How to Reduce Maintenance Costs by Strengthening Component Bonds

Typically, we tend to compartmentalize budgets for replacement parts and labor when it comes to maintenance spending. And that’s not unreasonable; these are the most visible expenditures. But what doesn’t quite streamline in the numbers is the less noticeable cost of vibration: the slow, relentless micro-movement that loosens existing joints, accelerates natural wear, and eventually raises the necessary replacement of components.

Why mechanical fits underperform

For example, press-fit and shrink-fit assemblies have been used in various applications for many years, and still are. However, when two machined surfaces are assembled together, they do not make full contact. In most cases, only 20-30% of the surfaces actually touch because small peaks and valleys are left behind in the machining process. Another similar phenomenon occurs during vibration, but on a smaller scale: the assembled machining surfacing begins to move against each other. This movement creates a corrosion process called fretting corrosion, because microscopic particles are loosened in the interface and then oxidized. The result is that the joint becomes less tight over time, but the metal hasn’t failed.

Do nothing and time is not your friend in these cases.

What chemical bonding actually does

Retaining Compounds are anaerobic adhesives – they cure in the absence of air, specifically in the presence of metal ions. When applied to a shaft-to-housing interface before assembly, they flow into every microscopic void and cure to a rigid thermoset solid. The result is 100% surface contact across the entire bond area, not the 20-30% you get from a press fit alone.

That contact matters for two reasons. First, it distributes load across the whole surface, eliminating the stress concentrations that cause fatigue cracking. Second, it removes the micro-movement that causes fretting corrosion. No movement means no oxidation at the interface, no loss of preload, and no progressive loosening over time.

The sealed interface also stops fluids from migrating along the joint. Internal corrosion – the kind that seizes components together and makes future disassembly brutal – typically starts with fluid seepage into an imperfect mechanical fit. Chemical bonding closes that path before it opens.

The tolerance tolerance trick

Here’s a point that often goes unremarked: with a chemical-mechanical hybrid joint, you simply don’t require the same level of machined tolerance that you do with a pure press fit. A retaining compound with good gap-filling capability will tolerate bore-to-shaft clearances that would be taboo on a purely mechanical design. Loose tolerances mean faster machining, fewer scrapped parts, and cheaper components – with no implication for joint performance.

For maintenance engineers working on legacy kit, this is highly relevant. Worn housings or shafts that have worn beyond their original spec needn’t be replaced or necessarily restored at great cost. If the amount of wear falls within the gap-filling capability of the compound, the joint can be renewed by simple cleaning and correct bonding. That’s a whole heap of maintenance budget saved on elderly equipment.

Matching the compound to the job

Retaining compounds are not all created equal, and one of the easiest places to make a costly mistake when it comes to maintenance is assuming one is ready-to-use on whatever parts you’ve got. Here are the two biggest things that can go wrong: Steel activates anaerobic chemistry easily – but aluminum is less active and "inactive" alloys won’t work at all without assistance. If you don’t get "full cure", all the numbers for the compound are null and void. Most formulations that are intended to work with a variety of materials include a primer or activator that makes it work, but they all carry slightly different recommendations. It is also possible to get a "partial" instead of a full cure if you stray very far from the recommended gap-filling capability and also temperature range where the cured product will live. Most if not all datasheets will make the claim that a poorly prepared or cleaned surface will also lead to a partial cure, which again just winds you up needing to take it back apart in under a year. Just don’t get it wrong.

Downtime is the real maintenance cost

Repairing malfunctioning equipment after it has failed is far more expensive than it seems. The cost of the repair is just the tip of the iceberg; there’s also the lost production, potential damage to the process and other equipment due to unexpected downtime and the cumulative cost impact of operating equipment at less than design output or quality while waiting for replacement parts.

The metric that truly represents equipment health is mean time between failures (MTBF). Improving that KPI by moving small quantities of consumables like retaining compounds out of your stores and onto the line is one way to break the vicious cycle of failure, depletion and financial loss. With enhanced MTBF, the benefits will compound over time. Flawless production will become more frequent, and you will have more time and space to tackle the next weakest link in your production chain – reducing breakdowns still further.