Common knowledge among mechanics is the fact that heating up a nut/bolt (especially corroded or rusted ones) will make it a lot easier to remove…..the question is “how much easier“?
For this test we torqued 4 identical grade 8 nuts/bolts (1/2″-13) to the exact same torque spec onto a fixture that was clamped in the vise. To verify the applied torque, we used a Snap-on Techangle Torque Wrench that was set to 100 ft-lbs.
In addition to this, we also ran the test with 3 different scenarios :
- #1 – “Ambient Temperature” = The nuts were torqued to spec and then immediately cooled to room temperature by soaking them with water. This removed all the heat generated by installing the nut — which had heated up the threads.
- #2 – “Super Cooled” = The nuts were torqued to spec and then super-cooled using a can of Dust Off. By holding it upside down (don’t try this at home), the spray cooled all of the nuts/bolts to below freezing temps.
- #3 – “Super Heated” = The nuts were torqued to spec and then super-heated using a Mini Ductor II Inductive Heater. This heated each of the nuts to a very high temperature & we varied the temps to see if it would alter the results — 900, 800, 700, & 600 degrees.
The results were surprising…..all 4 nuts through the 3 different tests ended up requiring LESS torque than the “installed torque” to remove them.
Using the same Snap On Techangle Torque Wrench, we then removed each nut. Since it can also measure torque in reverse, we verified the results on the digital display.
The most torque that was required was with the Ambient (room temp) test — there was a range needed of 88-91 ft-lbs & they had an average at 90 ft-lbs to remove each of the nuts.
Next was the frozen test — the nuts ranged from 87-89 ft-lbs. On average the super-cooled test required 88 ft-lbs to remove each of them.
Finally was the super-heated test. The results did vary a lot more — but that was specifically because heated each nut up with a 100 degree difference between them. Ranging from 67 ft-lbs (high end) to 47 ft-lbs (low end), we averaged out with 59 ft-lbs to remove those same nuts.
So, what does this prove?
It proves that if you heat up a nut or bolt — it 100% absolutely makes it easier to remove! This will be compounded when dealing with rusty/corroded fasteners, and you may see results even more extreme than what we have proven in this test.
As far a freezing them, it was not very effective. Most likely that is due to the fact that both the nut and bolt cooled together — causing them each to shrink slightly. That would explain why those numbers were almost identical to our ambient test results.
To sum it up — heat works. Just be cautious where you use it….that way you will minimize your risk of accidentally catching your vehicle or garage on fire.