What Metric Fastener Drive Type Should You Be Using?

Like most aspects of construction and manufacturing, choosing the proper tool for the job goes a long way toward determining the project’s success. Selecting a metric fastener’s drive recess (the slot or hole into which the driving tool is inserted) is no different. Drive recesses, from Phillips head screws to more unusual shapes and specialized uses all have advantages and disadvantages. Take a look at some of the drive types Mr. Metric offers to learn about which style is right for your job.

Ensure Proper Tightening & Removal of Metric Fasteners With the Right Drive Type

metric screw slottedSlotted – The first and still one of the most common varieties, slotted metric screws are inexpensive and come in virtually any head shape desired. They are also the easiest to torque when using a screwdriver to remove corroded or frozen fasteners, so they are often used when field installation and/or removal is necessary. However, they are unsuited for automated driving because the single slot allows the bit too much tolerance, and slippage and off-center engagement can occur.

metric screw phillipsPhillips – Again, quite common and handy for many everyday uses, Phillips screws are designed so the driver slips out of the slot (cams out) when the fastener is tight, preventing damage to the clamped material due to excessive torque. Self-tapping metric Phillips screws are often used in rapid manufacturing applications because the bit easily engages the +-shaped threads.

metric screw hexHex Key (Allen) – The greatest advantage in using metric screws with regular hexagonal recesses is that the Allen wrenches used to drive them require much less tool clearance than traditional driver-turned screws, making them popular in furniture making and electronics. The Allen wrenches’ shape also lends itself to efficient high-torque transfer.

metric screw six lobeSix Lobe (Torx) – Favored by the electronics industry, the six-pointed star-shaped hole creates additional contact points with the driver. The expanded contact area prevents cam out and bit wear and permits the user to transfer torque with less effort than is required with other drivers, even with an angled driver. These screws have gained wide acceptance with appliance and automobile manufacturers, and are making their way into other applications as more sizes become widely available and producers and maintenance companies obtain the required bits.

metric screw duel driveDual Drive – Combining a recess with a hexagonal head, dual drive metric fasteners can be driven with either the tool that matches the recess or with a wrench (open-ended or ratchet). The wrench-accessible head comes into play primarily on applications where the large and heavy-duty screws can be power driven, while the recess can be used to adjust, maintain, or tighten the fasteners, so they are common in construction, automotive, and other industrial applications.

metric screw tamper resistantTamper Resistant –Torx, Allen and a few other fastener styles are made tamper resistant by adding a pin to the center of the recess, preventing the standard Torx or Allen bit from engaging. Restricting access to the corresponding bit (that is, one with a matching hole in the tip) prevents unauthorized removal or tampering.

To ensure proper tightening and removal and to guard against damaging the screw head, always use not only a fastener’s corresponding bit style, but also the precise size. While slotted and Phillips drivers work on both metric and English screws, use only metric hex bits and sockets when working with metric hex key and dual drive fasteners, respectively.

Still need help selecting the right drive type for your metric fastener? Contact us or call us 1-866-501-9504 to speak with one our knowledgeable representatives.


About the author

Mr. Metric is the spokesperson for www.mrmetric.com, an online store for metric fasteners. Get $7.50 flat shipping with no minimum orders, plus advice and best practices for using metric fasteners in any application.

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