How To Loosen Tight Rusted Bolts without Heat, Using Mild Acidic Penetrating Liquids and Rust Dissolvers | Friction and Rusting Explained

How To Loosen Tight Rusted Bolts without Heat, Using Mild Acidic Penetrating Liquids and Rust Dissolvers | Friction and Rusting Explained

Contents:

  • Mechanics of Bolted Joints
  • Mechanics of Moving Joints
  • Conditions which Increase Friction in Bolted Joints Causing Tight and Stuck Bolts
  • What is the Difference between a Stuck and Seized Bolt?
  • Why Penetrating Fluids are Better than Heating in Loosening Stuck Bolts?
  • Metal Corrosion and the Rusting / Oxidation of Iron Explained
  • Rust Removal Methods

Sketch 2 – Bolted Joint_Bolt and Nut Clamped Metal Plate

After some time, bolted metal joints or connections in structural steelwork, machinery, equipment and appliances will prove hard to unfasten (unscrew, loosen or unbolt) as the bolt and nut gets stuck, making it impossible to turn with a torque wrench. Many people will encounter this problem after the long-term use of a machine or appliance, especially if the machine was not maintained properly or lubricated as needed. However, depending on the item, its built state and usage purposes, some joints don’t need lubrication but friction for them to work and hold firmly, for example this is the case in many structural engineering works such as bolted base plates and anchor bolts. Both static and moving joints can have their fasteners or connecting parts stuck for a variety of reasons that are going to be discussed below. In building, many structures have static bolted joints, for example a structural steel portal frame, steel truss, steel floor joists, steel framework ceiling, recessed screw manhole covers, steel gate and palisade fence. In mechanical engineering, most structures are often characterized by moving joints. Examples include vehicles, conveyer belts, grinding mills, escalators, elevators, wind turbine, cranes, hydraulic turbines and a wide range of other industrial equipment and machinery.

Mechanics of Bolted Joints

Before we look at how or why bolts get stuck, we should look at the mechanics of bolted joints to understand the conditions and forces working together to get the fasteners stuck, jammed or freezed. First, we have to differentiate the types of joints available in engineering. As mentioned previously, we have static and moving joints. Bolted joints are static joints. Static joints are non-moving friction joints known in structural engineering as slip-critical joints. The parts being connected together are static. In this type of joint, a greater amount of friction is required and desirable in producing clamp loads and bolt tension during tightening to provide stability and prevent slippage between the connected parts or surfaces.

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