1. Difference between Metric and Fractional System

Track plate bolts and nuts are categorized into metric and inch system. Metric bolts are measured in millimeters(mm) and threads are marked with M, while inch blots are measured in inches and marked with(‘Φ’)

• Metric bolts: in millimeters(mm), thread are marked with M, pitch is marked in millimeters(mm), pinch is marked in millimeters(mm), and the length marking only calculates the length below the head, excluding the height of the head. Such as M20 × 1.5 × 55 that is, the nominal diameter of the thread is 20mm, pitch d = 1.5mm, length l = 55mm. Thread accuracy level is usually 6g, such as M20 × 1.5 – 6g, that is, the nominal diameter of the thread M20mm, pitch d = 1.5 mm, the thread is 6g.
• Metric nut: Diameter DФ is in millimeters, marked with M, pitch Thread is also in millimeters (mm) as a unit, marked with d. Such as M20 × 1.5-6H (S28 × H21) that is, the nominal diameter of the thread for the M20mm, pitch d = 1.5mm, the side of the nut and the side of the width of the S28mm, the thickness of the nut L21mm, thread accuracy level of 6H.
• Inch Bolts: Inch Crawler plate bolts are made in inches(in),indicated by(”),i inch is equal to 25.4mm, such as 1/2”, 5/8”, 3/4”, 7/8”,1”,1-1/8”, etc., and the threads are Fine Thread, labeled with UNF. PichThread is expressed i units of how many threads per inch, such as UNF-18, UNF-16, UNF-14, UNF-12, etc. British thread with a few minutes of several marked, such as 3/4” – 16UNF × 2-9/16” that is, the diameter of the thread DiaФ for 3/4”(3/4 × 25.4mm that is, Ф = 19.05mm),Pitch Thread for 16UNF(1” has 16 fine threads), the length of 2-9/16”(2-9/16 × 25.4mm that is, L = 65mm). Length L is calculated below the head only, not including the head height.

2. Measurement Methods

• Metric pitch can be measured using vernier calipers or a 60° angled thread plate.
• Inch pitches can be measured by setting the vernier caliper at 25.4 mm and counting the number of threads in inches, or by using a 55° angled threaded plate.

Though the bolts of excavators and bulldozers are small, the impact on their mechanical performance and safety cannot be ignored. By choosing our screw products,you are choosing safety, reliability and efficiency. HOK is committed to be your preferred brand of construction machinery parts to protect your equipment.