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How records are made

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CUTTING THE DISK

Once started on its spiral course, a cutting stylus cannot be stopped without ruining the disk. Everything must be pre-set and double-checked beforehand, from the visual selection and flatness of the disc blank, to the condition of the sapphire cutting stylus, chip suction and all the audio connections and settings. An appropriate size recording disc blank is chosen... usually 14" diameter for a 12" final disc size. A silent groove test cut is made, outside the diameter of the finished disc. This is examined under the microscope to check for correct groove size, and sometimes played back to ensure that the noise level is appropriately low. Sometimes discs are rejected at this stage, or even a cutting stylus might be changed, before things are ready to begin the actual recording.

The vacuum pump is started, tape players are cued to the beginning of the recording, the cutting turntable set rolling, and, when all is ready, the stylus is carefully lowered to the record surface, the fast beginning lead-in spiral is cut, the tape playback is started a turn or two after the spiral has ceased, the audio feed to the disc recorder is enabled, and the record is on its way. Depth of cut is periodically checked through the microscope, and of course the volume levels must be watched even though automatic variable pitch will protect against most instances of overcutting to adjacent grooves, there are still the odd nasty surprises that get past the tape mastering engineers. The running time must be checked at the 1/4, 1/2 and 3/4 way through, to ensure that the disc reaches the desired end point necessary for standardization of the finished product.

At the end of the record, after about two blank revolutions, the final spiral lead-out groove is made, again by speeding up the lead screw of the cutting lathe, either automatically or manually, followed by a lock groove. In earlier times, an eccentric lock groove was added on a special machine designed for this purpose. The master is now done, except that it must be visually examined very closely for flaws... once made, it is NEVER played.

For moving to the processing plant, masters are bolted by their center holes into an elaborate box with separations that keep the actual surfaces from touching; lacquer is extremely delicate and easily scratched. (Masters are conveniently stamped or marked for identification in this manner with a scratching stylus, the marks appearing on every finished disk.)

SPEEDS, GROOVES AND RECORD SIZES

There are only minor differences between records, other than the most obvious of size and speed, from 7" 45 rpm through to the 16" 33 rpm transcriptions once used by broadcasters. The greatest differences, however, are found in the groove sizes. Coarse groove 16" radio transcriptions used a slightly narrower and more closely packed groove than the average 78 "standard", but it is played at 33 rpm. The groove used for LP's and 45's is smaller still, and much more closely packed. The problems of groove accuracy with LP's are greater in all respects, than with the old larger groove, and for a while after the debut of the LP in 1948, there were dire mutterings and groanings throughout the industry that small groove cutting was all but impossible.

After unheralded agonies of experiment and slow experience, the cutting of small grooves became less terrifying, and ultimately, no more trouble in this area than the old, and with minor adjustments to stylus size and depth of cut, any sort of record may be cut on the same equipment.

The record mastering engineers are usually found in the studio environment but the plating, pressing and manufacturing of the actual record is usually done at another location. Once the finished lacquer is in its shipping box we enter a new world, a world of more or less mass reproduction, where the object is the making of many from one.




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