In lamp threading, IPS stands for Iron Pipe Size.
It’s a standardized thread system originally developed for iron pipe, but it has long been adopted by the lighting industry for lamp parts because it is strong, consistent, and widely available.
Key Points About IPS Lamp Thread
- Straight thread (not tapered like plumbing pipe threads)
- Measured by nominal size, not the actual outside diameter
- Used on items like lamp pipe, nipples, couplings, swivels, and many lamp components
⚠️ Because IPS is a nominal standard, the actual outside diameter will be larger than the listed size, which can be confusing when measuring.
Male Thread Chart
Starting from the right → 1/2 IPS through 5/16-27 UNS is hollow. All remaining sizes shown are solid.
The number following the dash (–) indicates the number of threads per inch (TPI). For example, 1/4-27 means the thread has 27 threads per inch.
We generally omit the pitch when referring to 1/8 thread, as it is always 1/8-27.
The finial threads at the top of a lamp harp are 1/4-27.
1/4-20 is the most common furniture thread. It is coarser than lamp thread.
Unlike plumbing fittings, lamp parts are not tapered (not NPT). Lamp thread, also known as IPS (Iron Pipe Straight), uses straight/parallel threads, which are equivalent to NPS (National Pipe Straight) threads.
Slip refers to parts with no threads at all.
Taps are used to cut female (internal) threads.
Dies are used to cut male (external) threads.
A reducer decreases the size of a female thread.
A nozzle decreases the size of a male thread.
Female threads are internal (“innies”); male threads are external (“outies”).
Righty tighty, lefty loosey.
" = inches, ' = feet
ID = inside (internal) diameter
OD = outside diameter
Female Thread Chart
Understanding Gender
In this video, we explain lamp parts and gender. Lamp parts include components such as sockets, shades, bases, and wiring. Understanding these parts is essential for repairing or creating custom lamps.
The video explains male and female connectors, how they function, and how to properly match them when assembling or repairing a lamp.
Common issues and troubleshooting tips are also covered.
Whether you're a DIY enthusiast or a professional in the lighting industry, this video provides a clear overview of how to properly identify and connect lamp parts safely and successfully.