Date Published:Oct. 12. 2017

Vol. 8 Why a Cross recess gets broken: What is "cam-out"?

Hey there! Nedzigon's back!
Breakage of cross recess, making it impossible to remove the screw, is a familiar phenomenon to many of us. One of its causes is "cam-out". Say you have a factory where screws are automatically tightened; sometimes cam-out causes a large amount of tightening defects.
Today, I will explain the principles of "cam-out" and how they can be resolved.

What is "cam-out"?

"Cam-out" is a phenomenon where the tip of a tool such as a screwdriver or bit disengages from the screw while turning it. The cross recess is tapered towards the center (the tip is narrowed), right? The tip of the tool is also tapered to fit the cross recess, so when you turn it, force is applied laterally; the force escapes along the taper diagonally and causes the tool to disengage. When this happens, problems such as breakage of cross recess, groove collapsing, and tool tip crushing occur.

How can we prevent "cam-out" from happening?

The balance between 'turning' and 'pushing' is important

As I mentioned, the cross recess shape allows the tightening tool to disengage easily.
To prevent this, we have to push the tool in while turning it.
Generally speaking, the pushing force should be 70% while the turning force is 30%.

Keeping the "axis" steady is important

It is also important that the screwdriver or bit is straight with respect to the screw.
If not, the rotating axis will shift, which prevents the turning force and pushing force from transferring well, causing the tool to disengage and resulting in cam-out.

Pay attention to the size of the tool and the screw cross recess

If the sizes of the screwdriver or bit and screw do not match, cam-out is more likely to occur.
If the tip of the tool does not fit perfectly into the cross recess grooves, the tool is more likely to disengage.
However, even with a screwdriver that matches the screw, extended use causes the tip to wear out and leads to cam-out.

Screws that reduce the risk of cam-out

Compared with the cross recess, cam-out does not occur as easily in hexagonal or hexalobular sockets. Moreover, the hexalobular socket exhibits higher transmission efficiency of tightening torque compared to hex sockets.

>>Learn more about the characteristics of hexalobular sockets

Also, screws with QuaStix* cross recess can prevent cam-out when used with dedicated bits.

>>Learn more about QuaStix

*:QuaStix is a registered trademark of OSG System Products.

If cam-out occurs and cross-recessed sockets are crushed...

No matter how careful you are, I think that cam-out will still sometimes occur, and cross-recessed sockets will be crushed or stripped. But that's OK. Because there are tools for removing screws when they cannot be removed with normal tools.

Stripped Screw Removal Bits SKEIB-PH

That's it for today.

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