NEMA Motor Frame Chart

What it is

A NEMA frame number fixes a motor's key mounting dimensions so motors of the same frame from different makers fit the same base and shaft. NEMA MG 1 sets these dimensions. The frame number does not set horsepower; it sets size. The main dimensions are D (shaft height, from the bottom of the feet to the shaft center), 2F (spacing of the mounting holes along the length), 2E (spacing across the width) and U (shaft diameter).

How to read it

• Integral-horsepower frames (three digits, such as 184T): the first two digits divided by 4 give the shaft height D in inches. 18 / 4 = 4.5 in. The third digit relates to the hole spacing along the length (2F). A higher third digit means a longer base in the same frame size.
• Fractional-horsepower frames (two digits, such as 56): the number divided by 16 gives the shaft height in inches. 56 / 16 = 3.5 in.
• Letters after the number add detail (see chart).

Frame chart (T-frame)

Common suffixes

Key points

• T and U frames are not interchangeable even with the same first digits. Shaft size and some mounting dimensions differ.
• Frame number sets shaft height, not power. The same frame can carry different horsepower at different speeds and enclosures.
• Makers may add their own letters. Check the motor data sheet for full dimensions.

Common mistakes

• Replacing a U-frame motor with a T-frame without checking the shaft and base.
• Ordering a TS short-shaft motor for a belt drive.
• Assuming a C-face motor also has feet.

Governing standards: NEMA MG 1 (motors and generators, frame dimensions); motor maker dimension sheets.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.