Skip to content
Join over 30,000 delighted customers
Join over 30,000 delighted customers

Terms Used for Screw Threads

Some General Terms Used for Screw Threads


Thread Pitch: this is the distance between threads. eg the distance between the thread crests might be 1 mm vs 1.5mm. Thread pitch is the main difference between NPT and BSP standards.

Straight vs Tapered (aka Parallel vs Dynamic) - where the diameter/thickness, starts wide and becomes thinner.

Thread Forms: The shape/form of the Thread Peaks and Thread Valleys.

Thread Peaks (aka Thread Crests) - ie the tips / top edges of the threads.

Thread Valleys (aka roots) - ie the lowest points between the threads.

Thread Flanks - the surface of the thread between the valleys and the Peaks. the angle of these is the “thread flank angle”.

Callipers - a measuring tool to determine diameter.

Diameter - the full width of a circle eg the line that goes through the middle of a circle if you were to cut it in half.

Outside Diameter - eg the outside edge-to-edge of a pipe or adapter.
Inside diameter - eg the size of the hole inside a pipe / the “borehole”.

A Thread / Pitch Gauge - a measuring tool that gives you the thread pitch etc (see above).



Related information


Our replacement adapter service

Broken Port / Adapter / Connector? Help Finding Your Replacement

Adapter size to size chart

Replacement Adapter Help

BSP vs NPT Types

Some General Terms Used for Screw Threads

Replacing Housing Adapters / Ports

Replacing Water Filter Tap Connectors

Replacing Water Supply Connectors

More about Tube Sizes

Chart of Tube Size Adapters Combinations

Recently Viewed

    Over 8,000 reasons to buy from us

    Trustpilot
    Well Established

    We are a family run business who value our customers. We've been trading for over twenty five years. So we won't be "here today gone tomorrow". Your Money Back Guarantees and Warranties will be safe.

    Fully Accredited

    Members of Safebuy the leading Consumer Assurance Scheme for online retailers approved under the Trading Standards Institute's Consumer Codes Approval Scheme.

    Repeat Customers

    Many of our clients have been buying filters from us for several years. Over 95% keep coming back to renew their filter because we offer a friendly, helpful service and great value prices. Checkout our TrustPilot reviews.

    We’re Trustworthy

    We have a huge number of great independent testimonials. For example on the Approved Consumer Code Directory for the Trading Standards Institute and on Google Certified Shops.

    Such an improvement over unfiltered water. Losing microplastics, scale, chlorine and all the other nasties that can work their way in is just a bit of piece of mind for me in relation to my kids.
    – Nick Love
    I've had the filter installed for 1 month now and the water tastes loads better and no more smell of chemicals, just clean fresh filtered water I'd say it's the best water I've ever had.
    – Neil Bradfield
    “My filter fits easy and I am happy. We weigh the old filter when it is removed, filled with gunge which never got into our bodies with this filter. It’s quite frightening. My filter is worth every penny!
    – Kathleen Gibson
    Such an improvement over unfiltered water. Losing microplastics, scale, chlorine and all the other nasties that can work their way in is just a bit of piece of mind for me in relation to my kids.
    – Nick Love
    I've had the filter installed for 1 month now and the water tastes loads better and no more smell of chemicals, just clean fresh filtered water I'd say it's the best water I've ever had.
    – Neil Bradfield