TAPER PLUG AND RING GAUGES TO BS21 AND 1S07/2
Gauges for testing pipe threads where pressure
tight joints are made on the threads to
BS 21: 1985, and ISO 7/2 1982.
BS 21 specifies requirements of pipe
threads for joints made pressure tight by the mating of threads, and are taper
external, taper internal, parallel external and parallel internal threads.
The thread form is based on the Whitworth profile. The taper is 1:16 on diameter,
normal to the axis.
The pipe fittings range in size from 1/16 to 6.0.
There are two systems for gauging pipe threads specified in this standard.
System A gauges are intended for use
where there are additional production control methods to ensure accuracy of
the threads. System B gauges are intended
for use where there may be no other adequate method of production control.
System A comprises two types of gauge. A taper full form
screw ring, and a taper full form screw plug.
When gauging taper external threads with the taper full form screw ring, the
small end of the product thread should lie within the plus and minus tolerance
of the small end of the ring.
When gauging taper or parallel internal threads with the taper full form plug,
the end of the product thread should lie within the plus and minus tolerance
from the gauge plane step of the plug.
System B comprises four types of gauge.
A taper full form screw ring, a taper full form screw plug, a taper plain
ring, and a taper plain plug.
When gauging taper external threads with the taper full form ring or with
the taper plain ring, the small end of the product thread should lie between
the faces, or flush with either face of the step on the gauge.When gauging
taper or parallel internal threads with the taper full form screw plug or
with the taper plain plug, the end face of the product should lie between
the faces, or flush with either face of the step on the gauge.
When using any of the above gauges, assembly should be handtight only, taking
care not to use excessive force.
Designations
External taper threads and taper ring gauges are designated R (1/4)
Internal taper threads and taper plug gauges are designated Rc (1/4)
| Size |
||
| Plug Rc |
Ring R |
|
| 1/16 | 0480 | 0481 |
| 1/8 | 0482 | 0483 |
| 1/4 | 0484 | 0485 |
| 3/8 | 0486 | 0487 |
| 1/2 | 0488 | 0489 |
| 3/4 | 0490 | 0491 |
| 1 | 0492 | 0493 |
| 1 1/4 | 0494 | 0495 |
| 1 1/2 | 0496 | 0497 |
| 2 | 0498 | 0499 |
Go/Not Go parallel screw rings can be supplied to test special parallel external threads for gas appliances where pressure tight seals are made on machined faces. The size range for threads is 1/8 to 2.0. These threads are designated Rs (1/4)
Go/Not Go parallel screw plugs can be supplied to test parallel internal
threads.
The manufacturing limits for these parallel gauges will be as specified in
BS 919: Pt. 2: 1971.
ISO 7/2 specifies one gauging system only for
testing pipe threads.
The standard specifies three types of gauge. A full form taper screw ring,
a full form taper screw plug, both used for testing the product thread, and
a modified form taper screw check plug for testing the ring during manufacture,
and for testing wear following use.
Whilst the gauges in this standard are manufactured to the same basic product
diameters as the BS 21 pipe thread, and are designed to carry out the same
gauging function, there are differences in design, and differences in the
gauge manufacturing limits.
| Size |
||
| Plug Rc |
Ring R |
|
| 1/16 | 0480 ISO | 0481ISO |
| 1/8 | 0482 ISO | 0483 ISO |
| 1/4 | 0484 ISO | 0485 ISO |
| 3/8 | 0486 ISO | 0487 ISO |
| 1/2 | 0488 ISO | 0489 ISO |
| 3/4 | 0490 ISO | 0491 ISO |
| 1 | 0492 ISO | 0493 ISO |
| 1 1/4 | 0494 ISO | 0495 ISO |
| 1 1/2 | 0496 ISO | 0497 ISO |
| 2 | 0498 ISO | 0499 ISO |
Because of these differences
care should be taken |
