Pilot hole

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Drilling pilot holes to hammer nails Drilling Pilot Holes.jpg
Drilling pilot holes to hammer nails

In construction, a pilot hole is a small hole drilled into a piece of construction material. Its purpose may be:

Contents

  1. to guide a larger drill to the appropriate location and ease the job of the larger drill
  2. allow for the insertion of another hole-making tool, such as a knockout punch, that will produce the final-sized hole, or
  3. locate, guide, and provide clearance for a self-threading screw in wood or plastic to prevent damaging the material or breaking the screw.

Pilot for large holes

A pilot hole may be drilled the full extent of the final hole, or may only be a portion of the final depth. The pilot drill may be a standard twist drill, another type of drill bit appropriate for the material, or, when the primary purpose is precisely locating a hole, may be made with a short, stiff center drill.

The pilot hole also reduces the power needed to turn a large drill bit, and reduces the large bit breakage risk. For twist drill bits, the pilot size is usually selected so that the chisel point of the larger drill does not need to remove any material, which reduces the chance of splitting the web of the bit. A pilot thus sized also prevents a larger drill bit from slipping on the material and guides the larger bit effectively. Very large holes may be stepped by drilling successively larger pilot holes before the final size drill is used. [1]

On harder materials, such as most metals and many plastics, and sometimes on softer materials like wood, a center punch is used before drilling the pilot hole to ensure that the smaller pilot drill bit does not slip and that it starts at the correct location.

Pilot holes for screws

Pilot holes may be used when driving a screw, typically in wood, concrete, or plastic where the screw cuts its own threads.

When a screw is driven into a material without a pilot hole, it can act as a wedge, generating outward pressure which can cause many materials to split. By drilling a small pilot hole into the material, into which a screw is then driven, less wedging takes place, thereby reducing the likelihood of the material being split. [2]

When a screw is driven without a pilot hole, or with too small a pilot hole, the core of the screw may bind and lead to the screw being broken. The appropriate pilot hole will prevent binding while providing sufficient friction to keep the screw from loosening. For common wood screws, the pilot providing clearance for the core of the screw may be followed by a larger bit to shallower depth to provide clearance for the larger, unthreaded shank of the screw. For standard wood screws, special pilot drill bits are manufactured to produce the correct hole profile in a single operation, rather than needing several different drill bit sizes and depths. [3]

Screws driven into concrete must have the appropriate size pilot hole, or they will either break on insertion, strip the hole, or not provide the rated holding force. [4]

A hole drilled for tapping machine screws or bolt threads in metal or plastic may also be referred to as a pilot hole.

Related Research Articles

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<span class="mw-page-title-main">Tap and die</span> Tools to create screw threads

Taps and dies are tools used to create screw threads, which is called threading. Many are cutting tools; others are forming tools. A tap is used to cut or form the female portion of the mating pair. A die is used to cut or form the male portion of the mating pair. The process of cutting or forming threads using a tap is called tapping, whereas the process using a die is called threading.

<span class="mw-page-title-main">Drill bit</span> Type of cutting tool

Drill bits are cutting tools used in a drill to remove material to create holes, almost always of circular cross-section. Drill bits come in many sizes and shapes and can create different kinds of holes in many different materials. In order to create holes drill bits are usually attached to a drill, which powers them to cut through the workpiece, typically by rotation. The drill will grasp the upper end of a bit called the shank in the chuck.

A reamer is a type of rotary cutting tool used in metalworking. Precision reamers are designed to enlarge the size of a previously formed hole by a small amount but with a high degree of accuracy to leave smooth sides. There are also non-precision reamers which are used for more basic enlargement of holes or for removing burrs. The process of enlarging the hole is called reaming. There are many different types of reamer and they may be designed for use as a hand tool or in a machine tool, such as a milling machine or drill press.

<span class="mw-page-title-main">Self-tapping screw</span> Type of screw

A self-tapping screw is a screw that can tap its own hole as it is driven into the material. More narrowly, self-tapping is used only to describe a specific type of thread-cutting screw intended to produce a thread in relatively soft material or sheet materials, excluding wood screws. Other specific types of self-tapping screw include self-drilling screws and thread rolling screws.

<span class="mw-page-title-main">Mandrel</span> Gently tapered cylinder against which material can be forged or shaped

A mandrel, mandril, or arbor is a tapered tool against which material can be forged, pressed, stretched or shaped, or a flanged or tapered or threaded bar that grips a workpiece to be machined in a lathe. A flanged mandrel is a parallel bar of a specific diameter with an integral flange towards one end, and threaded at the opposite end. Work is gripped between the flange and a nut on the thread. A tapered mandrel has a taper of approximately 0.005 inches per foot and is designed to hold work by being driven into an accurate hole on the work, gripping the work by friction. A threaded mandrel may have a male or female thread, and work which has an opposing thread is screwed onto the mandrel.

<span class="mw-page-title-main">Countersink</span> To bevel the rim of a hole, so a fastener can be inserted flush with the surface

A countersink is a conical hole cut into a manufactured object, or the cutter used to cut such a hole. A common use is to allow the head of a countersunk bolt, screw or rivet, when placed in the hole, to sit flush with or below the surface of the surrounding material. A countersink may also be used to remove the burr left from a drilling or tapping operation thereby improving the finish of the product and removing any hazardous sharp edges.

<span class="mw-page-title-main">Chuck (engineering)</span> Clamp used to hold an object with radial symmetry, especially a cylinder

A chuck is a specialized type of clamp used to hold an object with radial symmetry, especially a cylinder. In a drill, a mill and a transmission, a chuck holds the rotating tool; in a lathe, it holds the rotating workpiece.

<span class="mw-page-title-main">Turning</span> Machining process

Turning is a machining process in which a cutting tool, typically a non-rotary tool bit, describes a helix toolpath by moving more or less linearly while the workpiece rotates.

<span class="mw-page-title-main">Butt joint</span> Techniques to join two pieces of wood together

A butt joint is a technique in which two pieces of material are joined by simply placing their ends together without any special shaping. The name "butt joint" comes from the way the material is joined. The butt joint is the simplest joint to make since it merely involves cutting the material to the appropriate length and butting them together. It is also the weakest because unless some form of reinforcement is used, it relies upon glue or welding alone to hold it together. Because the orientation of the material usually presents only one end to a long gluing or welding surface, the resulting joint is inherently weak.

<span class="mw-page-title-main">Hole saw</span> Cylindrical saw used to quickly cut holes

A hole saw, also known as a hole cutter, is a saw blade of annular (ring) shape, whose annular kerf creates a hole in the workpiece without having to cut up the core material. It is used in a drill. Hole saws typically have a pilot drill bit (arbor) at their center to keep the saw teeth from walking. The fact that a hole saw creates the hole without needing to cut up the core often makes it preferable to twist drills or spade drills for relatively large holes (especially those larger than 25 millimetres. The same hole can be made faster and using less power.

<span class="mw-page-title-main">Pocket-hole joinery</span>

Pocket-hole joinery, or pocket-screw joinery, involves drilling a hole at an angle — usually 15 degrees — into one work piece, and then joining it to a second work piece with a self-tapping screw.

<span class="mw-page-title-main">Sex bolt</span>

A sex bolt is a type of mating fastener (nut) with a barrel-shaped flange and protruding boss that is internally threaded. The bolts sits within the components being fastened, and the flange provides the bearing surface. The sex bolt and accompanying machine screw sit flush on either side of the surfaces being fastened.

<span class="mw-page-title-main">Wall plug</span>

A wall plug, also known as an anchor (US) or "Rawlplug" (UK), is a fibre or plastic insert used to enable the attachment of a screw in material that is porous or brittle or that would otherwise not support the weight of the object attached with the screw. It is a type of anchor that, for example, allows screws to be fitted into masonry walls. In US English, mentions of drywall anchors are sometimes meant to refer specifically to the type of plastic wall plugs with expandable wings for hollow walls, in contradistinction with mollies and toggle bolts.

<span class="mw-page-title-main">Anchor bolt</span> Connection elements that transfer loads and shear forces to concrete.

Anchor bolts are used to connect structural and non-structural elements to concrete. The connection can be made by a variety of different components: anchor bolts, steel plates, or stiffeners. Anchor bolts transfer different types of load: tension forces and shear forces.

<span class="mw-page-title-main">Threaded insert</span> Fastener element inserted into a hole to provide threading for screws

A threaded insert, also known as a threaded bushing, is a fastener element that is inserted into an object to add a threaded hole. They may be used to repair a stripped threaded hole, provide a durable threaded hole in a soft material, place a thread on a material too thin to accept it, mold or cast threads into a work piece thereby eliminating a machining operation, or simplify changeover from unified to metric threads or vice versa.

<span class="mw-page-title-main">Screw</span> Type of fastener characterized by a thread wrapped around a cylinder core

A screw and a bolt are similar types of fastener typically made of metal and characterized by a helical ridge, called a male thread. Screws and bolts are used to fasten materials by the engagement of the screw thread with a similar female thread in a matching part.

In manufacturing, threading is the process of creating a screw thread. More screw threads are produced each year than any other machine element. There are many methods of generating threads, including subtractive methods ; deformative or transformative methods ; additive methods ; or combinations thereof.

<span class="mw-page-title-main">Screw extractor</span>

A screw extractor is a tool for removing broken or seized screws. There are two types: one has a spiral flute structure, commonly called an easy out after the trademarked name EZ-Out; the other has a straight flute structure.

References

  1. Skates, Scott - Saws on (2023-02-09). "How to Drill Pilot Holes (Why, When & Correct Size)". Saws on Skates. Retrieved 2023-06-13.
  2. Jackson, Vineta (2022-11-09). "How to Drill Pilot Holes for Wood Screws". The Handyman's Daughter. Retrieved 2023-06-13.
  3. Eckman, MaryLouise (2023-02-03). "Pilot Holes Guide". All Points Fasteners. Retrieved 2023-06-13.
  4. TAPCON reference material retrieved 2013AUG9