Disclosure to Promote the Right To Information Whereas the Parliament of India has set out to provide a practical regime of right to information for citizens to secure access to information under the control of public authorities, in order to promote transparency and accountability in the working of every public authority, and whereas the attached publication of the Bureau of Indian Standards is of particular interest to the public, particularly disadvantaged communities and those engaged in the pursuit of education and knowledge, the attached public safety standard is made available to promote the timely dissemination of this information in an accurate manner to the public. इंटरनेट मानक “!ान $ एक न’ भारत का +नम-ण” Satyanarayan Gangaram Pitroda “Invent a New India Using Knowledge” “प0रा1 को छोड न’ 5 तरफ” Jawaharlal Nehru “Step Out From the Old to the New” “जान1 का अ+धकार, जी1 का अ+धकार” Mazdoor Kisan Shakti Sangathan “The Right to Information, The Right to Live” “!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता ह ै” Bhartṛhari—Nītiśatakam “Knowledge is such a treasure which cannot be stolen” IS 2285 (2003): Engineering Metrology - Measuring Equipment - Cast Iron Surface Plates [PGD 25: Engineering Metrology]
Transcript
Disclosure to Promote the Right To Information
Whereas the Parliament of India has set out to provide a practical regime of right to information for citizens to secure access to information under the control of public authorities, in order to promote transparency and accountability in the working of every public authority, and whereas the attached publication of the Bureau of Indian Standards is of particular interest to the public, particularly disadvantaged communities and those engaged in the pursuit of education and knowledge, the attached public safety standard is made available to promote the timely dissemination of this information in an accurate manner to the public.
इंटरनेट मानक
“!ान $ एक न' भारत का +नम-ण”Satyanarayan Gangaram Pitroda
“Invent a New India Using Knowledge”
“प0रा1 को छोड न' 5 तरफ”Jawaharlal Nehru
“Step Out From the Old to the New”
“जान1 का अ+धकार, जी1 का अ+धकार”Mazdoor Kisan Shakti Sangathan
“The Right to Information, The Right to Live”
“!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता है”Bhartṛhari—Nītiśatakam
“Knowledge is such a treasure which cannot be stolen”
“Invent a New India Using Knowledge”
है”ह”ह
IS 2285 (2003): Engineering Metrology - Measuring Equipment- Cast Iron Surface Plates [PGD 25: Engineering Metrology]
IS 2285:2003ISO 8512-1:1990
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Indian Standard
ENGINEERING METROLOGY — MEASURINGEQUIPMENT — CAST IRON SURFACE
PLATES — SPECIFICATION
( Third Revision)
Ics 17.040.30
@ BIS 2003
BUREAU OF INDIAN STANDARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG
NEW DELHI 110002
August 2003 Price Group 6
Engineering Metrology Sectional Committee, BP 25
NATiONAL FOREWORD
This Indian Standard ( Third Revision ) which is identical with ISO 8512-1 :1990 ‘Surface plates —Part 1: Cast iron’ issued by the International Organization for Standardization ( ISO ) was adopted bythe Bureau of Indian Standards on the recommendations of the Engineering Metrology Sectional Committeeand approval of the Basic and Production Engineering Division Council.
This standard was originally published in 1963 and revised in 1974 and 1991. The revision of thisstandard has again been taken up to harmonize the standard with ISO.
For many practical purposes, surface plates serve the user as a plane or datum surface. Surfaceplates are usually of cast iron or granite; other materials may be used provided they comply withthe requirements for quality and accuracy specified in this standard. Granite surface plates arecovered in IS 7327:2003 ‘Engineering metrology — Measuring equipment — Granite surface plates —Specification ( second revision)’ and harmonized with the International Standard ISO 8512-2:1990‘Surface plates — Part 2: Granite’.
The choice between cast iron and granite surface plates depends on the conditions of use;some general information about care and use, testing and moderation in loading of plates is given inAnnex A, B and C respectively. IS 12937:1990 ‘Engineering metrology — Methods of testing straightness,flatness and perpendicularity’ may be referred for accuracy testing of surface plate.
The text of ISO Standard has been approved as suitable for publication as an Indian Standard withoutdeviations. Certain conventions are, however, not identical to those used in Indian Standards. Attentionis particularly drawn to the following:
a) Wherever the words ‘International Standard’ appear, referring to this standard, they should beread as ‘Indian Standard’; and
b) Comma ( , ) has been used as a decimal marker in the International Standard while in IndianStandards, the current practice is to use a point ( . ) as the decimal marker.
The concerned Technical Committee has reviewed the provision of ISO 185:1988 ‘Gray cast iron —Classification’ referred in this adopted standard and has decided that they are acceptable for use inconjunction with this standard.
BIS CERTIFICATION MARKING
Details available with the Bureau of Indian Standards.
For the purpose of deciding whether a particular requirement of this standard is complied with, the finalvalue, observed or calculated, expressing the result of a test or analysis, shall be rounded off inaccordance with IS 2 : 1960 ‘Rules for rounding off numerical values ( revised )’. The number ofsignificant places retained in the rounded off value should be the same as that of the specified value inthis standard.
IS 2285:2003ISO 8512-1 :1990
1 Scope
Indian Standard
ENGINEERING METROLOGY — MEASURINGEQUIPMENT — CAST IRON SURFACE
PLATES — SPECIFICATION
( Third Revision)
This part of ISO 8512 specifies requirements forrectangular or square cast iron surface plates rang-ing from 160 mm x 100 mm to 2500 mm x 1600 mm,as preferred sizes, in four grades of accuracy O, 1,2 and 3.
This part of ISO 8512 applies to new cast iron sur-face plates, cast iron surface plates in use, andthose reconditioned according to their grade.
2 Normative reference
The following standard contains provisions which,through reference in this text, constitute provisionsof this part of ISO 8512. At the time of publication,the edition indicated was valid. All standards aresubject to revision, and parties to agreements basedon this parl of ISO 8512 are encouraged to investi-gate the possibility of applying the most recent edi-tion of the standard indicated below. Members ofIEC and ISO maintain registers of currently validInternational Standards.
ISO 185:1988, Grey cast iron — Classification.
3 Definition
For the purposes of this part of ISO 8512, the follow-ing definition applies.
deviation from flatness of the working surface: Theminimum distance separating two parallel’ planes
between which the working surface can just be con-tained.
4 Nomenclature
For the purposes of this part of ISO 8512, the no-menclature shown in figure 1 applies.
5 Material
Good quality, close-grained, plain cast iron or alloycast iron at least equal to grade 250 of ISO 185 shallbe used; the material shall be sound and free fromblow holes and porous patches. Minor defects inworking surfaces of grades 2 and 3 only may be re-paired by plugging with material of compositionsimilar to that of the plate.
6 Stress relief
After being cast and rough machined, all plates ofgrades O and 1 and of size up to and including400 mm x 250 mm shall be given a suitable treat-ment to relieve internal stresses before being tin-ished. H is strongly recommended that larger platesof all grades be stress-relieved by similar means;however, where facilities for this purpose are notavailable, such plates may be stabilized by naturalageing by agreement with the purchaser.
The manufacturer shall, on request, supply the pur-chaser with a statement of the stress-relievingprocess which the plate has received.
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-
IS 2285:2003ISO 8512-1 :1990
TOP (working surface)Thickness of top, d —
Side or end facesEdge
7b 1
Framing 1=
and ribbing -—1 r—-./’
II \/ \ *
I
Total depth, h J
Corner J
Figure 1 –
7 Preferred sizes
The preferred sizes for cast iron plates are given intable 1. If plates of other sizes are required, the re-quirements of this part of ISO 8512 shall neverthe-less apply.
The lengths of faces of plates shall be within + 5 !40
of the nominal size.
NOTES
1 There may be a transition period, however, until ex-isting stocks of castings are exhausted and before pat-terns for the sizes specified in this part of ISO 8512replace those currently in use. During this period nationalstandards may be unable to make the ~ 5 0/0 tolerancemandatory.
2 It will be seen that the nominal lengths of faces, withone exception, are taken from the R5 series of preferrednumbers; one plate, size 2000 mm x 1000 mm, is in-cluded because it is an established and widely used size,although 2000 is not an R5 preferred number.
Nomenclature
8 Rigidity
Cast iron surface plates shall be made with ade-quate ribbing and the total depth [i.e. the combinedthickness of the top (working surface) and the depthof the framing] shall be such that when a concen-trated load is applied about the centre of the plate,the loaded area shall not deflect below the remain-ing area of the plate by more than 1 pm/200 N. Thelimiting value for deflection applies to surface platesof size 400 mm x 250 mm and larger.
NOTE 3 A test method is given in annex B.
9 Finish of the working surface
The top (working surface) of grades O and 1 platesshall be finished by scraping or other process whichresults in a surface similar to that obtained byscraping. Grades 2 and 3 plates may be finished bythe same processes or by machining.
The bearing area shall be not less than 20 ?4. forgrade O, 15 ?’. for grade 1 and 107. for grades 2and 3. High spots shall be uniformly distributed andthe percentage of bearing area should not be sohigh as to cause wringing.
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IS 2285:2003ISO 8512-1 :1990
NOTE 4 A method of assessing the bearing area isgiven in annex El.
It is not mandatory for plates smaller than size400 mm x 250 mm to extend beyond the framing, butif they do, the top shall extend at least 20 mm andshall be reasonably flat on the underside.
10 General features
10.3 Edges
10.1 Supporting feet of surface plates
All surface plates shall be supported on three feet.Plates larger than size 1000 mm x 630 mm shallhave safety feet. Feet shall be positioned within theboundary of the working surface to minimize de-flection.
NOTE 5 The setting of adjustable feet may affect thedeviation from flatness of the working surface; specificinstructions for adjusting the feet are given in footnote 3to table 1.
The feet shall be smoothly machined, but machiningof the supporting feet into a plane parallel to theworking surface is optional.
10.2 Projection of top
The top of each plate of size 400 mm x 250 mm andlarger shall extend at least 25 mm beyond the fram-ing on all sides; the underside of this projectingsurface shall be reasonably flat for accommodatingclamps
The side and end faces of the plate shall be ma-chined; if the purchaser requires the side and endfaces to be finished straight, mutually parallel andsquare, the tolerances shall be specified in the pur-chasing order.
All edges and corners shall be rounded with a ra-dius of at least 2 mm. Alternatively, the edges andcorners may be chamfered at an angle of approxi-mately 45° using the value given above.
10.4 Handling
The plates shall be provided with means for con-venient handling.
10,5 Clamping methods (i.e. tapped holes orslots)
The use of tapped holes in the plate for clampingpurposes can cause distortion of the working sur-face if high clamping pressures are applied. The
Table 1 – Tolerances on deviation from flatness overallDimensions in millimetres: tolerances in micrometres
Size of plateDiagonal length
Border zoneTolerance on deviation from ffatness overalll) 2) for p ates of grade
(approx.) o 1 2 3
Rectangular160 X 100 188 2 3 6 12 25250 X 160 296 3 3,5 7 14 27400 X 250 477 5 4 8 16 32630 X 400 745 8 5 10 20 391000 X 630 1180 13 6 12 24
1600 X 1 0003)49
1880 20 8 16 332000 x 1 0003)
662236 20 9,5 19 38
2500 X 160031
752960 20 11,5 23 46 92
Square250 X 250 354 5 3,5 7 15 30400 x 400 566 8 4,5 9 17 34630 X 630 891 13 5 10 21 42
1000 x 1 0003) 1414 20 7 14 28 56
1) The bases of the tolerances specified are given in annex D.
2) Tolerances on deviation from flatness overall are expressed to the nearest
0,5 ~m for plates of grade O,
1 }Im for plates of grades 1, 2 and 3.
3) These plates are supplied with more than three feet. Typically, after the plate has been carefully Ievelled by the three primaryIevelling screws, then the remaining supports may be adjusted either so that they are just In contact without disturbing the setting ofthe level or to give a minimum deviation from flatness. The tolerance applies after the supports have been adjusted and set in themanner agreed between the purchaser and manufacturer. These plates should be checked regularly to ensure that the setting has notbeen disturbed.
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IS 2285:2003ISO 8512-1 :1990
onus is on the purchaser whether or not tappedholes or slots in plates are to be provided.
11 Accuracy — Flatness tolerances
11.1 General
Two flatness tolerances are applied, one for theworking surface overall and one for any local areaof 250 mm x 250 mm of the working surface.
A border zone, the width of which shall not exceed2 % of the shorter side with a maximum of 20 mm,may be excluded from these requirements for accu-racy provided that no point on the border zone pro-jects higher than the remainder of the workingsurface of the plate.
11.2 Flatness of the working surface overall
The flatness deviation of the working surface overallshall not exceed the appropriate tolerance for sizeand grade of accuracy specified in table 1.
NOTE 6 Test methods are given in annex B.
In the case of sizes which differ from those in thepreferred range, the tolerance on deviation fromflatness overall should be calculated in accordancewith annex D.
11.3 Flatness of any local area of the workingsurface
The flatness deviation of any local area of250 mm x 250 mm of the working surface shall notexceed
a)
b)
c)
d)
3,5 pm for plates of grade O;
7 pm for plates of grade 1;
15 pm for plates of grade 2;
30 pm for plates of grade 3.
NOTES
7 The tolerances specified above are the same as thoseapplied to the flatness overall of a 250 mm x 250 mmsurface plate (see table 1).
8 Plates with a diagonal length smaller than 354 mm donot permit a 250 mm x 250 mm search area and in thesecases the test on flatness overall serves to reveal localdeviations from flatness.
12 Marking
Each plate shall be legibly and permanently markedor shall bear a designation plate attached to oneface; the following information, in characters notless than 3 mm high, shall be included:
a) the manufacturer’s name or trade-mark
b) the number of this part of ISO 8512;
c) the grade of accuracy.
DESIGNATION EXAMPLE
X & Co. ISO 8512-1 Grade O
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IS 2285:2003ISO 8512-1 :1990
Annex A
(informative)
Use and care of cast iron surface plates
A.1 A surface plate should be located in a circu-lated atmosphere under constant temperature con-trol. Accordingly it should be protected from directsunlight or draughts; in particular, it is important thatthese should not cause a vertical gradient of tem-perature such that the working surface and under-side of the plate are at different temperatures. Forexample, if there is a persistent difference of 1 ‘Cbetween the working surface and underside of aplate 1000 mm long and 250 mm thick, there can bea distortion of about 5 ~m: this is 80 Y. of the totalmanufacturing tolerance in a 1000 mm x 630 mmplate of grade O.
NOTE 9 The cellular form of the framing and ribbing, therelatively thin top of the plate and its thermal conductivityassist in acclimatizing cast iron surface plates readilywhen the ambient temperature returns to uniformity.
A.2 The plate should be supported firmly andIevelled. Stands should be located on a stable foun-dation.
A.3 Attention is drawn to the procedure for settingsurface plates (see footnote 3 to table 1).
A.4 Clause 8 and clause B.3 refer to the rigidityof a surface plate; care should be taken not to over-load a plate. Suggestions regarding reasonableloading are given in annex C.
A.5 Point contact to scraped or machined surfaceplates is not permissible because of local irregu-larities of the surface.
Contact should be made through either an interme-diate precision gauge block, preferably not morethan 10 mm high, or a similar precision distancepiece.
A.6 Use should be made of the available area ofthe plate and should not always be concentrated inone area,
A.7 The surface plate is a datum and should beprotected against damage. The top should be fre-quently wiped clean from dust and other particles.When measurements are being made, a wiping clothshould be spread on the plate for small tools andgauge blocks.
A.8 A common sign of damage is burrs on thesurface. The excess metal may be stoned away bylocal treatment confined to the burr; this operationshould be followed by thorough cleaning fromabrasive dust.
Rusting is a sign of neglect and misuse; it can bereduced by frequently wiping the top when in useand on occasions by gently rubbing with anotherplate using a paste of a little “jewellers’ rouge” andparaffin as a lubricant.
A.9 When the plate is not in use the top shouldalways be kept covered. If the plate is not requiredfor some days the surface should be coated with acorrosion-preventive such as vaseline.
A.10 Plates wear as a result of use. The user candetect evidence of wear by rubbing the plate with asuperior grade plate and studying the rubbed ap-pearance end/or by checking straightness alonglines on the plate and/or by using the datum gauge(see the tests described in annex B).
All Users are advised to take advantage of thespecialist services of surface plate manufacturers tohave plates reconditioned.
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IS 2285:2003ISO 8512-1 :1990
Annex B
(informative)
Testing of surface plates
NOTE 10 Various test methods are available and detailscan be found in technical books; selected typical methodsare outlined below.
B.1 Deviations from flatness overall
B.1.l Surface plates with a gachined finish maybe tested by comparison with a superior grade plateof larger area.
A robust comparator stand is moved on a region ofthe working surface of the larger plate selected forminimum deviation from flatness. The measuringhead having light operating force is carried in a rightextension arm from the stand and is in contact witha gauge block or similar distance piece (seeclause A,5) which is moved on the plate under test.This method is suitable for small plates.
B.1.2 Larger surface plates with a machined finishmay be tested by measuring deviation fromstraightness along various lines parallel to thefaces, and along the diagonals, by comparison witha reference straight edge. The results are then inte-grated into deviation from flatness by relating theresults at the centrepoint of the plate where the twodiagonal surveys cross and at other points wherelines of test intersect.
B.1.3 Plates may also be tested by checkingstraightness along various lines on the plate usinga block which, as it is moved along a line step bystep, tilts according to the deviations fromstraightness,
The tilts may be measured by means of a spirit levelor an electronic level where the block is of an ap-propriate size for testing the plate in some detail,but also large enough to carry the instrument. Theplate should itself be solid enough not to be de-flected by the load of the level and block, and thefoundation should be stable enough to remain un-tilted by the movements of obsetver and apparatus.
Alternatively, an optical instrument, namely anautocollimator, is suitable for observing the tilts ofan exploring block on any of the surface platescomplying with this part of ISO 8512. Plates of
grade O require a sensitivity of reading of 1 secondof arc; less sensitive instruments may be used moreconveniently on coarser grades of pIate.
B.2 Deviations from flatness locally
B.2.1 Inspection of a new plate for deviation fromflatness locally is recommended; moreover it is alsoparticularly necessary if wear is suspected and/or ifthe working surface is not a consistent datum.
B.2.2 Although the methods described, inclause B.1 mayuse 50 or more located positions ofmeasurement for the contour map of a plate, therenevertheless remain local positions, and on largeplates, local areas, which may not be covered in theoverall survey. Accordingly, an exploration offlatness of local areas is necessary, and, for thispurpose, the methods described in clause B.1 canbe applied to many more positions of measurement.However, this approach is cumbersome. Alterna-tively, since local deviations from flatness affect thesurface plate as a datum, they may be tra?!ed by adatum gauge. A typical example of a datum gaugeis shown in figure B.1: it is a freely moved, scribingblock base with three fixed contacts representing a
datum; an extension carries a sensitive indicator incontact with a pad in spring contact with the surfaceplate. H is recommended that insulated handles befitted to isolate the warmth of the hand from the de-vice and to facilitate its use.
B.2.3 The following procedure is recommended
a)
b)
First visually inspect the working surface to noteany irregularities of appearance. The results ofmeasurement of deviation of flatness overallshould be studied to identify where abrupt orlarge changes in contour occur. A rapid sweepof the whole plate can be made with the datumgauge to identify the areas of greatest variation.,
Check areas where the datum gauge showsvariations of. reading exceeding the tolerance onlocal deviation using the methods described inclause B.1.
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IS 2285:2003
ISO 8512-1 :1990
B.3 Rigidity test An end-on view of the apparatus, with the centralsupport @ unloaded, is illustrated in figure B.2b);
B.3.1 A surface plate being subiected to a riaiditv the plate is standing on its three feet.
test is illustrated in figure B.~a): the apparatus -use~ The beam comparator is a rigid structure which iscomprises essentially supported on two feet (Q), each of which can be
a)
b)
c)
a beam comparator @ incorporating a sensitivepositioned along the length of the beam. A third foot
indicator @;@ [see figure B.2b)], which is positioned centrallyalong the beam and offset, is provided to keep thebeam stable. A sensitive indicator @, with its con-
a central mass support @ independent of thebeam;
tact tip pressed against the surface plate, is rigidlyclamped to the centre of the beam.
the requisite number of masses @ [only onemass is shown in figure B.2a)].
Central mass support @ Supportingfeet(two) @ Sensitiveindicator
Figure 6.2 – Test apparatus forrigidi~ test
IS 2285:2003
ISO 8512-1 :1990
The central mass support is independent of the 6.3.3 The difference between the indicatorbeam, and it can be moved, within limits, on the readings for the loaded and unloaded states willsurface plate relative to the beam. The offset foot give the deflection of the plate under the load ap-@, in addition to its principal function as a plied.stabilizer, also serves as a useful fine adjustment forsetting the zero of the instrument as the indicator@ is very slightly offset from the centreline of thetwo feet 0. (This offset has to be very small relativeto the offset of foot @, if inaccuracies in measure-ment are to be minim ized.)
The applied load should be reasonably proportionalto the size of the plate and normally should not beso large as to deflect the plate by more than half thepermitted tolerance on deviation from flatness over-all,
The central area over which the load is appliedshould range from a circle about 120 mm in diam-eter for small plates to a circle 300 mm in diameterfor large plates.
B.3.2 Adjust the beam feet lengthwise so as tospan the diagonal of the surface plate under test; setthe indicator to read on the plate when the beam isin position and note its reading. Then load the cen-tral mass support and again note the indicatorreading, after which repeat the initial unloadedreading.
6.4 Assessment of bearing area
A method for determining the proportion of thebearing area of a scraped plate involves “blueing”the surface and rubbing it with another suitableplate so that the small bearing areas are high-lighted. After “blueing” and rubbing, place’,a smallglass plate”), on which an area 50 mm x 50 mm hasbeen ruled into 400 small squares 2,5 mm x2,5 mm”’), on the surface. Then visually inspect eachsmall square in turn and make a note of the esti-mated fraction of its area (in tenths) which is occu-pied by a “high spot” of the surface underneath.
The addition of all these fractions when divided byfour gives the percentage of the bearing area of thesurface over the region tested.
After testing a few plates using this method, the re-sults obtained coupled with the general appearanceof the bearing areas mean that a fairly close esti-mate can be made of the proportion of bearing areaof a plate merely from its general appearance.
‘) These glass plates can be readily produced like lantern-slides by photographing a chart drawn on paper.
“) The exact size of the squares is unimportant provided that all the squares are of the same size.
IS 2285:2003ISO 8512-1 : 1990
Annex C(informative)
Resistance to deflection of cast iron surface plates under load
The limiting value for deflection (i.e. 1 pm/200 N), asgiven in clause 8, applies to all grades of plate fromsize 400 mm x 250 mm and larger.
The framing and ribbing and the thickness of the topof cast iron surface plates should be designed tocomply with the rigidity requirement. However, theuser may well seek information on the reasonableload that a plate can withstand. The values intable C.1 give the approximate mass, in kilograms,of concentrated load that will cause a maximum de-
flection of half the tolerance on deviation fromflatness overall.
NOTE 11 It should be understood that table C.1 is in-tended to control loading and to complement clause A.4.The relatively generous tolerances on deviation fromflatness overall of coarse grade plates might encourageextreme loadings and consequently overload foundations:the maximum values in table C.1 have accordingly beenlimited to 500 kg. The recommendation to distribute loadsover the available surface applies whenever conditionspermit.
Table C.1 – Maximum concentrated loading of cast iron surface plates (see also clause 0.2)
Dimensions In millimetres; masses In kilocrams
Mass in concentrated load that will cause a maximum deflection of half the tolerance on deviation fromSize of plate atness overall, specified in table 1, for plates of grade
o 1 2 3
Rectangular400 X 250 40 80 160 320630 X 400 50 100 200 390
D.1.l The values specified in table 1 are based onthe following formula:
I= C,l+C*
where
t is the tolerance on deviation fromflatness overall, in micrometres;
i is the nominal length of the diagonal ofthe plate rounded up to the next 100 mm;
c1 and C2 are constants for the grade of plateand are given in table D.1.
Table D.1 — Values for c, and c,
Grade of plate I c1 I C2
D.I.2 In the case of plate sizes which differ fromthose in the preferred range (i.e. those not given intable 1), the tolerance on deviation from flatnessoverall should be calculated using tthe formula givenin D.1.l.
D.2 Basis of table C.1
Table C.1 gives the maximum load for a deflectionnot to exceed half the tolerance on deviation fromflatness overall appropriate to the size and grade ofplate.
EXAMPLE
From table 1, the tolerance on deviation fromflatness overall of a 400 mm x 250 mm plate ofgrade O is 4 pm. When half the tolerance (i.e. 2 pm)is to be the maximum permitted deflection, it corre-sponds to a force of not more than 400 N (i.e.2 x 200 N; see clause 8) or approximately 40 kg ofmass acting as a load (see table C. I).
11
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Amendments are issued to standards as the need arises on the basis of comments. Standards are also reviewedperiodically; a standard along with amendments is reaffirmed when such review indicates that no changes areneeded; if the review indicates that changes are needed, it is taken up for revision. Users of Indian Standardsshould ascertain that they are in possession of the latest amendments or edition by referring to the latest issueof ‘BIS Catalogue’ and ‘Standards : Monthly Additions’. \ ..
This Indian Standard has been developed from Doc : No. BP 25 ( 0181 ).
Amendments Issued Since Publication
Amend No. Date of Issue Text Affected
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