The spikes used to fasten T-shaped railroad track to wooden ties have an L-shaped head and a square shank. The bottom of the head is sloped to match the slope of the flange of a rail. The tip is wedge-shaped, not pointed. The wedge is driven into the tie across the grain, that is, parallel to the track.
Its square cross section gives a railroad spike much higher holding strength than a fastener having the same amount of metal but a circular cross section has; roughly speaking, about 50% more. A spike with the wedge driven across the grain will have about twice as much holding power as one driven with the grain. Early experiments showed that pulling out a 9/16″ × 9/16″ spike driven 4¼ inches into dry cedar required on average a force of 857 pounds. In seasoned oak, another experimenter needed 4281 pounds.
Current standards for track spikes define two grades: 1 (soft) and 2 (high carbon). The stronger high carbon spikes must be marked “HC”.
ASTM A65-01. Standard Specification for Steel Track Spikes. For ASTM standards, access www.astm.org, or contact ASTM Customer Service at firstname.lastname@example.org. For Annual Book of ASTM Standards volume information, refer to the standard's Document Summary page on the ASTM website.
The page below is from the catalog of Bethlehem Steel, a major supplier, circa 1957. Notice that the smaller sizes have a different design.
9. Spikes.-Track spikes should be made of good, tough material, so that the head will stand driving down upon the rail flange without breaking off. Both soft steel and wrought iron are the materials used, the latter principally for the reason that old iron rails are still to some extent being worked up into spikes. The Union Pacific R. R. owns a mill, located at Laramie, Wyo., in which a great deal of wrought scrap, including old iron rails, is made into spikes, bolts, angle bars and bar iron.
The standard size of spikes is 9/16 in. square and 5 or 5½ ins. long under the back of the head. For oak and other wood equally hard a length of 5 ins. is sufficient. The weight of a 5½ ×9/16× 9/16-in. spike is about ½ lb. The head is usually made oblong, about, 1 3/16 × 1½ ins., the under side of the same being inclined to correspond to the slope of the top side of the rail flange, which is usually 13 degrees. The standard spike point is wedge-shaped and its length varies from ¾ in. to 1¾ ins. The exact length, within these limits, is unimportant, so long as it is sharp on the cutting edge and not too thinly drawn out. For hard wood a point about twice as long as the thickness of the spike does very well. 1n seasoned white oak ties a long, slim point is liable to bend in driving and crook the spike. Spikes used in fastening rails to longitudinal timbers, as at pit cattle guards, have the point reversed, or turned quarter way around, so as to cut crosswise the grain and not split the timber. To strengthen the spike against wear from the rail, in the neck (a spike so worn is said to be "goose-necked"), it is the practice with some roads to slightly enlarge the cross section just under the head. Such reinforcement should not be made to the front or wearing side, because it would then operate to bend the spike outward when the head is driven down to the rail, and should the spike work up it would stand clear of the rail or permit the rail to spread slightly. If the reinforcement is made to the sides it interferes with facility of claw-bar operation. If reinforced at all the extra metal should be on the back side, but some object to any reinforcernent to that side, on the ground that such would displace wood fiber which would remain out of contact with the spike, thus weakening its back support, should the spike work up.
The plain hook-headed spike of square cross section, above described, is standard practically everywhere in this country, and it is perhaps needless to say that for general purposes it is the best. Numerous attempts have been made to obtain greater lateral resistance, and increased adhesion, by the use of flat spikes, and spikes grooved at the back to give increased frictional surface, but all such experiments seem to have met with little success, and the spike of square cross section has held the field to the exclusion of all others. It was found that flat spikes were easily bent by the thrust of the rail, and spikes grooved to increase the adhesion cut open the fiber in such manner that water easily found its way into the fiber adjoining the back of the spike. Spikes of oblong section are difficult to catch with a claw bar and in hard timber they bend easily in driving.
About the only improvement in the shape of the spike which has come into considerable use has been made in the shape of the point, the aim being to produce a point which will enter the tie without excessive injury to the fiber. The ordinary wedge point is formed in two ways: it may be cut with a die or it may be drawn out by rolling. When made by the former method the point is sharp, but frequently fins are formed on the corners which cause the spike to turn in driving. The rolled point is usually longer but dull or blunt on the cutting edge. The sharper the point the better is the satisfaction both as to ease of driving and in doing less injury to the fiber of the wood. The Goldie spike, made of soft steel, has a wedge point 1½ ins. long, with corners beveled to sharp cutting edges, as shown in Fig. 22. The front side of the spike, as shown in the engraving at the left, is the wearing side. On this side the beveling extends 1 in. above the extreme point and on the back side 7/16 in. high. A side view of the spike is shown at the right hand in the figure. The standard spike of the New York Central & Hudson River R R., for Carolina pine ties, is patterned closely after the standard spike of the Pennsylvania R. R., which is made of soft steel, is 5½ ins. long under the head, 9/16 in. square, in section, and has a rolled wedge point 1¾ ins. long, blunted on the extreme edge. The spike used by the New York Central company differs frorn that of the Pennsylvania company by being pointed at the tip on the Goldie style. The corners of the wedge on the front side are beveled for a length of 3/8 in. and on the back side 3/16 in., as shown in Fig. 23. In other respects the spike is exactly like the standard of the Pennsylvania road, having a neck enlarged on the side next the flange of the ra�l, the thickness front to back being 11/16 in. The head is 1½ ins. long and 1 5/16 ins. wide. The standard headblock spike of the Pennsylvania R. R. is like the standard rail spike except that it is 7 ins. long. The Diamond spike, shown in Fig. 24, has a gouge-shaped point, the face on the rail side of the point being convex, while on the back side of the spike (right-hand engraving) the face of the point is grooved. Screw fastenings are discussed in a later chapter.
W. M. Camp.
Notes on Track Construction and Maintenance.
Chicago: self-published, 1903.
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Last revised: 20 November 2010.