Ice screws evolved from ice pitons, which were extra-long, blade-type rock pitons with holes, notches, or bulges to increase their grip in ice. After World War II, climbers experimented with new designs that featured a greater shaft area to decrease the load per square inch on the ice and more holes to help the shaft freeze into the slope.
When ice screws first appeared in the early 1960s, enthusiasts claimed they would revolutionize ice climbing, bringing security to the slopes. Critics scoffed that the screws weren't much better than the older ice pitons. This proved particularly true of the lightweight, relatively weak "coat-hanger" ice screw, rarely used today. But ice screws continued to improve and now are considered reliable leader protection (fig. 14-9).
The modern tubular ice screw is the strongest and most reliable design. Commonly 7 to 9 inches long (18 to 23 centimeters), this screw works well in temperatures of both winter and summer. It is relatively easy to screw in and to screw out, with some models including a built-in ratchet for faster placement and removal. The hollow design minimizes fracturing of the ice by allowing the displaced ice to work itself out through the core of the screw.
After the screw is removed, ice inside the core must be cleaned out immediately or it may freeze to the interior, making the screw temporarily useless. The interior of some ice screws is slightly conical, permitting easier ice removal. If ice freezes to the inside, push it out with a length of stiff wire.
The shape and size of an ice screw have a great bearing on its strength. A large-diameter screw supports more weight than a smaller-diameter screw of the same length. A tubular screw holds a greater load than a solid one.
Another type of ice screw is hammered into place, but screwed back out. This type—developed in an attempt to make an easy-to-place and easy-to-remove screw—is available in both solid and tubular versions.
The solid versions can offer good protection in water ice at temperatures below freezing, but are less effective in other forms of ice and at higher temperatures. Melt-out is sometimes rapid because of limited thread displacement and, under load, they tend to shear through the ice. They can break
if they aren't hammered in all the way, and they are sometimes tough to remove.
Hollow-core versions of pound-in, screw-out designs have the advantage of allowing the displaced ice to come out through the core instead of being forced aside by a solid screw. This design, with its small threads, can be placed with a series of light blows and removed relatively easily by unscrewing or by levering out with an axe pick. It works best in hard ice, but can be unreliable in temperatures above freezing.
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