I am re assembling a swing set made of pretty hard wood. My electric drill won't drive the screws in all the way and I have to try to use plain screwdriver. I don't want to strip the heads though. Is there a good lubricant to use? Is spit the best?
A good lube is beeswax. It lubes the screw, but does not retain moisture. I have also been known to use a stick type of teflon, used for lubing drawer guides. Or a chunk of paraffin is fine too.
You don't want to add water, so spit is a poor idea. Why encourage the screw to rust???? This is the same reason why soap works poorly. Soap is hydrophilic. Soap actually draws moisture to the screw, causing it to rust away prematurely, so a BAAAADDDDDD idea.
Drilling a pilot hole is often a help, but don't make the hole too fat, or the threads won't bite. I'll often go considerably smaller than the root diameter of the screw. Just a small pilot hole is often adequate in wood, unless one is working in a very hard wood.
Finally, if a screwdriver fails, I often resort to a brace, a hand held drill from the antique bins. Just check a hex bit into the drill and off you go. Even better, I keep my brace fitted with a quick connect for 1/4 inch hex bits always at hand.
I keep one of these tools always on the wall of my shop. It will drive a screw quickly into wood, with enough force to twist the head off most screws if I overdo it. But you also have perfect control over the torque. And the nice thing is, the battery never dies, it needs no extension cord.
Ief the swing set was in the weather it is possible that the hardware may have rust on them the rust could increase the resistance making it tougher to drive them in. Gunner soap idea is worth trying along with some new hardware and a bigger drill.