Deciding whether to loosen by hand or impact

[donkmeister]

I recently snapped an M6 bolt.

It was in a cruddy location, and had properly rusted in. After a few hours soaking with PlusGas I was using the tighten/loosen/tighten/loosen by hand approach and suddenly it yielded. Followed by a mare to drill it out.

In retrospect, maybe an impact would have shaken it loose without snapping. I'll never know.

Unfortunately heating wasn't an option due to everything else being in close proximity and no reasonable way to disassemble first.

My question is: how do YOU decide which approach to start with?

[JimM169]

Had exactly the same at the weekend trying to remove the handbrake surround in my daughters Aygo. Plenty of penetrant spray a day or two before hand, lots of loosen/tighten action on the bolt to get it moving and the bugger snapped after a few turns just as I thought I'd got over the worse part!
TBH think I would have had the same result with the impact gun, doesn't really take much to snap an M6 bolt. On larger stuff, the impact probably has a better chance of success

[paintman]

Start off trying as you did.
Suspect an impact would have saved you some time by snapping it off quicker!
If the bolt head shears then I'd be looking at using the mig to weld a washer & then a nut to the remains

Or break out the mig to start with & put a blob on top of the bolt head, keeps the heat more local if you haven't got one of the induction tools - I haven't.

[the cueball]

I always go for some PB Blaster and a breaker bar.

In some cases I'll go for some heat via a butane MAP gas torch.

I don't like using impact tools to loosen bolts.

[ARH]

In all honesty, a stuck M6 bolt is going to snap rather than unwind however careful you are. My advice just snap it off and get it drilled out, will be quick in the long run

[E-bmw]

As other have said an M6 is going to snap anyway, so just go nuclear & leave a plan B for drilling afterwards, or even drilling beforehand as it is shearing anyway.

Impact is only really for bigger stuff, it will just shear M6 sooner than the old on/off shuffle.