Starrett Lock Bolt Assembly for 4″ Square Center Heads PT99021 Part

Description

Product Overview

The Starrett PT99021 lock bolt assembly is a precision‑engineered component designed to fit 4″ square and center heads commonly used in industrial machinery and scientific equipment. Crafted from high‑strength alloy steel, the bolt offers exceptional durability, resisting wear, corrosion, and the high‑stress cycles typical in heavy‑duty applications. Its dimensions—6 x 3.5 x 0.3 inches and a weight of just 0.8 ounces—provide a compact yet robust solution that integrates seamlessly with existing Starrett hardware. The assembly includes a hardened locking mechanism that maintains tension and prevents loosening under vibration, ensuring consistent performance over the product’s lifespan. With a best‑seller rank of #27 in the Lock Bolts subcategory, this part has earned a perfect 5‑star rating from verified customers, reflecting its reliability and ease of installation. Manufactured in the United States, the PT99021 embodies Starrett’s 140‑year legacy of precision tooling and quality craftsmanship.

Usage

This lock bolt assembly is ideal for a wide range of industrial and scientific environments, including manufacturing lines, laboratory equipment, CNC machines, and heavy‑duty tool assemblies. Professionals such as maintenance technicians, mechanical engineers, and skilled tradespeople will appreciate the bolt’s straightforward installation process—simply align the square head with the corresponding socket, insert the bolt, and engage the locking mechanism. The design accommodates both manual and powered tools, making it suitable for rapid field repairs as well as controlled shop‑floor assembly. Because the bolt is compatible with Starrett’s 6″ square head accessories, users can confidently replace worn or damaged components without the need for additional adapters or modifications. Its heavy‑duty construction ensures that it can withstand high torque loads, making it a reliable choice for applications that demand consistent clamping force, such as press machines, hydraulic systems, and precision measurement devices.

Why Choose Us

Choosing the Starrett PT99021 lock bolt means selecting a component backed by a century‑plus reputation for engineering excellence. Each bolt undergoes rigorous quality control testing, including tensile strength verification, dimensional accuracy checks, and corrosion resistance assessments, guaranteeing that you receive a part that meets or exceeds original equipment manufacturer specifications. The bolt’s American‑made origin ensures adherence to strict manufacturing standards, while the use of top‑tier materials provides long‑term reliability even in the harshest operating conditions. Additionally, Starrett offers responsive customer support and a comprehensive warranty program, giving you peace of mind that any concerns will be addressed promptly. By investing in this precision replacement part, you reduce downtime, avoid costly equipment failures, and maintain the performance integrity of your critical machinery.

Key Features

• Heavy‑duty alloy steel construction delivers lasting strength and wear resistance.
• Precision‑engineered square and center head fit ensures seamless integration with existing Starrett tools.
• Hardened locking mechanism prevents loosening under vibration and high‑torque conditions.
• Compact size and lightweight design simplify handling and installation in tight spaces.
• Backed by Starrett’s U.S. manufacturing quality and responsive after‑sales support.

FAQ

What size head does the PT99021 lock bolt fit?

The bolt is designed for 4″ square and center heads, matching Starrett’s standard 6″ square head accessories for a perfect fit.

Is this lock bolt compatible with older Starrett equipment?

Yes, the PT99021 is a direct replacement for original Starrett lock bolts and works with legacy equipment that uses the same square head dimensions.

Can I install the bolt using power tools?

Absolutely. The bolt’s design accommodates both manual wrenches and powered torque tools, allowing for quick and efficient installation.

What warranty does Starrett provide for this product?

Starrett offers a limited warranty that covers manufacturing defects for a period of one year from the date of purchase.

How does the locking mechanism prevent loosening?

The built‑in locking feature engages when the bolt is tightened, creating a self‑locking action that resists vibration‑induced back‑off, ensuring a secure connection over time.