1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I Equation to calculate torque to hold drill while drilling?

  1. Mar 9, 2017 #1
    i need to know how to calculate the torque needed to apply through my hand to hold a certain hand drill in place while drilling in concrete wall so that the hand drill willl rotate the bit instead of my hand.
  2. jcsd
  3. Mar 9, 2017 #2


    User Avatar
    Science Advisor
    Homework Helper
    2017 Award

    I suppose you do. What are the parameters and relationships you have at your disposal to do this calculation ? Wouldn't it be easier to determine what you want to know experimentally ?
  4. Mar 10, 2017 #3
    i just need to know the general equation for a torque i need to apply, i think if we assume that the force from the concrete wall is 10 newtons i would have to apply more than 10 newtons right?
    it's the difference in forces that gives this relation right?
    if i put 9 newtons from my hand and 10 newtons is coming out of the wall then my drill and hand will rotate with force of -1 newtons which is the opposite direction i think??
    would appreciate your help
  5. Mar 10, 2017 #4
    You can estimate it using nomimal power of the drill as the maximum torque you need to hold the machine. Remember P= T x w the speed i suppose is known.
  6. Mar 10, 2017 #5


    User Avatar
    Science Advisor
    Gold Member

    In a drilling operation there is :

    (1) A thrust force along the axis of the drill . This is what causes the cutting edges to dig into the material being drilled and so enable the cutting action .

    (2) A torque about the axis of the drill . This is what causes the cutting edges to rotate about the drill axis and actually do the cutting .

    The thrust force and the torque are interrelated .
  7. Mar 10, 2017 #6


    User Avatar
    Science Advisor

    A torque is more than just a force. It involves a force and an offset between the point of application of the force and the axis of rotation. The longer the handle on a wrench, the less force you need to budge a stuck nut. Accordingly, the appropriate units for a torque involve a force times a distance. For instance, a Newton-meter or a pound-foot.

    The torque with which the wall can resist a drill bit will depend on at least two things:

    1. How hard are you leaning on the bit? The harder you push, the more friction between the bit and the concrete in the hole.
    2. How big is the diameter of the bit? The bigger the bit, the more torque that frictional force can produce.

    Of course, all of this is limited by how much torque the drill can produce. Newton's third law applies for torque as well as for force: The torque the drill applies to the wall is equal and opposite to the torque the wall applies on the drill. If the drill can only produce 10 Newton meters of torque then the wall will only provide 10 Newton meters of resistance. If that's not enough to rotate the bit then the bit will be stuck.

    If you manage to provide 9 Newton meters of torque from hand to drill and there is 10 Newton meters of torque between wall and drill, then yes, that's 1 Newton meter of excess torque. This will result in angular acceleration -- the drill will twist out of your hands.

    If you can provide 11 Newton meters of torque while the drill can only produce 10 Newton meters of torque then you will only have to provide 10 Newton meters of torque and the drill will not twist out of your hand.

    Some drills come equipped with threaded holes into which you can screw auxiliary handles so that instead of holding the drill in a one-handed pistol grip, you can hold it with two hands like a lug wrench. In addition to allowing you to use two hands, that puts your hands farther from the axis of rotation so that you can get more "leverage" -- more torque for the same applied force.

    None of this helps much to produce an actual calculation. It's easier to put drill to wall, and see whether you can hold it or not.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted