The main reason hand impacts are better than battery impacts is because when using JIS or philips fasteners the hand impact is driven into the fastener as much as it turns it so it is less likely to climb up out of the fastener. A good solid hammer blow exerts more force than what you can provide from just leaning into it with a power tool (unless you can anchor your feet against a wall or something).
The first thing we used to do though is replace the philips, slot head or JIS head screws with allen heads.
My room mate in the 70's was a motorcycle mechanic and he brought home a busted vessel impact. The end where you hit it had a gaping crack around it and was sprung open. Apparently they broke a few by hammering on them too hard on stubborn fasteners. I bought snap-on which were only $60ish or so. Snap-on bits are whats expensive. I'll always grab a 2 or 3 lb hammer for them too.
The first thing we used to do though is replace the philips, slot head or JIS head screws with allen heads.
My room mate in the 70's was a motorcycle mechanic and he brought home a busted vessel impact. The end where you hit it had a gaping crack around it and was sprung open. Apparently they broke a few by hammering on them too hard on stubborn fasteners. I bought snap-on which were only $60ish or so. Snap-on bits are whats expensive. I'll always grab a 2 or 3 lb hammer for them too.