional specifications included in previous editions have hardly ever been adopted in practice, the present standard only specifies size ranges for the length I; it is thus necessary when designating or ordering surface plates to specify the actual length and width. The minimum dimensions given for
35、the depth e apply only to new surface plates. The depth of used surface plates that have been resurfaced may as a result fall short of the given dimensions. Re clause 3 It was not considered expedient to specify limiting values for deflection under specific loads; first, because the conditions perta
36、ining to the bearing area are so diverse and, secondly, because testing would have to be performed with special apparatus not normally included in workshop equipment. The depth e is an important factor in respect of deflection and is much easier to test. The values given in table 1 represent approxi
37、mations of depths which may be expected to ensure that deflection does not exceed an acceptable value. It shall, however, be noted that the two most frequently used sorts of natural hard rock, granite and diabase, differ significantly in their respective modulus of elasticity, E? = 39 200 to 64 700
38、N/mm2, Euarp = 94200 to 96 700 N/mmz. In consequence, given identical dimensions, modes of installation and loading, a granite surface plate will exhibit approximately twice as great a deflection as a corresponding surface plate made of diabase. Re subclause 3.3 In order to ensure adequate accuracy
39、in small areas even in the case of large surface plates, a flatness tolerance t2 has been specified for any 250 mm square local area of the working surface. Re subclause 4.1 Grids of measuring points which are required for testing the flatness of working surfaces and which can be framed within the s
40、ide lines and diagonals, are drawn up with the aid of combinations of Pythagorean (triangular) numbers. Some iron surface plates. has thus been omitted. a examples of such ratios are given below: Figure 5. n Re clause 5 m 20:21 :29 3: 4: 5 8:15:17 5:12:13 12 : 35:37 7 : 24: 25 9 : 40 : 41 43,603O 36
41、,870“ 28,072O 22,620O 18,925 16,260“ 12,660“ As international standards also employ arabic numerals to denote accuracy grades, it has been decided to include the DIN number, DIN 876, in the marking of surface plates which conform to the present standard so that doubts may not arise as to which stand
42、ard a surface plate conforms, once the international standards pertaining to surface plates have been published. This suggestion in respect of marking has been adopted for the proposed international standards on surface plates. international Patent Classification E 04 C 2-04 B 25 H 7-02 COPYRIGHT DIN DEUTSCHES Institut Fur Normung E.V.- EnglishLicensed by Information Handling Services
