Standard Lamp Thread Sizes


Lamp Thread Sizes

: are mostly standardized. It is imperative to know the thread size when replacing any antique lamp parts. List of common lamp threads and there uses provides a quick reference.
  • 8-32 - 5/32" outside diameter, used as holder screws with some glass shades.
  • 1/4-20 - 9/16" outside diameter
  • 1/4-27 - 7/32" outside diameter, used on harp posts & most lamp finials.
  • 1/8 IP-27 - 3/8" outside diameter, very common thread used on table lamps, socket caps, and some finials. Allows electrical wire to pass through pipe.
  • 1/4 IP-18 - 1/2" outside diameter, used on floor lamps, clusters, ceiling fixtures, and floor lamp bases.
  • 3/8 IP - 5/8" outside diameter, used on chandeliers and hanging lamps.


  • Lamp Terminology

  • F: designates a female thread - part is tapped having interior threads.
  • M: designates a male thread - threaded with exterior threads.
  • Watts: Volts multiplied by Amps
  • Amps: Watts divided by Volts
  • Volts: Watts divided by Amps
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