Avoiding Over Tightening Issues

Over tightening sounds like a “good problem to have” – many installers feel that tighter is safer. In reality, too much torque on a bolt, screw or anchor can be just as dangerous as a loose fastener. It can damage threads, crush substrates, change preload in the joint and even lead to sudden fracture in service. For overseas buyers, engineers and distributors, preventing over tightening is not only a technical topic, but also a purchasing and communication topic.

In this article we will look at what over tightening really is, why it happens in projects across Australia, New Zealand and other markets, and how you can reduce the risk through design, installation practice and better cooperation with your fastener supplier.

What does “over tightening” actually mean?

In a bolted joint, tightening torque is used to create clamp load (preload) in the bolt. The goal is to reach a certain tension in the fastener so that the joint stays secure under service loads. When torque is too high for the bolt grade, size, lubrication and joint design, several things happen:

  • The bolt may be pulled close to or into its yield point.
  • Threads can stretch and deform permanently.
  • The bearing surface under the head or nut may crush.
  • Concrete or softer base materials can crack around anchors.

Over tightening is not only “the bolt snapped during tightening”. Even when the hardware survives installation, a bolt that has been stretched too far may have less fatigue life and may fail earlier in service. Technical guides on bolted joint design highlight that preload should be controlled carefully, not maximised blindly.

Typical consequences of over tightening

Here are some of the main issues we see when fasteners are tightened beyond their intended level:

  • Stripped or galled threads – Excessive torque can stretch male and female threads until they no longer mesh properly. This can make future removal difficult and reduce load-bearing capacity.
  • Bolt or screw fracture – High-strength bolts, concrete screws and self-drilling screws can snap during installation or later under dynamic loads if the steel has been over-stressed.
  • Crushed washers and surfaces – Washers and clamped parts can plastically deform, reducing thickness and lowering the residual preload in the joint.
  • Cracked concrete around anchors – Many screw bolts and expansion anchors are sensitive to torque. When installers “lean” on the wrench, they can crack the concrete cone or damage the anchor geometry.
  • Loss of gasket performance – In flanged joints, over tightening can damage gaskets and lead to leaks, especially when high seating stress is applied unevenly across the bolt circle.
  • Hidden safety risks – There are real-world cases where structural components have failed because bolts were over-torqued, damaging the connection and reducing capacity.

For buyers and project owners, the hidden nature of over tightening is especially worrying. A joint may look fine during inspection, but the damage is already inside the steel or in the base material.

Why does over tightening happen on site?

Most over tightening problems are not caused by “bad” fasteners. They are usually caused by how the fastener is selected and installed. Common root causes include:

1. No clear torque specification

If drawings or method statements only say “tighten bolts” or “fully tighten anchors” without giving torque or installation method, installers will use their own judgement. Depending on the person and the tool, this can easily lead to large variation in preload and frequent over tightening.

2. Relying on impact tools without control

Impact wrenches and rattle guns are very popular on construction sites, but they can deliver far more torque than required, especially on smaller diameter fasteners. WorkSafe guidance in Australia has specifically warned that using rattle guns without control can result in both under and over tightening of structural fasteners, with serious safety implications.

3. Friction differences (coatings, lubrication, washers)

Torque is converted into preload through friction in the threads and bearing surfaces. If the same torque is applied to:

  • A black bolt
  • A zinc plated bolt
  • A hot dip galvanized bolt with lubrication

…the resulting clamp forces will be very different. The use of hardened washers or lubricants also changes the torque–tension relationship significantly.

4. Mixed materials and soft substrates

In timber, aluminium, plastics and even some stainless sheet metal, the base material itself can be the weak link. Tightening “until it feels solid” can crush fibres, strip pilot holes or deform thin plates. Over time, creep and relaxation can make the joint even looser, tempting installers to re-tighten again and again.

5. Lack of training and feedback

In many markets, new installers learn from colleagues on site rather than formal training. Without torque wrenches, sample testing or supervision, they rarely see the real effect of too much torque on the joint.

How to specify fasteners to reduce over tightening risk

As a buyer or engineer working with overseas suppliers, you can already reduce the risk of over tightening at the design and purchasing stage.

Choose appropriate bolt grades and diameters

Higher grade bolts (for example, structural or high-tensile grades) carry more load but also have less margin before yield. If the application does not need very high strength, a slightly larger diameter in a lower grade may be more forgiving for field installation.

On the supplier side, you can discuss options such as standard hex bolts, T bolts or customized fasteners designed to match your torque tools and joint stiffness. For example:

Use washers correctly

Hardened washers help distribute load and reduce local crushing. In structural bolting practice, appropriate washers are often required under the turned element to achieve reliable preload and protect the base material.

When you specify your bolted joints, consider:

  • Washer hardness and thickness
  • Need for special shapes (e.g. structural washers, tapered washers)
  • Corrosion protection to match the bolt and environment

If you are sourcing washers together with bolts and nuts, combining them in one purchase from a supplier like Linkworld can make it easier to control the whole assembly. See the category for bolts, nuts and washers here: https://linkworldfast.com/product-category/bolts-nuts-washers/

Select fasteners that suit your substrate

For concrete, brick and masonry, torque-controlled anchors and concrete screws have specific installation ranges. Over tightening can reduce their pull-out and shear performance. Technical guidance for screw bolts notes that tight tolerances in the drilled hole and correct torque are essential for reliable performance.

If your project uses concrete fasteners, it is helpful to:

  • Define whether anchors are torque-controlled or displacement-controlled
  • Provide recommended tightening torque for each diameter
  • Use anchors tested for the strength class of your base material

You can explore typical concrete fasteners here:
https://linkworldfast.com/product-category/concrete-fasteners/

Practical tightening methods to avoid over tightening

1. Provide torque values or methods, not just “tighten”

On drawings, specifications and installation manuals, you can support installers by giving either:

  • A target torque range for each bolt size and grade, or
  • A defined tightening method (e.g. turn-of-nut, angle tightening, or calibrated wrench method).

Public resources such as torque charts for imperial and metric bolts can be a useful starting point, but they are usually only guides and must be validated for your joint and surface condition.

2. Use the right tools for the job

Wherever possible, use torque wrenches or hydraulic tools that can be set to a known torque. Impact wrenches can still be used, but ideally with:

  • Calibrated torque control
  • Lower power settings for smaller diameters
  • Clear written procedures limiting their use on sensitive joints

In high-pressure flanges and structural applications, best practice guides recommend tightening in multiple passes and diagonal patterns to reach uniform preload without overstressing any single fastener.

3. Train installers and give simple visual checks

Short toolbox talks can make a big difference. Topics might include:

  • Recognising signs of over tightening (cracked washers, crushed surfaces, thread damage)
  • Understanding that “more torque” is not always safer
  • Using feeler gauges or inspection marks to confirm that joints were tightened in the right sequence

Training can be supported with sample joints assembled in the workshop: one correctly tightened, one over tightened until failure. Letting installers see and feel the difference is often more effective than a long PDF.

4. Build quality checks into your process

On major projects, random torque verification is common. You can specify that:

  • A certain percentage of bolts are checked with a calibrated torque wrench after installation.
  • Any bolt that turns significantly under the verification torque is reassembled.
  • Over-stretched or galled bolts are replaced, not reused.

Where your supplier provides pre-assembled kits or structural sets, you can also request sample tightening tests at the factory to confirm the expected torque range and preload for the actual coating and lubrication.

How suppliers can support you in avoiding over tightening

A good fastener partner is not only shipping hardware; they also help you define what “correct tightening” means for your project. At Linkworld, the team combines in-house cold forming and machining capabilities with long-term partner workshops to cover a wide range of standard and customized parts.

When you discuss over tightening concerns with your supplier, it can be useful to share:

  • Drawings or sketches of the joint, including flange or plate thickness
  • Base material (structural steel, concrete grade, timber type, aluminium, etc.)
  • Required load levels or design standards
  • Preferred installation tools on site (manual wrench, torque wrench, impact gun, etc.)

Based on this, the supplier can suggest:

If your project requires drawing-based components or assembled sets, you can send your BOM and drawings to discuss options: https://linkworldfast.com/contact/ or email info@linkworldfast.com.

Communication tips for overseas buyers and engineers

When working with manufacturers in Asia or other regions, clear communication can significantly reduce the risk of over tightening in the final project:

  • Use simple, unambiguous English for torque and assembly requirements.
  • Attach reference standards or methods, for example “tighten according to AS/NZS structural bolting practice” or “use torque–turn method with final angle of X degrees”.
  • Ask for sample parts and trial assemblies before mass production, especially when joints involve concrete anchors or mixed materials.
  • Discuss inspection and documentation – for critical projects, you may request basic torque–tension test reports from the supplier’s QC team.

This type of communication does not need to be complicated. Often, a short call plus a PDF drawing is enough to align expectations and avoid later problems on site.

Quick checklist: are you at risk of over tightening?

Use this short checklist to review your current projects:

  • Do your drawings show specific torque values or installation methods?
  • Are installers using calibrated torque tools, or only impact wrenches?
  • Have you selected bolt grades and diameters that are forgiving for field work?
  • Are appropriate washers and base plates used under the bolt head/nut?
  • For concrete fasteners, do you provide training and torque limits?
  • Are any joints showing signs of crushed material, cracked concrete or damaged threads?
  • Do you have a simple inspection plan for critical fasteners?

If you answered “no” or “not sure” to several points, it may be time to review your tightening practice together with your engineers, installers and supplier.

Conclusion: aim for controlled tightening, not “as tight as possible”

Over tightening is a silent enemy of many fastener applications. It can damage bolts, anchors and structures long before anyone notices. The good news is that with thoughtful design, clear specifications and practical training, you can significantly reduce this risk.

If you are planning a new project or reviewing your current fastener list, you are welcome to discuss your requirements with the Linkworld team. You can learn more about the company here: https://linkworldfast.com/about-us/ and browse the product range at https://linkworldfast.com/products/. For inquiries, drawings or mixed-item orders, please visit https://linkworldfast.com/contact/ or email info@linkworldfast.com – the team will be glad to support you in finding fastener solutions that are easier and safer to install.

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