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[[File:Screw Head - Bristol.svg|frameless|x22px|alt=]] The ''spline socket'' (alternatively known as ''Bristo'',<ref name=mechpractice>Radio Material School, Naval Research Laboratory. (1943). [https://archive.org/details/NAVPERS14004/page/n57/mode/1up NAVPERS 14004 ''Mechanical Practice'']. Washington, D.C.: USGPO. pp. 48, 50, 51.</ref> ''Bristol'',<ref name="USNBP">Bureau of Naval Personnel. (1971). [https://archive.org/details/ERIC_ED132362/page/n20/mode/1up?view=theater ''Tools and Their Uses'']. Washington, D.C.: USGPO. p. 13 (21)</ref>, ''Bristol spline'', ''multiple -spline''<ref name=purchasing>The Bristol Company (June 18, 1962) [https://archive.org/details/sim_purchasing-1933_1962-06-18_52_13/page/137/mode/1up "Why a Multiple-Spline Socket Screw?"] New York: C.M. Business Publications Inc. ''Purchasing''. p. 137</ref> and ''fluted''<ref>National Bureau of Standards. (1942) [https://www.google.com/books/edition/National_Bureau_of_Standards_Handbook/TKwYAQAAIAAJ?hl=en&gbpv=0 National Bureau of Standards Handbook H28, ''Screw Thread Standards for Federal Services'']. pp. 177, 179, 182, 184</ref>) screw drive features four or six [[Rotating spline|splines]].<ref>Oberg, E. Jones, F. Horton, H. (1984). [https://archive.org/details/machineryshandbo0000ober/page/1156/mode/2up?view=theater ''Machinery's Handbook'', 22nd ed.] New York: Industrial Press Inc. pp. 1157, 1159</ref><ref name=B18.3-2003>American Society of Mechanical Engineers (2003). ASME B18.3-2003 ''Socket Cap, Shoulder, and Set Screws, Hex and Spline Keys (Inch Series)''. New York: ASME.</ref> Almost all of the force of the key or driver is applied normal to the sides of the splines. Little force tending to expand the socket is exerted, unlike the hexagon socket design, making the spline socket preferable for fasteners made of lower strength materials and in setscrews due to reduced tendency of the setscrew to bind.<ref name=mechpractice/><ref name="EngineRoom">United States Maritime Service Institute. (1949). [https://www.hnsa.org/manuals-documents/single-topic/engine-room-tools/ ''Engine Room Tools'']. New York: Mast Magazine Association. p. 25</ref> The spline socket is also preferred over the hexagon socket in screws that must be subjected to high driving torque and in applications requiring high reliability of the fastener.<ref name=purchasing/><ref>{{Cite web|url=https://bristolwrench.com/about/|archive-url=https://web.archive.org/web/20161021202644/http://www.bristolwrench.com/about-bristol-wrench.html|url-status=dead|archive-date=2016-10-21|title=About Bristol Wrench Spline Drive Bits|date=2016-10-21|access-date=2019-11-23}}</ref> Compared to the hexagon socket drive, spline socket drives are less likely to strip for the same amount of torque; however, the spline socket drive is not much more strip-resistant than a Torx drive.{{citation needed|date=June 2010}}
A spline socket screw can be driven by any screwdriver designed to drive slotted screws that will fit into the socket such that the width of the blade occupies the major diameter of the socket and the thickness of the blade permits it to fit between adjacent splines.<ref name=Goodwin01>Editors (April, May 1913). [https://books.google.com/books?id=zJU7AQAAMAAJ&printsec=frontcover#v=onepage&q=goodwin&f=false "Goodwin's Hollow Safety Set Screw"] ''Hardware Dealers' Magazine''. pp. 846 V, 865, 1090</ref>
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