Grub screws are often used to secure collets, gears and faucet handles, among other things. Grub screws, commonly known as set screws, do not have heads. They have either a hole for an Allen wrench or a slotted opening for a flat-head screwdriver. Grub screws are just like any other screw, which means they can be difficult to remove. Removing stubborn grub screws is really no different than removing any other screw. All that is necessary is a little bit of lubrication and a lot of patience.
Spray the edges of the grub screw with a penetrating lubricant and allow it to work for 15 minutes. The penetrating lubricant eats away at rust and other corrosives to aid in loosening the screw.
Turn the grub screw clockwise slightly with either an Allen wrench or flat-head screwdriver, depending on the screw. When the screw moves, turn the screw counterclockwise to remove it from the part. The movement clockwise, as if tightening, sometimes breaks the seal any rust may have on the screw.
Insert a center punch into the center of the screw if the screw still does not budge. Tap the end of the center punch with a hammer to create an indentation. This indentation prevents the drill bit from walking as you drill through the screw.
Drill a hole through the center of the screw with an appropriate size drill bit. Most screw extractor kits have directions on what size hole to drill for the various extractors.
Insert the appropriate size screw extractor into the hole, then tap the end of the extractor with a hammer to insert the tool firmly into the hole. Turn the extractor counterclockwise with the handle from a tap-and-die set. The handle fits snugly over the screw extractor. Alternatively, you can use a six-sided socket wrench to turn the tool. Remove the screw from the part.