Changing your tyres is something you need to do by law and so visiting your local tyre shop for a tyre or two is as common as having a hair cut.
A straight forward job majority of the time and in all honesty its something even the most amateur car DIY enthusiast could do themself.
Easy in, Easy Out, Job Done…
The problem is when things go wrong or theres some issue. Now obviously if there is an issue its either your fault, or third party or the mechanic. In the first two cases its fair for you to just accept this and pay for the additional work. If the mechanic caused some damage or issue then they should cover the cost of repairs or give a significant discount. but just going by experience and other peoples stories we know this is most likely not going to happen. In most cases even if its the mechanics fault they will tell you its your fault. They will not, as professionals and adults, take any responsibility for their actions. Mistakes can happen…
Cross threading occurs when the mechanic tries to put a wheel nut back on using a machine but with excessive force and an incorrect angle. This then means the nut catches some of the threads on the end of the stud and damages them. Because the nuts are supposed to go back on by hand and straight on. But alot of tyre shops get in the habit of just ramming the nuts back on with the machine at high speed to save time and due to lack of care.
Once the stud is cross threaded the nut will not go back on no matter how hard you try. Buying a new nut will also not resolve the issue.
The solution for a cross threaded stud
In most cases if the wheel hub has male studs, you can buy new studs individually from the dealer or online car part shop like AutoDoc.
If they damaged the wheel nut while trying to put it back on to the damaged stud, you will likely also need a new wheel nut. You should be able to pick up a replacement stud and nut for under £15.
You should now be able to find a competent mechanic at a local garage or tyre shop to hammer out the damaged wheel stud and fit in the new one. It should not really take more than an hour.
If you feel upto it and have the right tools you can have a go yourself as shown in this video. But you should always take care with car DIY and seek professional advice or the car manual first.
If possible always try keep an eye on your car while work is being carried out on it. When they take off and put your wheels back on, if you would ever need to take the tyre(s) off yourself then tell them to tighten the nuts by hand, otherwise there is 0% chance you can remove any nut if you ever breakdown or have puncture. Ideally studs and nuts should be greased to prevent corrosion and damage due to weather.
You can read up on how to remove over tight or rusted wheel nuts here.