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Cam-Out – What Is It?
How Can It Be Avoided?


You might not be familiar with the specific expression ‘cam-out’ just yet, but we can almost guarantee that you’ve experienced it in practice.

It happens when the screwdriver, or the screwdriver bit, you’re using slips out of the screw’s head while you’re trying to tighten or loosen the screw.

Cam-out is pretty common among amateur DIYers and professionals alike. At best, it’s a slight annoyance that’s usually coupled with a bit of swearing, although, at worst, it can lead to stripped screws which can be a real headache to remove.

Thankfully, it’s pretty easy to avoid cam-out altogether, and we’ll be showing you three quick and easy steps to do precisely that.

Let’s get stuck in…


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What is Cam-Out?

As mentioned, cam-out is the term given to when a screwdriver bit slips out of a screw’s head while tightening or loosening the screw.

It happens when the torque (turning power) applied to the screwdriver causes the tip to be pushed upwards and out of the screw’s head while turning.

Besides being annoying and making you feel like an amateur, the slipping motion can cause damage to the screw head and whatever screw bit or screwdriver you are using.

Cam-out tends to get progressively worse the more you ‘persist’ and continue to try and insert or remove the same slipping screw with the same bit type.

As damage continues to occur to the screw’s head or the screwdriver bit, it becomes harder and harder to either insert or remove the screw each time, and you run the risk of stripping the screw head altogether.

If you’ve ever experienced a stripped screw, you’ll understand just how difficult they can be to remove and why you’d want to avoid this situation by preventing cam-out in the first place.


What Causes Cam-Out?

Several factors can lead to the screwdriver’s bit slipping and camming out.

These include:

  • Using Softer Screws or Damaged Screwdriver Bits
  • Generally, softer screws, for example, brass, will be more susceptible to cam-out, so make sure you’re selecting the best screw material depending on the application.

    It’s a good idea to replace any damaged screwdriver bits before use, too. Any defects or damage could prevent a flush fit with the screw and increase the risk of slippage, which could damage the screw’s head.

  • Using the Wrong Type of Screw
  • Phillips drive screws are synonymous with cam-out, particularly if you’re using the wrong sized bit relative to the screw’s drive size, and if you’re working with larger fixings and more robust materials that require greater torque to turn the screw.

    There are better drive types available for minimizing slippage, as covered later in the article.

  • Not Applying Sufficient Downward Force
  • Without enough force pushing through the bit and into the screw, the tendency is for the bit to pop up and out while turning (especially when using Phillips drive screws).

    When this occurs, it can lead to damage of the screwdriver bit, the screw’s drive, or both, and increase the likelihood of slippage.

  • Using the Tool out of Alignment
  • With the screwdriver bit tilted off-axis to the screw’s drive, there won’t be a flush bit between the bit and the screw. The bit will, therefore, be in contact with less surface area in the screw’s head, increasing the risk of cam-out, especially in situations where more turning power is applied.

How to Avoid Cam-Out – 3 Simple Steps

Follow these three steps, and you should minimize most, if not all, of the potential for cam-out when inserting or removing screws:
1
Use the Correct Tool
Perhaps the most crucial step of all in avoiding cam-out is to use the correct tool for the job.

Now, we’re not talking about choosing between a handheld screwdriver and an electric drill driver here, but rather, choosing the correct size bit relative to whichever screw you’re using.

Simply put, if the screwdriver bit moves around and does not sit flush in the screw’s head (as shown below), the bit and head size are mismatched, and so you’re at greater risk of experiencing cam-out.

an image showing the correct and incorrect fit of a screwdriver bit in a screw. A poor fit could cause you to cam out screw

A #0 or #1 sized Phillips wood screw, for example, is best suited to a #0-sized driver, whereas a #1 sized driver is best suited to Phillips wood screws between #2 and #4.

Using a bit size other than that recommended by the manufacturer of whichever screw you’re using will increase the likelihood of slippage.

Finally on the subject of screwdriver bits, if avoiding cam-out is essential, it’s probably a good idea to replace your screwdriver bit if it’s showing any signs of wear and tear. Any damage could prevent a flush fit and result in movement between the bit and the screw’s head causing slippage.

2
Use the Correct Type of Screw
It’s worth remembering that Phillips drive screws are notoriously prone to cam-out. You can minimize the risk somewhat, of course, by correctly matching the drive and bit size as managed above.

A better option, however, could be to choose a different drive type altogether, particularly in tougher situations where you’re using larger fixings or where you’re screwing into tougher materials.

  • an image of a Phillips drive screw head Phillips Drive
  • an image of a star Torx drive screw head Star Drive
  • an image of a square Robertson drive screw head Square Drive
  • an image of a hexagonal Allen drive screw head Hexagonal Drive

Drives like star (Torx), square (Robertson), or hexagonal (Allen) shown above are particularly favourable in these situations. These drive types increase the surface area between the screwdriver bit and the screw head, giving a much better grip which minimizes the risk of slippage and cam-out.

Not only that, but these drive types rely on a much more parallel connection between the bit and the screw (unlike a traditional Phillips drive screw profile when viewed side-on, which allows the screwdriver to rise up and out of the screw). The flatter face between the screwdriver bit and the drive’s walls largely prevent the bit pushing up and out, transmitting the turning power or torque fully into the screw instead.

It’s also worth paying attention to the material of the screw you’re using, too.

Brass screws, for example, are much softer than stainless steel screws, and so are more prone to damage around the drive that could lead to cam-out in the future. Generally, the stronger and more robust the screw, the less likelihood there is of slippage.

3
Maintain Balance and Alignment
Finally, it’s essential to keep the screwdriver bit perfectly aligned with the axis of the screw as shown in the image below. Any tilting will place the bit off-axis, preventing a flush fit between the screwdriver bit and the screw’s head.

In these situations, the bit will be in contact with less of the screw head’s surface area, increasing the risk of slippage, particularly in torquier applications like driving in larger screws or working with more robust materials.

an image showing the correct alignment of a screwdriver bit relative to the screw to minimize the risk of camout

It’s crucial to maintain enough ‘pushing’ force behind the tool, too, mainly when working with screws with a Phillips drive.

Without enough force pushing into the bit, the natural tendency is for it to pop up and out, leading to cam-out and damage of the bit, screw head, or both. There’s no need to get too scientific here (as you’ll feel when the bit is starting to slip and when you need to apply more force), but the folks at NBK state that about 70% of pushing force versus 30% of turning force is a favorable mix to prevent slippage.


Final Remarks

As you can see, there’s absolutely no reason to put up with cam-out, no matter how common it may be.

From using the right bit size and the correct bit type to maintaining alignment between the tool and screw, we hope these tips help you avoid the headache of stripped screws altogether going forward.

If you still have any questions or queries that we haven’t answered above, feel free to leave a comment below, and we’ll do our best to get back to you as soon as possible.

Thanks, and good luck!


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