Screwdrivers

The first screwdrivers appeared about the middle of the seventeenth century. In English, French and Dutch they were and are called "turnscrews" or the equivalent. In most other European languages they are known as "screw-pullers" or "unscrewers". The first use of the word "screwdriver" occurs in an order by a Philadelphia merchant to a London dealer in 1760 to supply "Cuttoes (hunting knives).., with screwdrivers". This American term has now superseded the old English form "turnscrew".

Types of handle

Traditional screwdriver handles swell out, forming a bulbous end, which fills the hand to provide a better grip and enable the user to provide more torque at the driving end. They are made in plastic or hardwood. The wooden variety is strengthened with a metal ferrule where the blade enters the handle, whereas plastic handles are moulded around the blade to provide a much stronger fixing.

Straight fluted handles are also made in plastic or hardwood. The fluting is presumably intended to provide even more grip, but in fact the smooth bulbous surface provides a greater area of surface contact between hand and tool. A slip-on rubber grip is available, which increases the size of the fluted handle.

There is also a very strong screwdriver with a one-piece blade and handle, formed by riveting hardwood grips to each side of the blade, which runs the length of the tool.

Types of screwdriver tip

CABINET TIP, FLARED TIP

The most common screwdriver has the familiar flat tip designed to drive a slotted head screw. The end of a round or square sectioned blade is flared out and tapered by grinding down on both sides. The tip is ground square and is often narrowed by grinding back the points of the flared tip.

PARALLEL TIP

This is used on the same type of screw as a cabinet tip, but the end does not flare out The round sectioned blade is tapered and ground square at the tip. The blade of a screwdriver with this type of tip can turn a screw at the bottom of a hole or in other restricted spaces, and is commonly used in electrical or electronic work.

PHILLIPS HEAD

This is a cross head tip formed by grinding four flutes in the end of a pointed blade to increase the grip between the tool and the screw.

POZIDRIV HEAD

This tip is similar to a Phillips head, but designed to fit into an additional square hole in the centre of the crossed slots on the screw head.

REED AND PRINCE

Another cross head tip similar to Phillips and Pozidriv, but the flutes are ground square and the tip comes to a sharp point. Used on many Japanese and Asian products.

OTHER TYPES OF HEAD

Several other types of screwdriver tips have been designed to provide a more positive location in the screw head. Some examples are:

CLUTCH HEAD

ROBERTSON

and TORX.

Care of screwdrivers

Choose a screwdriver which is correctly ground and the right size to fit snugly in the screw-head. A rounded, chipped or undersized tip will slip and damage either the screw slot or the work itself. Similarly avoid using a tip that is too large and projects from cither side of a countersunk screw. This will damage the work as the screw is driven home.

Use the correct cross head driver to fit the screw. Using a straight tip or another make of cross head can damage the screw, and once a cross head screw has been damaged it is very difficult to remove.

Make sure that driver tips fit properly into screw heads, as shown above.

A tip that is too large (above left) will damage surrounding work; a tip that is too small will not grip the screw correctly.

Removing a seized screw

To do this you may need a large powerful screwdriver. If the blade is too large to fit the screw head, grind the corners until the blade fits the slot.

Repairing a straight edged screwdriver

Grind the side of the tip on an oilstone, keeping the blade at the correct angle.

Alternative grinding method

You can regrind a straight tipped screwdriver on an emery wheel, although this is not recommended by every manufacturer.

Cabinet Screwdriver

SIZE: Blade: 3 to 10in.

MATERIAL: Blade: steel: Handle: beech, boxwood

USE: To drive wood screws and slotted machine screws

The cabinet screwdriver is the woodworker's traditional driver. The hardwood handle is oval in section, swelling out to fit the palm of the hand. The cylindrical blade flattens where it enters the ferrule, whereas the blade of the present day counterpart often extends throughout the handle. The flared tip of the blade is sometimes ground back into a taper.

London Pattern

SIZE: Blade: 6 to 12in.

MATERIALS: Blade: steel; Handle: beech.

USE: To drive wood screws and slotted machine screws

The London pattern is a large screwdriver, characterized by its flat waisted blade and beechwood handle with flats on two sides. These flats were probably designed to fit the palm of the hand and also to prevent the driver rolling off the bench. London pattern screwdrivers are not common in the average workshop today. They are normally reserved for the occasional job where considerable torque is required, which can only be supplied by a big screwdriver.

Electrician's Screwdriver

SIZE: Blade: 3 to 10in.

MATERIAL: Blade: steel; Handle: plastic

USE: To drive machine screws in electrical work

The electrician's screwdriver has a long thin cylindrical blade with a parallel ground tip. The plastic handle insulates the user. Some drivers are further insulated by a plastic tube running down the length of the blade.

Spiral Ratchet Screwdriver

OTHER NAMES: "Yankee" ratchet screwdriver, pump screwdriver

SIZE: Extended blade length with bit: 9-5/8 to 28in.

MATERIAL: Various

ACCESSORIES: Standard bits, cross head bits, chuck adaptors, countersink bits

USE: To drive screws automatically

This tool drives screws by pressure. The spiral grooves along the length of the screwdriver blade produce a turning force at the tip when pressure is applied to the handle. The spring-loaded handle returns when pressure is released. The action is consequently much faster than that of a standard screwdriver which relies on the twisting action of the human arm, so the spiral screwdriver is very useful when a lot of turnings are involved in a job.

Clockwise or counterclockwise action can be selected by means of a thumb slide on the ferrule or the mechanism can be locked to convert the driver to a standard screwdriver action. A knurled ring at the end of the ferrule will lock the blade in the fully extended or retracted positions, where it will act like a standard ratchet driver.

A pilot hole is essential for the most efficient action, although screws can be driven unpiloted into softwood where the finish is unimportant.

Fitting a bit

The standard bit has a notch in the shank which engages in the chuck to hold it in place. With the blade locked, pull back the knurled chuck, insert the bit and release the chuck.

Bit types

A variety of bits is available to fit the chuck of the driver, including drill points.

Using the driver

Take advantage of the spiral ratchet's fast action when working on complex fittings like a door lock.

Voltage Tester

OTHER NAMES: Spark detecting screwdriver, mains tester

SIZE: Various

MATERIAL: Various

USE: To test for the presence of an electrical current

The voltage tester is an electrician's screwdriver with an insulated blade and handle-By keeping a finger on the metal terminal at the end of the handle and placing the tip on a live terminal, a circuit is completed and a neon bulb in the handle lights up if electrical power is present.

Testing voltage

Touch a live terminal with the tester's tip. A resister in the handle prevents shocks.

Stubby Screwdriver

SIZE: Blade: 1 and 1-1/2in.

MATERIAL: Blade: steel; Handle: hardwood, plastic

USE: To drive screws in restricted space

The stubby screwdriver has a short blade for use in confined spaces. Its main feature is the enlarged handle which provides enough grip to produce efficient torque. A stubby screwdriver can be fitted with a tommy bar in the handle for increased torque. Stubbys are manufactured with all the various types of tips.

Ratchet Screwdriver

SIZE: Blade: 3 to 8in.

MATERIAL: Blade: steel; Handle: hardwood

USE: To drive screws without altering the grip

The ratchet enclosed in the ferrule of this screwdriver allows the user to drive a screw without changing his grip. A thumb slide adjusts the action to drive clockwise or anticlockwise as well as to remain fixed in either direction. The smaller sizes are fitted with a knurled ring which can be turned, using forefinger and thumb, to drive the blade when starting screws.

Offset Screwdriver

OTHER NAMES: Round the corner screwdriver, cranked screwdriver

SIZE: Blade: 3 to 6in.

MATERIAL: Steel

USE: To drive screws inaccessible to a standard screwdriver

The offset driver is used where there is insufficient room to use a conventional screwdriver. It is also good for applying extra torque to a stubborn screw.

The driver is simply a steel bar, either hexagonal or round in section, with the ends bent at right angles and ground to form a screwdriver tip. It is double ended and can be used for cross head or slotted head screws. In the latter case one tip is in line with the bar while the other is at right angles to it. Combination cross head and slotted head drivers are also manufactured.

Offset Ratchet Screwdriver

SIZE: Blade: 3-7/8 to 4-3/4in.

MATERIAL: Steel

USE: To drive screws in a confined space

The offset ratchet screwdriver performs the same function as the standard offset driver with the advantage of a ratchet mechanism that allows the screw to be driven without having to remove the tip from the screw head. Clockwise or counter clockwise action can be selected by moving a lever in the stock of the tool.

The drivers have two sizes of tip of either the conventional slotted head or the cross head variety; alternatively, there may be one of each head. Modern versions are available with interchangeable bits.

Jeweler's Screwdriver

OTHER NAME: Instrument maker's screwdriver

SIZE: Length: 4-1/4in.; Blade width: 0.025 to 0.1in.

MATERIAL: Blade: steel; Body: various

USE: To drive very small screws

The jeweler's screwdriver is used by watchmakers, opticians, model makers, or any other kind of fine instrument maker. They are either made in sets with fixed blades or as one holder with a selection of interchangeable blades.

Using the driver

The driver is held vertically between fingers and thumb with the index finger resting on the revolving head. With the tip located in the screw the body is revolved while pressure is applied by the index finger.

Screwdriver Bit Holder

SIZE: Blade: 3-1/4in.

MATERIAL: Shaft: steel; Handle: wood, plastic

USE: To hold and drive interchangeable tips

The bit holder is a screwdriver type handle fitted with a hollow ended shaft into which various screwdriver tips can be inserted.

 

Power Screwdriver Bit

SIZE: Various

MATERIAL: Steel

USE: To drive screws with a variable speed electric drill

Power screwdriver bits have hexagonal shafts to fit in the chuck of an electric drill and tips suitable for slotted head and cross head screws.

A magnetic bit holder is available for any short hexagonal sectioned tips.

Impact Driver

SIZE: 5-1/2in.

MATERIAL: Steel

ACCESSORIES: Screwdriver bits, socket set

USE: To free tight screws or nuts

The impact driver is used to free screws or nuts which have seized. The square drive fits socket heads and, with an adaptor, drives replaceable bits for both slotted and cross head screws.

With the tool in position on the nut or in the screw head, strike the end with a hammer. Inside the handle is a mechanism which converts the blow into torque to break free a tight fitting. By twisting the handle, clockwise or counterclockwise movement can be selected.