If you're having trouble removing a stuck bolt, common advice is to heat the bolt up. But if metal expands when heated, wouldn't heating up the bolt just make it harder to remove? How does heating the bolt get it unstuck?
If metal expands when heated, how does heating a bolt loosen it
boltsremoval
Related Solutions
After cutting the bolt to length, use a stationary grinder instead of a file to clean up your work. With a grinder, it's easy to square up the end of the bolt and apply the chamfer that you want.
Just be careful, especially if the bolt is shorter than the grinder's table. If the bolt is short, use a pair of vice grips to hold the bolt during grinding. And remember that the end of the bolt is going to be very hot after grinding!
Lock nuts and carriage bolts are a bad combination and even worse when trying to use them in material like particle board or MDF.
You could try to use a Tee nut from the monitor side and then simply use a short hex head bolt into the Tee nut.
Best Answer
The answer is surprisingly simple: the bolt expands, but the nut expands more.
What is happening here is good old thermal expansion:
Now, since the nut's radius is slightly greater than the bolt's, and since the increase is proportional to the rest length, the nut expands a little more.
Iron has a thermal coefficient in the 10-5 / K ballpark. It means that for each 1 K increase in temperature you have an increase in size of 10-5: a 1 m rod becomes 1.00001 m long.
If your bolt has r = 1.5 mm, and the nut has R = 1.501 mm, what happens is temperature is increased of 500 K? Well:
As you can see, before heating R - r = 1 μm, while after R - r ≈ 1.001 μm. It increased!
Please note my numbers are quite wild and used just to make an example. I am sure that I got the starting values wrong, but I hope they help to get the message across anyway.