Starrett 247D Micrometer Ball Attachment 0.200" Diameter Balls for 0.250" Anvils & Spindles

The Starrett 247D Micrometer Ball Attachment is a precision accessory designed to extend the versatility of your outside micrometer. Featuring hardened 0.200" (5 mm) diameter balls, this attachment snaps securely onto the end of either the anvil or spindle, enabling accurate measurement of curved, rounded, and irregular surfaces that flat-faced micrometers cannot reliably contact.

Ideal for measuring the wall thickness of tubing, split and full bearings, sleeves, and other parts with rounded surfaces, the 247D is a practical addition to any precision measurement setup. When using a ball attachment on both the anvil and spindle simultaneously, note that the combined ball diameters must be subtracted from the micrometer reading to obtain the true measurement.

Key Features:

• Hardened 0.200" (5 mm) diameter ball for precise contact on curved surfaces
• Designed for micrometers with 0.250" diameter anvils and spindles
• Ball moves freely in the retainer, ensuring positive, consistent contact with the anvil or spindle
• Snaps easily onto either the anvil or spindle — no tools required
• Two attachments can be used simultaneously (one on anvil, one on spindle)
• Compatible with Starrett Series 216, 231, 436.1, 733, 734, 3734, 1212, and 1230 micrometers
• Made in the USA

Specifications:

• Ball Diameter: 0.200" (5 mm)
• Fits Anvil/Spindle Diameter: 0.250"
• EDP Number: 51177
• Manufacturer Part Number: 247D

Starrett has been the standard for precision hand tools since 1880. The 247D ball attachment is built to the same exacting tolerances as Starrett micrometers, delivering reliable, repeatable results in demanding shop environments.