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SUMMER 2018

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Distributor's Link Magazine Summer 2018 / Vol 41 No3

8 THE DISTRIBUTOR’S

8 THE DISTRIBUTOR’S LINK Bengt Blendulf Bengt Blendulf was educated in Sweden and moved to the US in 1974 to start a subsidiary for a Swedish fastener manufacturer. After working as a technical consultant on the faculty of the College of Engineering and Science at Clemson University, he established EduPro US in 1997 to teach highly rated courses in Fastening Technology in the US, Canada, Mexico, Europe and Asia. Being one of the founders, Bengt served as the chairman of ASTM F16.96 Bolting Technology from 1996 to 2006. In 2006 he received the Fred F. Weingruber award from ASTM for “his efforts to promote and develop standards for the fastener industry.” In 2013 he also received IFI’s Soaring Eagle Award for “significant contributions to the technological advancement of the fastener industry”. Bengt is the author of an extensive lecture book, well over 110 articles and “Mechanical Fastening and Joining”, a book published in 2013 by the Industrial Fasteners Institute. He can be contacted through www.edupro.us or by email bblendulf@yahoo.com. FASTENER FRICTION – FRIEND OR FOE? When we are tightening a threaded fastener we are actually working on a rather uphill battle. The moment of force we are applying, also called tightening torque, is to a large extent wasted in overcoming friction. It is generally understood that for a “normal” fastener, where the head size is about 1.5 times the nominal diameter of the bolt/screw, we are wasting about 90 % in overcoming the under-head and thread friction when tightening. This leaves us only a small portion to produce the workable tension in the system. This is how it relates: ....of 100% moment of force or torque: 50% is wasted in the bearing area 40% is wasted in thread friction 10% is producing the preload If we, instead of using a Hex Cap Screw or Socket Head Screw, are using a Flange Screw, where the much larger bearing area give us also a larger friction resistance, we may not get the desired clamp load unless we put in a higher moment of force. In addition, the friction between the internal and external threads will also cause a buildup of torsional stresses in the fastener that will lower the load bearing capacity of the fastener. I leave the torsional issues until later in this article. Let us begin with the preloading issue. If we approach CONTRIBUTOR ARTICLE the tightening (try to avoid the term Torquing even if you use torque as a method) issue first, there are some rather straight forward mathematics available to us. First of all we need to know the coefficient of friction. How do we get a good number on that? The best way is to buy a publication from IFI called “Torque Book for Fasteners”. It is a 30-page book developed by Joe Greenslade when he was the Director of Engineering Technology at IFI. Joe collected information from the industry and made a table showing the nut factors for a variety of lubricants. Since the nut factors were based on a standard size of a Hex Cap Screw, I suggested a conversion factor to get to the actual friction coefficient. This was also done so we can use it also for larger bearing area fasteners like flanged fasteners. The 80 various finishes include also the new engineering class coatings like Dacromet, Geomet, Magni, etc. in addition to the more general surface conditions. Let us now start with the nut factor, sometimes we use the term K-factor. In the following I will use lower case “k” for this factor to follow international standards. Capital “K” is the SI symbol for kelvin, the Thermodynamic Temperature and should not be used in issues related to the tightening of fasteners. The “k” factor is essential for the development of the moment of force (also called torque for simplicities sake). CONTINUED ON PAGE 94

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    THE DISTRIBUTOR’S LINK 59

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    THE DISTRIBUTOR’S LINK 61 AFIXX A

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    64 THE DISTRIBUTOR’S LINK BRIGHTO

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    68 THE DISTRIBUTOR’S LINK Earnest

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    On June 7, 2018, SWD Inc. held a gr

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    74 THE DISTRIBUTOR’S LINK FASTENE

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    76 THE DISTRIBUTOR’S LINK Anthony

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    78 THE DISTRIBUTOR’S LINK Wrought

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    NFDA 50th ANNIVERSARY MEETING & CEL

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    THE DISTRIBUTOR’S LINK 85

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    THE DISTRIBUTOR’S LINK 87 FAR SRL

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    THE DISTRIBUTOR’S LINK 89 ABBOTT-

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    92 THE DISTRIBUTOR’S LINK NORTH C

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    94 THE DISTRIBUTOR’S LINK BENGT B

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    SOLUTION INDUSTRIES LLC SOLUTION IN

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    THE DISTRIBUTOR’S LINK 99 WORDSEA

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    THE DISTRIBUTOR’S LINK 101 WOMEN

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    J.W. Winco, Inc., A Ganter Company,

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    SEFA SPRING CONFERENCE BIRMINGHAM,

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    108 THE DISTRIBUTOR’S LINK CARMEN

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    110 THE DISTRIBUTOR’S LINK ALBANY

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    112 THE DISTRIBUTOR’S LINK COMPUT

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    114 THE DISTRIBUTOR’S LINK MICHAE

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    FASTENER FAIR USA CLEVELAND, OH - A

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    THE DISTRIBUTOR’S LINK 121 FASTEN

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    124 THE DISTRIBUTOR’S LINK BRIGHT

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    fastenerlinks THE DEFINITIVE WEB DI

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    fastenerlinks BRINGING YOU THE FAST

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    fastenerlinks BRINGING YOU THE FAST

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    NFDA 50th ANNIVERSARY MEETING & CEL

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    136 THE DISTRIBUTOR’S LINK JO MOR

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    PAC-WEST 50TH ANNIVERSARY MEETING &

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    THE DISTRIBUTOR’S LINK 141 CROSSW

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    THE DISTRIBUTOR’S LINK 143 ZaGO M

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    146 THE DISTRIBUTOR’S LINK GLOBAL

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    148 THE DISTRIBUTOR’S LINK SOUTHW

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    150 THE DISTRIBUTOR’S LINK BRYCE

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    152 THE DISTRIBUTOR’S LINK ZaGO M

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    156 THE DISTRIBUTOR’S LINK ANTHON

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    158 THE DISTRIBUTOR’S LINK LARRY

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    160 THE DISTRIBUTOR’S LINK ROBERT

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    162 THE DISTRIBUTOR’S LINK MID-AT

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    164 THE DISTRIBUTOR’S LINK LAUREN

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    166 THE DISTRIBUTOR’S LINK SEFA S

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    Earnest Machine is now offering dom

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    THE DISTRIBUTOR’S LINK 171 NORTH

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    THE DISTRIBUTOR’S LINK 173 Suncor

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    MAFDA GOLF & SCHOLARSHIP OUTING APP

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    SFA SPING CONFERENCE & GOLF OUTING

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    NFDA 50th ANNIVERSARY MEETING & CEL

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    THE DISTRIBUTOR’S LINK 181 SEFA S

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    184 THE DISTRIBUTOR’S LINK SPIROL

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    SFA SPING CONFERENCE & GOLF OUTING

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    THE DISTRIBUTOR’S LINK 189

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    advertisers index # 3Q, INC. 84 Spl

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    advertisers index I ISC - INTERCONT

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