How to Deal With Stuck Bolts and Nuts
We received quite a number of responses from our recent Spanner Size Chart (Metric-Imperial Equivalents) article.
We thought one of them – from Andrew M, a qualified tradesman -- is so useful that we’ll share his feedback here for everyone to consider.
Is the bolt or nut still too tight?
"Is the bolt still too tight, even when you’re using the right spanner size? The threads might be too rusty.”
If dealing with either bolt or nut, consider the following:
- When undoing tight threads, sockets are superior to spanners and are far less likely to cause damage to the nut or head of the bolt.
- Is the thread possibly left-hand?
- Soak it in penetrating oil such as the Loctite LB 8040 Freeze & Release Penetrating Oil (see Update 3 below).
- Soak it in a rust releasing agent (see Update 1 below).
- Use an impact wrench (see Update 2 below).
If dealing with a nut, you can also try to:
- Heat the nut but not the bolt/shaft.
- Remove the nut by carefully splitting the nut using a drill / cold chisel.
If dealing with a bolt:
- Heat the bolt and then leave it to cool (before trying to loosen it again)
- Just remember that the use of excessive force may damage the threads or cause the bolt material to shear off. Therefore, it may be worth considering calling in a bolt removal specialist before breaking the bolt.
- Bolts that resist all non-destructive efforts to free them can be removed destructively by using drilling, EDM or chemical removal techniques.
Update 1: We previously included WD40 in the list, but following a suggestion from Ian W, we have now replaced it with a proper rust release agent that is the Reducteur H-72. He noted, however, that if WD40 has been used on the rusted item, then the Reducteur H-72 cannot be used.
According to Ian -- who has a mechanical engineering background and worked in both industrial maintenance and industrial construction -- the super releasing agent releases rusted parts in 30 seconds and is best at preventing rust from forming for extended periods before assembly.
He added that the correct procedure is to:
Wire-brush off all loose material on and around the fastener and its surroundings.
Apply the Reducteur H-72 (or any proper rust releasing agent). You only need to apply a very small amount, just enough to wet the area in question.
Wait for about one minute before attempting to undo the fastener.
He says that those who have not tried it before will be “totally shocked to see just how effective this product is.”
He’s been using it for approximately 20 years already, so it must be really dependable.
His suggestion is to oxy-heat the bolt to bright hot red (if it’s steel), then let it cool. You may have to do it twice. He says the expansion(s) will often break the rust bond.
Just keep in mind that heating will weaken (stainless) steel, so it’s a good idea to have a new bolt with which to replace the stubborn one.
(This particularly applies to bolts on vehicle exhaust systems. He explains that the closer the bolt is to the motor -- eg. if it’s in the exhaust flanges -- and the longer they have been there, the rustier and more frozen they can be.)
If you apply an impact wrench, even after copious good quality penetrant (and time), there is a good chance the bolt will snap, which is something you don’t want to happen.
Another sometimes effective solution is to vigorously "tap" the head of the bolt (meaning a really good thump or two) using a long punch/piece of bar and a bolster hammer, or something similarly substantial. He says the jarring often “convinces” frozen/stuck/overtight bolts “to relax”, just slightly, and together with penetrant, it gives you a fighting chance to free the bolt without it snapping.
Update 3: On the other hand, Jack C -- who is a retired aviation engineer -- vouches for WD40 as effective in helping remove corroded/tight bolts and nuts. He says it also doesn’t cause any harm when sprayed on painted finish, chrome, rubber and even PVC-type seats, even when left on for long periods as a corrosion deterrent.
Thank you -- Andrew M, Ian W, Bob H and Jack C -- for sharing your knowledge.
That leaves us with something to think about the next time we try to loosen a stubborn bolt or nut.
By the way, if you have something useful to share, please don’t hesitate to let us know -- best to email email@example.com.