Dimensional characteristics of 33 rpm phonograph records (R.I.A.A.)
Dimensions des disques 33 tours
| Description | 7″ record | 10″ record | 12″ record | |||
| Unit | millimètre | inch | millimètre | inch | millimètre | inch |
| Outside diameter | 174.6 ±0.8 | 6.875 ±0.031 | 250.8 ±0.8 | 9.875 ±0.031 | 1301.6 ±0.8 | 11.875 ±0.031 |
| Thickness | ||||||
| 1. Flush design | 1.9 +0.3/-0.4 | 0.075 +0.010/-0.015 | 1.9 ±0.3 | 0.075 ±0.010 | 1.9 ±0.3 | 0.075 ±0.010 |
| 2. Contour design | See figure above | See figure above | ||||
| Center hole diameter | Same as 10″ | 7.26 +0.025/-0.05 | 0.286 +0.001/-0.002 | Same as 10″ | ||
| Center of gravity | Same as 10″ | 11.1 | 0.437 | Same as 10″ | ||
| Lead-in spiral¹ | ||||||
| 1. Starting | To start at record edge | |||||
| 2. Grooves/inch | Same as 10″ | 16±2 | 16±2 | Same as 10″ | ||
| 3. Contour | The contour to be same as recording grooves | |||||
| Margin diameter | 172.2 | 6.781 | 246.8 | 9.719 | 297.6 | 11.719 |
| Diam. outermost groove at pitch | 168.3 max. | 6.625 max. | 241.3 max. | 9.500 max. | 292.1 max. | 11.500 max. |
| Recording groove contour | ||||||
| 1. Included angle | Same as 10″ | 90° ±5° | 90° ±5° | Same as 10″ | ||
| 2. Bottom radius | Same as 10″ | 0.006 max. | 0.00025 max. | Same as 10″ | ||
| 3. Width – Monophonic | Same as 10″ | 0.056 | 0.0022 | Same as 10″ | ||
| 4. Width – Stereophonic | Same as 10″ | 0.025 min. | 0.0010 min. | Same as 10″ | ||
| Minimum inside diameter | 108.0 | 4.250 | 120.6 | 4.750 | 120.6 | 4.750 |
| Runout of recording grooves |
Same as 10″ | 0.41 max. TIR² | 0.016 max. TIR² | Same as 10″ | ||
| Lead-out spiral³ |
2 to 6 grooves per inch | 2 to 6 grooves per inch | 2 to 6 grooves per inch | |||
| Stopping groove, closed concentric circle | ||||||
| 1. Diameter | 98.4 +0.0/-2.0 | 3.875 +0.0/-0.078 | 106.4 ±0.8 | 4.187 ±0.031 | 106.4 ±0.8 | 4.187 ±0.031 |
| 2. Width | Same as 10″ | 0.08 | 0.003 | Same as 10″ | ||
| Rotational speed ±0.5 % | 33 1/3 rpm | 33 1/3 rpm | 33 1/3 or 45 rpm | |||
| Direction of rotation | Clockwise when observer faces side of record being played | |||||
| Crossover spiral | The number of grooves joining successive bands on a record shall not be less than 16 per inch | |||||
| Strobe discs to download |
→ Turntable Strobe Disc 50 Hz | → Turntable Strobe Disc 60 Hz | ||||
Notes:
1 – In addition, there shall be at least one complete unmodulated groove at recording pitch
2 – This total indicated runout (TIR) measurement is to be independent of recording pitch
3 – The number of grooves per inch shall be so chosen that the spiral contains at least one complete revolution