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The technology behind driving the fasteners into their slots has drastically improved right from the age of screw drivers to cordless drills. In today’s modern era, automatic machines have made it easier to carry out fastening operations without dealing with much disorientation. However, driving the screws into their holes with millimeter precision requires practice and skill of the operator. Overdriving the fasteners can reduce the pull-out strength and shear capacity by 5-22%, depending upon the extent to which the nail is overdriven.

The permissible shear capacity of walls is dependent upon the fastener size, volume, type and the extent to which it is penetrated into the slot. In order to counter the effect of overdriving your fasteners, additional fasteners may be used to balance the recommended space requirement. However, this kind of a situation can be avoided by few simple hacks.
never overdrive fastener so shear capacity is maintained

Adjusting the driver’s slip clutch

Located at the rear end of the chuck, the slip clutch indicates the torque power that is transferred to the head of the fastener. You need to be trained at using the clutch in order to bore the fastener to the required depth, without falling prey to overdriven or under-driven situation. The slip cutch setting is such that if surpassed by the force required to drive in the fasteners, the clutch will slip and the motor will continue to drive, without the chuck turning. You can only derive at the ideal number by experimenting with different torque setting. This setting depends on a lot of factors, mainly, the type of fastener, its dimension and the hardness of the materials being fastened together.  For soft wood materials, generally little torque is required, but you need to crank up the clutch for hardwood and metals.


Using self-centering bits

In spite of a sturdy hand and eye combination, it sometimes becomes difficult to drill a perfect slot for fasteners with millimeter accuracy. If the hole gets misaligned from the center, you’ll probably end up overdriving the fastener in the wrong direction. In order to get that perfectly centered position of the Monel 500 screws, consider using a self centering bit to mount the parts more precisely, without compromising the shear-capacity. This is especially useful for inserting longer threads.

Drilling pilot holes

Pilot holes prevent the fasteners from breaking in half or being overdriven, which is quite imperative when driving brass screws inside the hole. It is basically a hole of low diameter bored at the base of the board. The main objective is to provide a pathway for the fastener to enter the slot without ripping it apart, and hence minimizing the chances of shear-capacity reduction.

Practicing to master the expertise

Overdriving the fasteners is a common error that happens more often than not, and especially if you are new to driving the screws, you have a tough job at hand.  Getting used to this skill takes practice just like archery.  You are only going to learn with several repetitions till the time your hands fit the purpose.

About the Author

Larry Melone
By Larry Melone

Started my career in the fastener world in 1969 at, Parker Kalon Corp. a NJ based screw manufacturer located in Clifton, NJ working in inventory control, scheduling secondary production and concluding there in purchasing. In 1971 I accepted a sales position at Star Stainless Screw Co., Totowa, NJ working in inside sales and later as an outside salesman, having a successful career at Star I had the desire with a friend to start our own fastener distribution company in 1980 named: Divspec, Kenilworth, NJ. This was a successful adventure but ended in 1985 with me starting Melfast in August 1985 and have stayed competitive and successful to date. Melfast serves the OEM market with approximately 400 accounts nationally.

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