how to remove jammed screw

[gerti]

You might also give your impact driver a shot if you have one around. I had some luck getting nearly stripped stuck screws out that way.

[steve_ma]

thanks for the tips...I had forgotten the heat method. I think I will just go pick up a screw extractor kit. Probably come in handy later, doh!

[jhart]

Have had good luck using the Sears screw extractor. Generally I've found using it in a hand held driver works better than using a drill, as you can turn/bite the impacted screw better.

[steve_ma]

screw extractor took care of it....

[cgallery]

Think of a thin ring. What expands most when it gets hotter? The circumference expands. This results in a equal amount of diameter expansion since C= 2 Pi D. If you do a finite element expansion, (in layman's terms, treat everything as a bunch of tiny pieces whose group behavior dictates the behavior of the large piece), that's what it'll do.

I stand corrected (again). Sorry for doubting you Art.

So one more question may help me keep this straight in the future:

If a 1' square piece of aluminum that has a 1/4" hole in the center has heat applied such that the area around the hole heats considerably, but the rest of the material is heated less (imagine hitting the area of the hole with a heat gun or a torch), then will the hole still enlarge?

[master53yoda]

yes it will still get larger. heat is the result of molecular motion increase, as any portion heats up the molecules move faster and are further apart. the thickness of the metal at the hole will also increase.

this is an interesting aside but i worked on a cryogenic system for a pharmaceutical that was cooled with liquid nitrogen. the heat exchangers were vented through copper pipe. when they first started these units the feed ports on the LN2 where to large and they flooded the heat exchangers and started running the liquid nitrogen up the copper vent stacks. there was a liquid running of the outside of the copper vent stacks that everyone in the shop thought was condensed water. One of the guys reached for the pipe and i yelled at him not to touch it. I had them catch some of the fluid that was running off the pipe onto a piece of paper, it bounced around on the paper just like water on a real hot pan does. I told them that fluid was LN2 that was going through the wall of the copper pipe. at -350f the copper molecules had stopped moving to the point that the LN2 went right through a solid walled pipe. Molecular sieve...... the coppe pipe also had a gold tinge to it and I bet if it was tapped with a hammer it would have shattered just like a glass tube.

[cgallery]

the thickness of the metal at the hole will also increase.

Ahhh. Thank you Art, that helps quite a bit. OTOH, I've apparently forgotten this lesson at least twice already, so I don't know if there is much hope for me.