How an Impact Driver Work? – Mechanism, Usage, Troubleshoot

An impact driver is a great tool for driving screws into wood and through low-thickness metal plates. Impact driver produces rotational hammering force that can be applied on the screws as it can turns. Sometimes you can use an impact driver as a drill. So let’s see in detail about impact driver mechanism, usage, and troubleshooting.

The impact driver works as a rotational hammering action, and it can apply more torque to the driving bit. It is used to drive screws, nuts, and bolts. Hex shank is used to hold the tool instead of the chuck. Applied torque can be increased according to the driving material and driving bit.

Using an impact driver will not force the hand. It can be used easily by hand, and also, there is a simple mechanism that can repair or maintenance well. So let’s keep on more detail about the impact driver and how it works?

12 Types Drill Bit for Wood
12 Types Drill Bit for Wood

Impact Driver Mechanism

Impact Driver Mechanism
The impact driver produces the rotational hammering force. It is like applying a hammering force to the nut that is to be loosened. It is more complicated than a regular drill. You can’t use the regular drills as an impact driver with using an impact mechanism. But you can use an impact driver as a regular drill. So let me explain step by step.

There are 03 main parts to the impact driver. Those are Motor, Hammer part, and Anvil. Each part has a specified task.

Impact-driver-main-parts
Main Parts of impact Driver Source
Impact Driver Inside Mechanism Source

Motor – Produce the rotational motion to the impact driver.
Hammer part – It acts as a hammerhead. This rotates with two teeth. When the teeth head has touched the anvil, it starts to move. Because of the teeth angle, the hammerhead moves backward and is ready for the next turn. There is a spring, and it can push the hammerhead forward when the teeth are missed.

Anvil – Anvil is the tool head. It s the driver mounting unit. When the anvil is rotationally forced, it is started to moving with the driver bit and screw. There is no hammering force along the drive bit. Therefore using a hammer drill is impossible.

How Impact Driver Mechanism Helps to Drive Screws?


When we need to drive the screw by hand, we need to push the screws and turn the screwdriver. We push to hold the rotational force from hand. Else it will slip. But actually, pushing force is less than rotational force. But when we use the hand, we are not able to do so.

But using an impact driver is a straightforward task. Only we need to hold the tool. The impact mechanism will produce many rotational forces. A number of hitting the hammerhead on the anvil per minute is called impact per minute. It is about 2000 for speed gear 1 and gear 2 it is more than 4000. It depends on the tool.

The impact rate will depend on the speed of the motor (RPM). More impact rate is greater than less impact rate. When you are going to buy, you should select a high impact rate impact driver.

Impact Mechanism and Torque

Due to the impact mechanism, torque is produced. Normally torque is measured with Nm, in-lbs, or ft-lbs. You can follow the bellow to convert each other.

  • 1 ft-lb = 1.3558 Nm
  • 1 ft-lb = 12 in-lb
  • 1 in-lb = 0.112 Nm

House using impact drivers are mostly measured with in-lbs, and high capacity drivers are used ft-lbs. When you use a high torque tool, you can work in a wide area.

Types of Torque

Tighten torque and Breakaway Torque
Tighten torque is the torque for tight the screw or nut. Breakaway torque is used to lose the nut or screw. Normally loose a screw will need more force than tighten it. So always tighten torque is always less than Breakaway torque. Breakaway torque is the maximum torque that a tool can produce.

Chuck And Drive Bits of Impact Driver

Driving tools are mount to the chuck. Chuck is named a hex shank. More driving tools are with hexagonal cross-sections because driving produces more torque. If there is a circular section, the driving bit can be subjected to torsion.
When the hexagonal section resists more than a circular cross-section, due to this, these tools are mounted to the hex shank.

There is no key mechanism, and the magnet power in the tool and the shank will hold it. There are drive bits that can be damaged easily. So when you buy that, you should select high abrasion to resist tools. The strength of the drive bit tool depends on the material and the structure of the manufacture. Milwaukee Shockwave (0.66$) can resist 157Nm torque.

Best Tool Usage
You must use more torque driver bits than impact driver maximum torque. If the impact driver activated its maximum torque, the driver bit would be broken.

Driver BitTorque (Nm)
Milwaukee Shockwave $0.66157
Wiha $1.20157
Irwin $0.52149
Makita gold $0.66149
Hercules $0.45148
Bosch $0.53146
Bauer $0.43144
Craftsman $0.50143
Dewalt $0.53140
Warrior $0.1993
Types of Driver Bits and Maximum Torques Source: Project Farm

According to this, you can have an idea for investing money for the drive bits.

How to Repair an Impact Driver?

Impact Driver Repair Steps.

  • Remove the battery or power cord
    Before remove the scres of the outer case disconnect form the power source for the safety
  • Remove the housing by removing the tight screws and stickers.
    Screws are tighten and fixed the case. Some time there are stickers. So you need to remove them
  • Then remove the trigger with its light connections.
    Front lights connection should be removed with its socket and remove the treger.
  • Lift gearbox and motor.
    Take out the gearbot and motor with safely.
  • Remove the armature from the gearbox.
    You can remove the armature and gearbox now. Seperate the electical parts and mechnaisl parts.
  • Remove LED lights and its connections.
    Beofre seperate the fornt hammering part you should remove the front lights.
  • Remove the impact mechanism part from the nose cone. Use a screwdriver.
    By using screw driver loose the supports of the hammer part
  • Separate the inside anvil and hammer
    After having the hammer part you can seperate the anvil, spring and hammer head.
  • Apply grease inside the hammerhead and springs.
    It there is essetial repairs do them. Else apply the grease.
  • Identify the problems if there is.
    Check the problem that you had and fix it. If a part is damaged replace that.
  • Then rewind the process for fix again.
    Now you can rewind the steps for assembling
  • Reconnect the wires and establish the brushes.
    If it is a brushed motor connect it with the wires
  • After fixed tighten the screws.
    Then tighten the screws well and test it.

Why My Impact Driver is not Turn On?

Reasons for the Impact Driver Do not Turn on.

  • Brushes are fully scratching
  • Inside electric leaking
  • Battery can be dead
  • The trigger can be not working properly
  • The trigger assembly is disconnected
  • Using overheated battery
  • using overcooled battery

Check the difference between brushed vs. brushless

Why my Impact Driver Torque Has Reduced?

Reason for the Torque Reduce in Impact Drivers

  • Battery power reduce
  • The problem in the brushes
  • Use low capacity batteries
  • In short circuit
  • Trigger has clogged
  • wires are loose

Why Impact Driver Trigger is not Working?

Reason for the trigger problems

  • The battery is dead
  • Brushes are scratches
  • The forward/reverse switch is not fully engaged to one side
  • Inner wires are loosen
  • Internal lock is inoperative

Solution for the driver overheating.



Tom Mackenzy

I am Tom, I am really interested in DIY projects. I have my own workshop and I spend my free time with so many projects. So I would like to share my experience with you regarding power tools, woodworking, metalworking, etc.

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