JIS S8502-1973 (revised from 1969)

This JIS concerning "Disk Records" was further revised in 1976 and replaced by S8601-1981 which was abolished in 1994 at last. JIS made a rule for revision every 3 years from April 1974.

The dimensional standards for Disk Records specified in JIS S8502-1973 (unit: mm if not specified)

My analysis about the angles of raised rim. In case of 175degrees for raised rim, the maximum outer blank width from the edge to the recorded groove might happen to be more than 5mm. It contradicts with the maximum recorded outer diameter 292.6mm (though this is not contradiction since both maximum values are set separately-incompatible). There can be two ways of solution. The blank width can be reduced by setting rim angle as in case of old JIS. Another (more practical and simple) method is to make the recorded groove starting at inner radius (less than 144mm) or discontinue raised rim and make record flat with sufficient lead-in width. The latter is adopted in the recent design of records since groove guard became unnecessary for usual record players: stack of records for auto-changer is outdated.

The thickness of music groove area is not specified for the record with raised rim since the thickness of recorded area is usually increasing towards inner (the thinnest point is located at the foot of raised rim). Often the peripheral edge has burrs.

     In a cold winter day I screwed a record from shelf forcibly. Then it was broken. So I had chance to measure thickness of this low-priced Seraphim (Toshiba-EMI) record: Outer rim thickness 1.7mm/foot of raised rim 1.2mm starting music/middle groove 1.3mm/inner groove 1.4mm/label area thickness 1.7mm.

I notice minor difference between JIS and BS/IEC drawings. The thickness of music groove area looks unchanged (non-tapered) in BS/IEC drawings (or their drawings do not clarify this specific point) while the thickness of the record groove area is reduced towards the rim in many records. I think these records follow the contour as proposed in US patent 2846230 assigned to RCA which tells as follows: label area thickness, for example, be .075". The record groove area has a maximum thickness immediately adjacent the label area. This maximum thickness is slightly less than the thickness of the record at the label area. For example, the thickness of the record groove area at its point of maximum thickness may be .065". This record groove area tapers from the maximum thickness aforesaid to a minimum thickness at the outer periphery of the record groove area. The thickness of the record at the region of minimum thickness may, for example, be about .045". Surrounding the record groove area, there is a marginal area. The marginal area or portion has a maximum thickness greater than the average thickness of the record groove area but less than the thickness of the label area. The thickness of the marginal area may, for example, be of a thickness corresponding to the accepted standard thickness for the rim of phonograph records, whereby the record may be used with automatic record changers of  the type wherein the selection of  the records is affected at the rim of the record. This thickness may, for example, be .065" ...
I think both master lacquer and stamper film are not tapered. Then groove of tapered design is little inclined? The rate of inclination at music groove is less than 0.2 degree from DEGREES(ASIN(0.35/100)) for example. Actual radius variance due to small taper shape is negligible compared with the rate of expansion of nickel stamper during heat press procedure. Stamper film or foil is flexible.

I find following drawing from US patent presenting the idea of raised rim for sound groove protection. This patent referred to "the flexible stamper" in making raised rim.
My note: This invention indicates lead-in groove started in raised rim while usual record with raised rim is designed to make lead-in groove starting from the end of raised rim. In my collection of records I find both types. Raised rim near the edge of record has often deformation so that I encounter problem of tracing on lead-in groove on raised rim. Raised rim has advantage (reinforcing thin disc record and protecting recorded area) and disadvantage (records tend to be warped due to torsion during or after pressing process). 

BS1925-1965 (same as IEC98-1964)

Drawing for 25cm and 30cm records. Middle values of outer diameter: 301.6mm/type III and 250.8mm/type IV each allowance +/-0.8mm. 

IEC98-1987

Drawing for 25cm (type 2533) and 30cm (type 3033) records. Middle values of outer diameters: 301.6mm for Type 3033 and 250.8mm for Type 2533 each with allowance +/-0.8mm.

Thickness was specially defined in IEC 98 (1958)
    E5 Disk thickness:The thickness of 78 rev/min coarse groove and 33 1/3 rev/min fine groove records shall be as follows:
                    The thickness of the thickest part of the record shall lie between the limits of:
                                        0.090 in (2.30 mm)
                                        0.059 in (1.50 mm)
                    For the thickness of 45 rev/min fine groove records see Fig.1, page.26.
IEC 98 (1958) had not indicated figures for LP and SP records.

Thickest part is located at label area so that rubber mat on platter has usually recess for label area.

Hereunder I reproduce my comparative table for 30cm LP adding column for JIS.

Remarks* on above table:

*1.     In the first edition of IEC98 (Section F5 Page 21) the "minimum diameter of recorded surface" is quoted for transcription recordings (for broadcasting use) only. There is no corresponding description about minimum diameter for commercial disk records (Section E).

*2.    I picked up the figures for IEC98-1964 from BS1928 as BS1928-1965 is based on 2nd edition of IEC(1964). Mirror documents with respective notes when BS differs from IEC descriptions.

*3.    JIS prescribed for the quality of records as under and commented on warps: "It is not easy to make rule against warps which have complex forms and nature. Hence we checked representative warps of wavy or shallow dish. On our investigation such warps (height change) within 2mm will not cause any practical problem on playing back such records, while it is not possible to control the way of storage and final distribution to consumers. We observed that the warps less than 1.5mm at production had not increased to warps more than 2mm under normal storage conditions at distributors, so that we specified maximum warp to be 1.5mm."
How to measure warps according to JIS: For dish-like warps, set height gauge on the half radius of label area and push down both ends of label area flat with fingers and measure the difference of height. For wavy warps, set height gauge on the recorded outer groove (3-5mm from the rim of record) and rotate the turntable slowly (=by hand?) more than one turn and measure the difference of height.  I have the impression that factory sealing with shrink film itself as recent commercial practice is the cause of warp after production (due to stress of film shrinkage) . Old records without sealing were found much better than recent issues sealed with shrink films. Or old records too had warps sometimes but such might be destroyed or not resold so that old records on market are found to have less warps. Or recent issues are produced under poor quality control or check system since some pressed records have imperfection  (trimming error, off centre press, miss-press due to mould or uneven mixing of materials etc) still in the process of analog disks production. 

For comparison I introduce some common/accepted values of dynamic range and SN ratio among different analogue disks. Of course the same format/media can have different value according to circumstances. "Acetate/cellulose 78rpm" indicates instantaneous recordings for broadcasting use around 1950. I picked up these data from a dissertation (once downloadable, now missing).

*4.    As per Amendment Slip No. 1 published 26 January 1972 to BS1928-1965 

*5.    Diameter of concentric finishing groove 98.4mm was quoted for 45 rpm record. Corresponding finishing groove radius for 33.3rpm record was under consideration at the time. 106.4+/-0.8mm was quoted in DIN 45537(Monaural Records 33.3rpm) & DIN 45547(Stereo Records 33.3rpm) both Nov. 1962. 

*6.    DIN 45537 in 1962 (Monaural Records 33.3rpm) indicated top width: more than 55micron while bottom radius less than 4micron. By the way it is uncertain whether monophonic groove dimensions in stereo age/cutter were differing from monophonic groove dimensions in original monaural age/cutter or not. It may depend on the density of pitch (for example: original two sides recordings can be compressed to one side by the development of cutting engineering) or the cutting engineer's idea at the time. Since 1970 it was believed that the minimum top width of monophonic groove could be reduced to 30microns as indicated in IEC98-1987 though this standard has not clarified its application to monophonic groove. I think Amendment Slip No. 1 published 26 January 1972 to BS1928-1965 (where the tip radius 0.6-0.7mil can be commonly recommended for both monophonic and stereophonic application) is corresponding to this change of minimum top width for monophonic groove. 

*7.    RIAA in Bulletin E 4 (1963) commented "Note: This figure does not imply that a record having this degree of run-out would be acceptable from a quality standpoint. It does provide, for instance, a limit for the maximum sensitivity or a velocity trip when combined with the pitch of spirals between individual bands".  My note: marker space between bands is 1mm pitch/turn usually. Four types of auto-lift-return mechanism for arms: a. Position Trip at specified radius of groove/ b. Progress Trip (finishing groove) / c. Eccentric Trip for SP lead-out groove/ d. Velocity Trip actuated by velocity of arm swing at lead-out pitch. Run-out 0.050" max. (1.27mm) in this RIAA standard is safeguard against actuating auto-lift-return mechanism for some auto players. For instance, velocity trip for Yamaha YP-D8 is adjusted around 3mm pitch/turn matching with the minimum lead-out pitch in standards.  Anyway RIAA's explanation was not straightforward - it was better to specify max. eccentricity 0.01 inch or around. Maybe RIAA reserved such strict specification considering the status of record industries in those days. 

In 1978 RIAA revised their Bulletin E 4 DISC PHONOGRAPH RECORDS FOR HOME USE incorporating metric as well as English unit of measure, and using decimals rather than fractional dimensions. Their standards for 78-rpm discs and serration standards for 45-rpm discs have been deleted from bulletin. Also "the Standard Recording and Reproducing Characteristic," Bulletin E 1 has been incorporated in 1978 version. Remarking "These are dimensional standards to faciliate equipment desingn and assure interchangeability. They are not intended to indicate or imply quality or performance levels." Additional remark to *7:"The standard for groove-runout or eccentricity has been revised from the old limit of 0.050" to a Total Indicated Run-out (TIR) 0.016"(0.41mm)." It seems that this new RIAA standards follow BS 1928(1965 and 1972 amendment slip) indicating Center of Gravity as 11.1mm(0.437") etc.
Meanwhile NAB[1964] showed idealistic strict specifications: [clause 2.15] eccentricity of hole to groove spiral within 0.005 inches (0.127mm) and [clause 2.20] warp height "not be in excess of 1/16 inches" for one turn and "not exceed 1/32 inches" for any 45 degrees segment. I think the latter demand [warp within 0.8mm (1/32 inches) for any 45 degrees segment] is not always practicable since some records have wavy warps at rims. If such is played with heavy pickup system, stylus jumps. Hence light system (arm+pickup-head) is preferable. Low inertia arm was developed mainly from 1970s.

B.S.1928-1965 was prepared and approved by the Acoustics Standards Committee consisting of BBC, British Electrical and Allied Manufacturers' Association, British Radio Equipment Manufacturers' Association, Radio and Electronic Component Manufacturers Federation etc. 

JIS (Japanese Industrial Standard) S8502-1973 was prepared by RIAJ (Recording Industry's Association of Japan) and approved by MITI (=current METI). 

Many German standards were prepared by the German Electro-technical Committee (Deutsche Elektrotechnische Kommission=DKE) in DIN (Deutsche Institut fuer Normung) and VDE (Verband Deutscher Elektrotechniker). "DKE" is combination committee between DIN and VDE since 13th October 1970. VDE has been leading group for making practical electric standards since its start on Jan. 1883. The history of DIN is little complicated: In 1917 NADI (Normenausschuss der deutschen Industrie=German Industrial Standards Committee) was founded, in 1926 DNA (Deutschen Normenausschuss=German Standards Committee) was founded and finally in 1975 current name DIN was adopted by changing its name from DNA. "DIN" does not stand for Deutsche Industrie Norm (German Industrial Standard) directly, but a standard approved by Deutsche Institut fuer Normung (German Institute for Standardization). But since any standard is implicitly connected with industry, DIN can be interpreted as Deutsche Industrie Norm (German Industrial Standard).

GROOVES：　In fact record has One Spiral Groove each on the face. The grooves in the following definition are counted on cross section.

1. Beginning of groove （plain groove without signal)

2. Lead-in grooves (at least one turn): pitch 1.2mm+/-0.4mm per turn (we find some irregular records having wide lead-in pitch such as 2mm starting on the slope of raised rim). Usually 2-3 turns of 1.2mm pitch plus one reduced pitch before music groove. The stylus happens to fall in this groove. But actually stylus is landing more often between the grooves　- then tip is dragged eventually into groove during one turn of record.  The lead-in pitches of some records start in the slope of raised rim so that stylus tends to skip the grooves.  Hence BS1928-1965 commented specially as follows: NOTE 1. For 33 1/3 rev/min records having a raised rim, it is desirable that the maximum lead-in pitch be 3/84 in (1.2mm) and the top width of lead-in groove be 0.004 in to 0.006 in (0.10mm to 0.15mm).

3. Beginning of music groove which has often additional turns of mute plain groove with normal recorded pitch (less than 0.15mm) before recording actual signal. Is it for stabilizing the arm or for timing of starting signal?

4. Marker space grooves for interval between bands: pitch per turn is around 1mm (1.6mm max). The marker space should not be located inner than radius 63.5mm (as per IEC98-1987) lest the auto-lift of player should be activated before the end of music groove. 

5. Ending of music groove.

6. Lead-out grooves: when the lead-out pitch is exceeding 6.4mm/turn, the top width of groove shall be increased to more than 75micron according to IEC98(1964&1987).  BS1928-1965 recommended minimum top width 0.004 in (0.10mm) irrespective of lead-out pitch width for fine groove records.  My note: wider top width for wider pitch is safeguard against spiral tracing force especially at the junction from lead-out to finishing groove. Often narrow top width for wide pitch makes the stylus climbing over the groove wall and touching at the label! Usually the first & last lead-out pitch of spiral groove is narrowed more than normal lead-out pitch in order to avoid such accident.  

7. Finishing groove: concentric loop for modern design of records. In the past eccentric loop was designed for 78rpm and early LP records activating automatic shut-off mechanism.

Stylus profiles for LP

About the contours of fine groove and applied stylus, I find two drawings as under. The original sources of these drawings are unknown (left drawing was made earlier than 1955 because same was shown in Itoh's book-1955 while right one was shown in Yamamoto's book-1971).  I suppose it might be originated from Monophonic Fine Groove record before stereophonici era since the applied stylus radius 1mil=25.4micron and top width 2.3mil=58.42micron are common in both drawings. 

The bottom radius of groove is not specified in above left drawing while the maximum bottom radius 5micron quoted in above right drawing seems to correspond with JIS S8502-1973. We should be careful about the minimum and maximum figures in standards since the figures quoted there are specified as independent figures on different phase and not transferable actually in one simple figure or drawing - sometimes simplified drawing is the source/cause of misunderstanding. For instance, groove depth 23.6micron in the right drawing is applicable for top width 51.3 or 51.4 micron and bottom radius 5micron. The height gap between contact point and the edge of land 0.44mil (11.2micron) is applicable for top width 2.3mil (58.42micron) and stylus tip radius 1mil (25.4micron).