Views
2 months ago

SPRING 2019

  • Text
  • Wifi
  • Manufacturing
  • Continued
  • Products
  • Fatigue
  • Industrial
  • Association
  • Distributors
  • Fasteners
  • Fastener
Distributor's Link Magazine Spring 2019 / Vol 42 No2

26 THE DISTRIBUTOR’S

26 THE DISTRIBUTOR’S LINK Guy Avellon Guy Avellon has been in MRO and Fastener Distribution for over 30 years, in such positions Sales Engineer, Chief Engineer, Manager of Product Marketing, Product Engineering & Quality and Director of Quality & Engineering. He founded GT Technical Consultants where he performs failure analysis, lectures on fastener safety, works for law firms and designs/audits Quality systems. He is a member of SAE, is Vice Chairman of the ASTM F16 Fastener Committee, Chairman of the F16.01 Test Methods Committee and received the ASTM Award of Merit in 2005. Guy can be contacted at 847- 477-5057, Email: ExpertBoltGuy@gmail.com or visit www.BoltFailure.com. WHAT FASTENER DISTRIBUTORS NEED TO KNOW ABOUT WHEEL STUDS AND LUG NUTS - PART 2 In the last article we discussed the various ways wheels were traditionally removed and replaced and how these multiple events will deteriorate the internal threads of the wheel nut. This article will discuss how failures happen and why distributors should not be held responsible. Wheel failures occur on all types of vehicles; passenger cars, light duty trucks and medium to heavy trucks. Many are not reported unless the incident causes serious injury or property loss. The NTSB (National Transportation Safety Board) has stated that in their findings with truck wheels, incidents stem from inadequate maintenance. Basic causes include: failure to follow recommended wheel maintenance procedures, such as using a torque wrench, following proper tightening procedures, using only compatible components, avoiding paint build-up, debris, oil, or rust between the wheel joint surfaces and on fastener threads. Many tire shops have trained their personnel on how to properly prepare and mount a wheel. Unfortunately, there are also those who do not adhere to proper techniques and private mechanics and repair garages have no idea all that is involved. They know how to fix a car, not how to mount a wheel. Impact guns: for example, many times, I’ve heard a mechanic say his impact wrench only puts out 90 pounds. This is not torque output, it is the air pressure of his air impact gun. Shops will have an air supply tank that puts out 120 psi air pressure. When it drops to 90 psi, the compressor kicks in to boost the reserve tank up to 120 CONTRIBUTOR ARTICLE psi again. This is air pressure, not torque. What happens to the output torque of the impact gun between 120-90 psi? If someone is installing the lug nuts on a vehicle, while at the same time another air lift is being used and / or another air wrench is being used, the output fluctuates. None of the wheel lug nuts will have the same applied torque. The common 1/2” drive impact wrench found in all shops has an output torque of between 325 and 425 lb-ft., depending upon model and how new it is. The average wheel nut torque for a passenger vehicle is between 80 – 110 lb-ft., heavy trucks average 500 lb-ft. Since the use of disc brakes on vehicles, auto manufacturers have always stated to use a torque wrench only, as the high-speed impacting of the unregulated air tools can warp the rotors. Impact wrenches look for friction to cause it to stall. If a lubricant is present, the friction between the threads is greatly reduced and thread stripping occurs to the wheel nut and the wheel stud may be taken into yield. Overtorquing leads to a weakened and loose joint as neither problem is visually detectable. The internal threads of the wheel nut will look fine on the outside and the thread pitch of the wheel studs may appear to also be good. The damaged wheel nut may even be able to thread onto the wheel stud but more torque will be necessary to overcome the increased friction between the mating threads than is applied to tighten the joint and increase clamp load. Clamp load is therefore lost even though the proper torque was applied. CONTINUED ON PAGE 108

SHARE A PAGE FROM THIS MAGAZINE

OPTION 1: Click on the share tab above, or OPTION 2: Click on the icon (far right of toolbar) and then click on the icon (top right of the page).

View Archives

SPRING 2019
WINTER 2019
FALL 2018
SUMMER 2018
SPRING 2018
WINTER 2018
FALL 2017
SUMMER 2017
SPRING 2017
WINTER 2017
FALL 2016
SUMMER 2016
SPRING 2016
WINTER 2016
FALL 2015
SUMMER 2015
SPRING 2015
WINTER 2015
FALL 2014
SUMMER 2014
SPRING 2014
WINTER 2014
FALL 2013
SUMMER 2013
SPRING 2013
WINTER 2013
FALL 2012
SUMMER 2012
SPRING 2012
WINTER 2012
FALL 2011
SUMMER 2011
SPRING 2011
WINTER 2011

Copyright © Distributor's Link, Inc. All Rights Reserved | Privacy Policy