Galling

Galling or Cold Welding is alive and well and may be experience by some. Joe Greenslade identifies the problem: “A few times each year we receive calls from fastener suppliers who are in conflict with their customer over the quality of stainless steel bolts and nuts. The customer’s complaint is that during installation the bolts are twisting off and/or the bolt’s threads are seizing at the nut’s thread. The frustration of the supplier is that all required inspections of the fasteners indicate they are acceptable, but the fact remains that they are not working”

Thread galling is most common with fasteners of stainless steel, aluminium, titanium and other alloys that self-generate protective oxide surface film.

Greenslade Points out: “During fastener tightening, as pressures builds between the contacting and sliding thread surfaces, protective oxides are broken, possibly wiped off, and interface metal high points shear or lock together. This cummulative clogging-shearing-locking action causes increasing adhesion. In the extreme, galling leads to seizing – the actual freezing together of the threads. If tightening is continues, the fastener can be twisted off or its threads ripped out.”

Simply put, Galling occurs when applying too much rotational speed and torque while tightening or undoing screws of these metals resulting in, the nut/threads bite, seize or break. The smaller the size the easier to replicate this and the lower the speed and torque needed to avoid Galling.

Most of us have never heard of Galling. Many are more familiar with automotive sizes fasteners and have limited experience with stainless and alike. Hence when presented with small and micro-screws, can become quite excited and approach the fasteners with force and torque based on prior experience and more appropriate to automotive examples.

Galling and cross threading are some common results of an overzealous application of a driver. This does happen and we have experienced this occasionally. Like a kid who is overly keen to eat the next slice of pie, gets stuck in his throat and the happiness soon ends. As one cook put it: “low and slow”.

In our experience, small fasteners need to be approached slowly, with respect and care. Overly zealous action on watch sized screws can result in galling, seizing and threat damage.

This technique may seem counter intuitive, but it has worked for us: slowly insert the screw until it stops; start turning anti-clockwise; you will feel the thread bed in (albeit in reverse); when you feel this bedding, slowly reverse the rotation and turn the driver clockwise; it should have found the thread channel and action should proceed smoothly and easily; if it does not proceed easily, STOP and reverse the rotation – it may take several attempts to align the threads until the progression is easy and smooth; proceed slowly; when you feel the screw bottom – stop; do not over tighten.

Sometimes it takes what seems like an eternity to align the threads…but patience will result in success and undamaged threads.

If one feels that one’s activity (e.g. using percussion equipment or extreme lifestyle) will cause screws to work out, wipe the screw clean with methylated spirit (or similar) and coat the screw threads with Loctite 222.

We use Loctite 222 on the screw bars that attached the SEL to the watch, but not on the bracelets (that generally are subjected to less rotational movement). If you regularly change bracelets and bands we highly recommend you get a small bottle of Loctite 222.

Shit happens and if this happens to you (and we hope not) we will do all we can to assist.