Masonry Magazine June 2005 Page. 35
LES,
AMS
ND
TERS
A LEVEL IS A SIMPLE TOOL ONLY SLIGHTLY MORE COMPLEX THAN A TROWEL. The spirit level, much as we know it today, was invented by M. Thevenot in 1661. Many believe bubble levels did not come into wide-spread use until the beginning of the 18th century because the earliest surviving examples come from that time. However records show "levels of the Thevenot type" were used on a French expedition to Madagascar in 1666.
Since they've been around for hundreds of years and haven't changed much in principle over that time, comparing today's level with one from the 1700s wouldn't point up the real difference: the accuracy built in from quality manufacturing, Al Karraker, Director of Marketing for Empire Level Manufacturing in the Wisconsin town of Mukwonago, puts it this way: "Accuracy is our most important goal in making a level. To do this, we consider three components: frame, machining and the vial. Every step of the way, we make sure these are of the highest quality and made with the best equipment and materials"
The Frame
"TO BEGIN," Karraker says, "the durability of components is a major part of making the manufacturing of a product successful. The frame itself must be made to very exacting tolerances- not only to work with our equipment, but for the final accuracy of the product. Then machining is done using high-quality tooling and equipment. These machines certainly cost more, but are well worth it in the quality they provide to the end product."
At Empire, the frame can be aluminum, wood or composite (POLYCAST), Many companies focus on making only wood or metal levels. One of the latter is Master Level of Barrie, Ontario, Don Reid says about their levels, "We make box beam levels using an aluminum alloy heat treated to a hardness equal to T6. That means it's fairly stiff but it's also like a spring - if you bend it, it will flex back. Sure, if you bend it beyond its yield point, it can stay bent a little bit but it can be straightened back. If you bend it too far, it's hard enough that it will break. So if somebody drives over it with a truck it can break. That's beyond its normal use."
To Machine or Not?
KARRAKER MENTIONS machining the level. Reid disagrees: "I don't mill the surface of the top or bottom, although some companies do. What happens when you mill is you're adding work hardening stress to that surface. Unless you clamp the level and stress-relieve it by bringing it up to 300-plus degrees, it can pull and warp. For years people said aluminum levels warp in the sun, but that's not true if they're done right. Another reason I don't machine the surface is because when you're taking a level and putting the level against a block wall or a piece of masonry, it's not a machined, flat surface. We can maintain our straightness within 1/64 of an inch over 36 inches just by using care with the extrusion. All our levels, when they're cut, punched, coded, heat treated or stressed, we go back over them with a dial indicator to check it for straightness within the accuracy we guarantee."
Stabila is a German company with more than 110 years in business. Mike Fraser, President of Stabila's North American operations, with headquarters in South Elgin, III., says, "We machine the reading surfaces of our levels up to 48 inches long. The measuring surfaces of all Stabila levels are very flat and smooth, which is a must if accurate readings are required. The reading surface must be flat and smooth so that it is easily wiped clean and will not hold dirt. We do not mill the surface of levels six feet long and longer because this operation has no value whatsoever and is a cost adder."
Bubble, Bubble
THE VIAL is the heart of any level. Spirit levels feature a slightly curved glass tube that is partially filled with a liquid, usually a colored ethanol - hence the term "spirit"-leaving a bubble in the tube. Ethanol is often used because of its low freezing point, which prevents it from freezing in cold weather. Two notches or marks indicate where the bubble should be centered if the surface is level.
Karraker explains, "The main area of change over the last few years has been in molding, We were able to move from bent glass vials to our new 'Advanced Concentric Molding technique. We are now able to make vials more accurately and with more durability than ever before possible. This technique results in accuracy of 0.0005 inches per linear inch in all 10 working positions."
Empire also introduced its True Blue™ vials featuring dark bands on both ends. This banding strongly enhances bubble visibility.
While Empire molds its vials, other companies do things differently. Fraser of Stabila says: "We form an acrylic compound, an extremely durable material, into solid blocks that are then cut, machined and polished. In this process, the surfaces