Page 39 - Industrial Technology October/ November 2020 issue

An Introduction to Captive Screws

The available head drivers include:
Schematic Drive Types Uses
Ideal for precision assembly. Most recommended
Hexagonal Recess
where less surface area is available.

Crosshead Provides good control in driving. Always use a driver
®
(Phillips ) bit of the proper size which is in good condition.
Positive-engaging, fast-locating method which
Star Head transmits drive torque with less required downward
®
(Torx )
pressure. Good fastening appearance.
Accepts standard blade screwdriver. Requires less
downward pressure to drive parts than those with
Slotted
recessed openings. Use a proper fitting blade to
minimize slippage.

These screws are impossible to remove without
Security
the special matching screw driver.

Retaining Washers

These are simple but effective when used with our captive screws. The captive screws have
a normal thread and a reduced diameter for the rest of the screw length. The washer is
threaded internally and once screwed on to the captive screw is effectively captive. Please see this
illustrated below. Example;

Counterbore for
Counterbore for
Counterbore for
screw length
screw length
Retaining washer screw length
(threaded) Structure
Structure
Structure
Retaining washer
(threaded) Washer
Washer
Washer
shallow
shallow
shallow
thread
thread thread
Screw over
Screw over
Screw over
threaded section
threaded section
threaded section
Shallow counterbore
Shallow counterbore
Panel removed, screw retained
Panel removed, screw retained
for washer Panel removed, screw re ta ined
for washer
0333 207 4498