Why Is the Hole in a 45 RPM Record So Big?

08 Jan 2015

Why is the hole in the middle of a 7-inch single so big?  Believing that consumers didn’t want 22 minutes of music per side as they were getting with Columbia’s new 33 ⅓ REMP album, RCA went with the tried-and-true one-song-per-side format.  

The discs were originally meant to be stacked on the thick spindles of RCA-manufactured phonographs.

The larger hole was necessary to (a) allow the disc to slide more easily down the spindle; and (b) more evenly distribute the torque exerted on the record when it dropped onto the turntable and needed to speed up to 45 RPM instantly.  Engineers found that these forces would fray a small hole, make it go out of round and cause it to wobble as it rotated.  It was all simple physics, really.

And what do you call that plastic thing that you stick in that big hole so you can play a 45 on a regular thin turntable spindle?  A 45 RPM adapter.  A little disappointing, no?

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