. Electric railway journal . effectivediameter of the bolt is less than the actual shank diam-eter; rolled threads, on the contrary, are rolled upfrom the shank, so that the effective diameter and theactual shank diameter are the same, but as the diameterover the threads is greater, holes for rolled bolts haveto be a little larger than for the bolt of the same sizewith cut threads. In chestnut the hole is usually bored a trifle larger,and it is invariably larger in the crossarm itself. Whilethere is little likelihood that the arm will actually besplit, a tight fit generally results in breaking
. Electric railway journal . effectivediameter of the bolt is less than the actual shank diam-eter; rolled threads, on the contrary, are rolled upfrom the shank, so that the effective diameter and theactual shank diameter are the same, but as the diameterover the threads is greater, holes for rolled bolts haveto be a little larger than for the bolt of the same sizewith cut threads. In chestnut the hole is usually bored a trifle larger,and it is invariably larger in the crossarm itself. Whilethere is little likelihood that the arm will actually besplit, a tight fit generally results in breaking out badsplinters on the face, for the bolt should be driventhrough the pole first. Perhaps it would be better to June 21, 1919 Electric Railway Journal 1205 say that it is generally so driven, for some overheadmen claim that if good material is used the bolt willalso require replacement by the time an arm has tobe replaced. Then the advantage of not having to pull the boltthrough the pole to remove the arm quite Bolts BOLTS FOR OVERHEAD LINES* *This and the following line drawings are reproduced from theEngineering Manual of the American Electric Railway Engineer-ing Association. The arm is given a good bearing on the pole by again, formed by making at right angles to the poletwo parallel saw cuts each 1 in. deep at the center, and adistance apart just equal to the depth of the wood between these cuts should be taken out witha broad chisel, and the resulting surface hollowed veryslightly, so that when the arm is bolted on, it firstbears at the edges of the gain, thus preventing rock-ing. If this is properly done, and the width of thegain is such as to give a tight fit, there need be littlefear of any trouble under reasonable loading, but it issuprising how few linemen can really make a good gain. This has led to the development of several typesof patent gain. One of the simplest is a piece ofsheet steel, curved to fit the pole, with lugs to holdthe ar
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