#9090 Square Plug Gage – Robertson Drive
The #9090 Square Plug Gage is a precision inspection tool designed to verify square recess geometry for screws manufactured to Robertson square drive standards.
Square recess systems, commonly referred to as Robertson drive, are widely used in construction, industrial manufacturing, and OEM assembly applications requiring secure driver engagement and reduced cam-out.
Proper recess geometry is critical to ensure correct driver fit, torque transmission, and long-term assembly reliability.
The 9090 Series functions as a plug-style inspection gage used to verify dimensional conformity of the square recess profile.
Available sizes:
9090-00 – Size 00
9090-0 – Size 0
9090-1 – Size 1
9090-2 – Size 2
9090-3 – Size 3
9090-4 – Size 4
The 9090 Series is ideal for:
• Fastener manufacturers
• Industrial hardware producers
• Construction fastener suppliers
• OEM production lines
• Quality inspection laboratories
Gage probes are heat treated, thermally stabilized, and surface treated to maximize wear resistance and dimensional stability.
Long form calibration certificates provide dimensional verification and traceability to the National Institute of Standards and Technology, NIST.
The 9090 Series ensures accurate and repeatable square drive geometry verification.
1) Standard Compliance
Robertson Square Drive Standards
Inspection Type: Plug Gage Geometry Verification
Drive Type: Square Recess
Calibration: NIST Traceable
2) Inspection Function
The 9090 Series verifies:
• Square recess dimensional conformity
• Driver engagement profile
• Manufacturing tolerance control
• Assembly reliability
This gage verifies recess geometry and does not measure penetration depth.
3) Materials & Construction
Universal’s 9090 Series plug gages feature:
• Hardened precision ground square profile
• Heat treated tool steel construction
• Thermally stabilized body
• Surface treated wear-resistant finish
• Laser engraved size identification
Designed for high-volume industrial inspection environments.
4) Calibration & Traceability
All gages include:
• Dimensional verification
• Long form calibration certificates available
• Traceability to NIST
