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Summary: max. torque with a screwdriver

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  • Summary: max. torque with a screwdriver

    Thanks to everybody who replied to my question.
    To summarize:
    - Order of magnitude = 5 to 10 Nm
    - Biblio refs = many in the ergonomy field plus the NASA Anthropometric
    source book
    - But most important ... it is a wrong question because it depends by many
    factors (one for all the handle). As usual below are reported all the

    thanks again


    ps: I left the reply of Paolo de Leva in Italian so you can practice with
    our beautiful language

    **************ORGINAL REQUEST*******************
    Dear All,
    we are testing a two part device. The two parts are connected with a screw
    which should be tightened by the surgeon with a screwdriver.

    Does anybody knows what is the max. torque an average man can produce with
    a screwdriver? A biblio reference to be cited would be great. My medline
    search was inconcludent; I guess I am not using the right keywords .......


    From: Geo4PL

    We've done some testing here and found that around 60 to 70 in-lbs is
    typical but that depends on your screw/tool interface.

    George Iwanski

    You should ask a car mecanician. They have tables of such data. Bye.

    Benvenuti Jean-Francois
    Laboratoire de Genie Medical
    Swiss Federal Institute of Technology of Lausanne PSE-EPFL
    CH-1015 Lausanne Switzerland.
    tel: ++41 21 693 83 38
    fax: ++41 21 693 83 30
    From: Dann L Chow


    You might be able to find something if you look in ergonomics journals
    instead of medical ones...actually, let me have a quick look for you...OK,
    here's one:

    D.J. Habes and K.A. Grant
    EMG study of maximum torques and upper extremity muscle activity in
    simulated screwdriving tasks
    International Journal of Industrial Ergonomics v20 n4 Oct 1997, p339-346
    I don't have the article, but good luck finding it. DC

    Dear Marco,
    How big is the handle? That will clearly be the limiting factor in
    generating torque. My guess is that you will want to limit, rather than
    augment, whatever forces are applied manually (speaking as a female who can
    strip aluminum screw threads on her bicycle without breaking a sweat).
    Hence the invention of the torque-wrench.


    ************************************************** *************
    Carolyn F. Small, PhD, PEng
    Professor, (613)545-2581
    Department of Mechanical Engineering FAX 545-6489
    Queen's University
    Kingston, Ontario, Canada
    K7L 3N6
    ************************************************** *************
    From: "Karl Kraus" Reply-To:

    As you might guess, there is quite a bit of variability not only between
    surgeons, but with different screw driver handles. We conducted a study of
    ten surgeons using a screw driver type wrench and an open ended wrench with
    a 15cm handle. The mean with the screw driver was 4.4 Nm and 7.8 with the
    open ended wrench. (Kraus et al, Vet surg., 1998)

    Maximum torque will depend on a lot of factors: Handle diameter,
    orientation, arm posture, surface roughness etc. A better question is how
    can this device be designed so that the surgeon can tighten the screw with
    only a small amount of force?
    Stephen Pheasant discussed the issue of screwdriver design and torque in
    his book:
    Bodyspace: Anthropometry, Ergonomics and the Design of Work, 2nd Edition,
    Taylor & Francis, London, 1996.
    He also referred to two earlier papers:
    Pheasant ST and O'Neill D (1975) "Performance in gripping and turning",
    Applied Ergonomics, 6, 205-208.
    Pheasant ST and Scriven JG (1983) "Sex differences in strength - some
    implications for the design of hand tools". Proceedings of the Ergonomics
    Society Conference 1983, ed. K Coombes, Taylor & Francis, London, pp 9-13.
    Ergonomics and Work Psychology Section
    Health and Safety Laboratory, Broad Lane, Sheffield, S3 7HQ, UK Tel +44 114
    289 2594; Fax +44 114 289 2526 HSE home page: -

    From: "Eric Powell"

    Why not try to find out for yourself? You could weld a nut socket to the
    end of a screwdriver. Then attach this to a torque wrench used for car
    maintenance, hold the wrench in a vice, and get your volunteers to try and
    turn the torque wrench.


    Dr Eric Powell
    Research Bioengineer
    Rehabilitation Research
    Phase 2
    Hope Hospital
    Eccles Old Road
    Salford M6 8HD
    United Kingdom
    telephone: (44) 0161 787 1128
    From: "Kazakia, Galateia"

    Dr. Viceconti,
    I have recently been addressing this question myself. It seems that some of
    the best data comes not from the orthopaedic field, but from US Government
    sponsored studies meant to aid in the design of air and space craft
    A report available from the Center for Aerospace Information of the
    National Aeronautics and Space Administration (NASA) entitled
    "Anthropometric Source Book" (NASA RP-1024) is a compilation of a large
    amount of anthropometric data aimed to meet the needs of engineers
    designing clothing, equipment, and workspaces for the NASA Space Shuttle
    Program. This information is, of course, very useful for engineers in a
    variety of fields. Volume I contains a chapter entitled "Human Muscular
    Strength". It contains much strength information including data on volar
    flexion/dorsal extension and supination/pronation strength for both men and
    women. The most relevant references from this chapter seem to be:

    1. Asmussen E, and Heeboll-Nielsen K, 1961. "Isometric Muscle Strength of
    Adult Men and Women, " Communications from the Testing and Observation
    Institute of the Danish National Association for Infantile Paralysis, 11:

    2. Backlund L, and Nordgren L, 1968. "A New Method for Testing Isometric
    Muscle Strength Under Standardized Conditions," Scandinavian J. of Clinical
    and Laboratory Investigation, 21(1): 33-41.

    3. Lauback LL, 1976. "Comparative Muscular Strength of Men and Women: A
    Review of the Literature," Aviation, Space, and Environmental Medicine,
    47(5): 534-542.

    4. Lauback LL, 1976. Muscular Strength of Women and Men: A Comparative
    Study. AMRL-TR-75-32, Aerospace Medical Research Laboratories,
    Wright-Patterson Air Force Base, Ohio.

    This report (NASA RP-1024) and others can be found (and ordered?) on the
    following page:

    I hope this is helpful!

    Galateia Kazakia
    Design Engineer
    The Hospital for Special Surgery

    phone: 212.606.1434
    fax: 212.794.4020

    From: "w.p. mossel"

    Dear MARCO
    The question is wrong. Because it depends on the diameter of the grip of
    the srewdriver. I am not a surgeon and I don't know with what kind of
    screwdrivers surgeons work. For instance when the handle has a T-form the
    torque can be larger than with a handle with a small cilinder form . I am
    now at home and not in the university. I thought I had some values about
    the torque of human hands. On monday I'll be in the university and will
    mail you what I have about torque.
    "All spelling errors due to line noise"
    Kind regards, Vriendelijke groet, Grusze Wim Mossel

    Phone: +31 15 278 35 64, Fax: +31 15 278 71 79 Address : Jaffalaan 9
    2628 BX Delft
    The NetherlandsDate: Fri, 01 May 1998 11:55:36 -0400
    From: Kevin Bender

    Try the following references:

    Mital & Channaveeraiah. "Peak volitional torques for wrenches and
    (1988), 41-64.

    Shih & Wang. "Hand/tool interface effects on human torque capacity."

    Kevin Bender, Ergonomist
    Ontario Ministry of Labour
    2nd floor West Building phone: (416) 235-5322
    1201 Wilson Ave fax: (416) 235-5080
    Downsview, Ontario M3M 1J8
    From: Enzerink

    Take a look at the Human Factors Handbook. I do not have the data
    immediately available, but I know it is in there. This data is mostly from
    adult males in the US military, so values need to be lowered a bit for the
    average population. The book also references torque values relative to
    driver handle sizes, orientation, etc.
    Good Luck. If you cannot find it, let me know and I'll look up the numbers
    you need.

    Robert Enzerink
    Director, R&D
    DePuy OrthoTech
    From: Dhendry
    The torque depends on the structure of the tool. The maximum torque is
    infinite (as for Atlas)
    From: Dhendry
    The maximum practical torque is exerted with a T-shaped handle. This torque
    is about 60 ft-lbs for a normal man (you can convert to Nm)
    From: Margarita Vergara Monedero

    A good reference is:
    'Human force exertion in user-product interaction. Backgrounds for design'
    B.J. Daams, 1994, Delf University Press, ISBN 90-6275-995-5
    __________________________________________________ __________

    Margarita Vergara Monedero Tfn. 34-964 34 56 80 Ext. 4757 Departamento
    de Tecnologia
    Fax 34-964 34 56 46 Universitat Jaume I
    e-mail: E-12071 Castello SPAIN
    From: (mossel, w.p.)

    Dear Marco,
    I found the following jounal articles in my files:

    AU[ Pheasant, S., O'Neill, D.]
    TI[ Performance in gripping and turning- A study in hand/handle
    effectiveness] JN[ Applied Ergonomics]
    YR[ 1975]
    VO[ 6]
    IS[ 4]
    PG[ 205-208]

    AU[ Nagashima, K., Konz, S.]
    TI[ Jar lids: effect of diameter, gripping materials and knurling] PU[
    Human Factors Society]
    PL[ Dayton, Ohio]
    YR[ 1986]
    PG[ 672-674]

    AU[ Bordett, Harvey M.; Koppa, Rodger J.; Congelton, Jerome J.] TI[ Torque
    required from elderly females to operate faucet handles of various shapes]
    JN[ Human factors]
    YR[ 1988]
    VO[ 30]
    IS[ 3]
    PG[ 339-346]

    I think the first of the late Stephen Pheasant gives the best answer to
    your problem.
    He has also written two books:
    Ergonomics, work and health, MacMillan, Basinstoke, 1991, ISBN
    0-333-48998-5 Bodyspace,...Taylor & Francis, London, 1986, ISBN
    Probably you can find something about your problem in it.
    And there are values for the torque in:
    Daams, B.J., Human Force exertion in user-product interaction, Delft
    University Press, 1994, ISBN 90-6275-995-5

    Hope this helps,

    "All spelling errors due to line noise"
    Kind regards, Vriendelijke groet, Grusze Wim Mossel

    Phone: +31 15 278 35 64, Fax: +31 15 278 71 79 Address : Jaffalaan 9
    2628 BX Delft
    The Netherlands
    From: "Paolo de Leva - Sport Biomechanics, Rome, IT"

    non so se ti può servire, ma mi viene in mente che, come esperienza
    insegna, il momento massimo è inferiore al massimo teoricamente
    "possibile", perchè di solito la spinta esercitata dalla mano verso la vite
    risulta insufficiente... e il cacciavite si sfila dalla testa della vite.
    Questo non succede con una chiave a brugola (più consigliabile).


    Laboratorio di Tecnologia dei Materiali tel. 39-51-6366865
    Istituti Ortopedici Rizzoli fax. 39-51-6366863
    via di barbiano 1/10, 40136 - Bologna, Italy

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