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Starrett Micrometer Ball Attachments: Improve contact accuracy for micrometers

Starrett 247D Micrometer Ball Attachments, 0.200" Ball Diameter, .250" Diameter Anvil And Spindle, Inch
4.7
[Snap-On Installation]  Snaps onto anvil or spindle; allows two attachments to be used together.
[Hardened Ball Contacts]  0.200" hardened balls provide durable, reliable contact with anvil and spindle.
[Free-Moving Retainer]  Balls move freely in retainer for consistent, positive contact.
[Measurement Adjustment Required]  Subtract 0.200" per ball from micrometer readings for accurate measurements.
[Broad Compatibility]  Fits Nos. 216, 231, 436.1, 733, 734, 1212, 1230 and 0.250" anvil/spindle micrometers.
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Measuring accessories that deliver repeatable spherical contact for micrometer readings, Starrett Micrometer Ball Attachments. Ideal for engineers and hobbyists who need confidence when measuring curved or fragile surfaces. Are these attachments compatible with common micrometer models and simple enough for everyday workshop use?

⚡ At a Glance
  • Contact Accuracy: Hardened 0.200" balls ensure stable point contact and repeatable readings
  • Best for: Precision machinists and hobbyists needing reliable spherical contact on odd-shaped parts
  • Not ideal for: Micrometers without 0.250" diameter anvil or spindle, or flat-surface measurement tasks

Hardened 0.200" diameter balls sit in retainers and snap onto anvil or spindle ends. Subtract 0.200" for each ball used from the micrometer reading to obtain the true measurement.


Consistent, repeatable contact – with hardened 0.200" ball retainers

Balls are hardened, measure 0.200" in diameter and move freely in the retainer to secure positive contact with anvil and spindle. Free movement permits the ball to seat against curved or uneven surfaces while the retainer keeps alignment.

Stable contact reduces measurement variation, so repeated checks match closely. Particularly useful for batch work and quality checks where consistency matters.

Quick attachment and flexible use – with snap-on anvil or spindle fitting

Attachments are easily applied by snapping on to the end of either anvil or spindle, permitting two attachments to be used together for opposite-ended contact. The snap-on design requires no permanent modification to measuring equipment.

Fast changeovers speed up workshop workflow and allow on-the-fly adaptations for different tasks. Dual-attachment use enables measuring between two spherical points without additional fixtures.

Accurate final readings when compensated – with clear diameter correction

The diameters, 0.200" of each ball used, must be subtracted from the micrometer reading to obtain the actual workpiece dimension. The specification for 0.250" diameter anvil and spindle compatibility is provided for correct pairing.

Awareness of the subtraction rule prevents systematic measurement errors. Suitable for users who will apply the correction as part of standard measuring procedures.

✨ The 4 Key Reasons for Starrett Micrometer Ball Attachments
  1. Hardened 0.200" balls – Improve repeatability across multiple measurements
  2. Snap-on attachment – Enables quick fitting to anvil or spindle without tools
  3. Dual-attachment compatibility – Measure between two spherical points without extra fixtures
  4. Clear subtraction rule – Prevents systematic errors by compensating 0.200" per ball
📋 Technical Details at a Glance
  • Category: BISS
  • Product Type: Micrometer ball attachments
  • Ball diameter: 0.200"
  • Anvil/Spindle diameter: 0.250"
  • Attachment method: Snap-on to anvil or spindle ends
❓ Frequently Asked Questions

Q: How do the attachments fit micrometers?

A: They snap on to the end of either anvil or spindle, allowing quick attachment without tools, and two attachments can be used together.

Q: Do micrometer readings change when using the balls?

A: Yes, subtract 0.200" for each ball used from the micrometer reading to determine the true workpiece measurement.

Q: Which micrometers are compatible with these attachments?

A: Compatible with micrometers listed as Nos. 216, 231, 436.1, 733, 734, 1212 and 1230, designed for 0.250" diameter anvil and spindle.

🏆 Our Verdict

The Starrett Micrometer Ball Attachments suit engineers and hobbyists who need dependable spherical contact for measuring curved or delicate parts. Hardened, free-moving 0.200" balls and a snap-on fit deliver repeatable contact and simple, reversible installation. Robust construction and clear correction guidance make them a practical, long-lasting addition to any precision workshop.