How do UNSCREW-UMS™ work?
Choose an UNSCREW-UMS™ which is a little too small to fit comfortably outside the shank of the screw. The UNSCREW-UMS™ is tightened into a bit brace or a variable-speed drill (moderate to heavy duty cordless is fine). THE DRILL IS RUN IN REVERSE. The UNSCREW-UMS™ uses the broken screw as a guide. Because the screw is too big for the bore of the UNSCREW-UMS™, the UNSCREW-UMS™ must expand. The bevels on the insides of the teeth encourage expansion and the slot permits this to happen. The deeper the UNSCREW-UMS™ cuts, the more it expands, which in turn exerts more pressure on the core of the screw. Sound screws will normally be backed out after the UNSCREW-UMS has cut down about 1/3 of the length of the stub. Badly corroded screws come out in pieces in the bore of the UNSCREW-UMS™. The UNSCREW-UMS™ are reusable, but due to the heat and forces generated, their life spans are limited.
What is the life expectancy?
Expect to remove 5 to 8 screws from wood with one UNSCREW-UMS™ or 1 to 2 screws from fiberglass. Our experience with wood has been from 3 UNSCREW-UMS™ for 1 screw to 44 screws with 1 UNSCREW-UMS™. When the UNSCREW-UMS™ has spread open to the point where it is removing an unacceptable amount of wood, it may be squeezed back together again. Also, UNSCREW-UMS™ can be resharpened.
Does the metal used in fasteners matter?
So far, no; we have removed Brass, Bronze, Titanium, Everdur, Mild Steel, Stainless Steel and Hardened Steel fasteners. To back out hardened screws use an UNSCREW-UMS™ large enough so that the teeth avoid contact with the hardened metal, but small enough so that the threads of the screw will make the UNSCREW-UMS™ expand as it cuts away the wood around the screw.
What kind of fasteners can be removed?
The UNSCREW-UMS™ will remove other kinds of fasteners as well. We have removed common and finish nails, ring nails, boat nails, drift pins, lag screws and bolts with the UNSCREW-UMS™. All are removed using the normal procedure. Boat nails normally come out without any problems, but large ones may come out easier by spot welding a stud onto the nail, adding an extension and using a slide hammer. Bolts in metal are removed by going down inside the fastener. The UNSCREW-UMS™ are not recommended for sweated in fasteners.