FREE Delivery
Australian Owned
Spend DISCOUNTS
All Categories
Abrasive Block 
Cutting Disc 
Flap Disc 
Grinding Disc 
Hand Pads 
Quick Change Roloc Disc 
Sanding Disc 
BSF 
Left Hand Thread 
Metric Coarse 
Bolts 
Cotter Pins 
Farm Bolt Packs 
Machine Screws 
Nuts 
Nutserts 
Rivets 
Security Screws 
Self Drilling Screws 
Self Tapping Screws 
Socket Screws 
Timber Screws 
Washers 
Coach Screws 
Cup Head Coach Bolts 
Eye Bolts 
Furniture Connector JCB Bolts 
Hex Bolts & Set Screws 
Hex Flange Bolts 
Left Hand Thread Hex Bolts & Set Screws 
Mushroom Head Roofing Bolts 
Plow Bolts 
Purlin Flanged Bolts 
Sems 
Structural K0 Bolts & Nuts 
Auger Bits Heavy Duty 
Combination Drill & Taps 
Countersinking Bits 
Decking Tools 
Drill Sets 
Hex Drive Drill Bits 
Holesaws and Accessories 
Jobber Drill Bits 
Left Hand Drill Bits and Screw Extractors 
Long Series Drill Bits 
Masonry Drill Bits 
ONSITE+ Impact Step Tip Drill Bits 
ONSITE+ Step Tip Step Cutters 
ONSITE+ Step Tip Step Drills 
ONSITE+ Step Tip Reduced Shank Drill Bits 
ONSITE+ Step Tip Long Series Drill Bits 
ONSITE+ Step Tip Combination Drill & Tap 
Reduced Shank Drill Bits 
Single and Double Ended Drill Bits 
Spade Bits 
ThunderMAX 
Autofeed Gun Bits 
Bit Holders 
Drywall Bits 
Hex Bits 
Keys 
Nutsetters 
Phillips Bits 
Post Hex Bits 
Post Torx Bits 
Pozi Bits 
Slot Bits 
Snake Eye Bits 
Socket Adapters 
Square Bits 
Torx Bits 
Tri-Lobular Bits 
Barrel Nut 
Countersunk Timber Screws 
Cross Dowel Nut 
Furniture Connector JCB Bolts 
Tee Nut 
Timber Insert Nut 
Button Flange Head 
Button Head 
Cap Head 
Cheese Head 
Countersunk Head 
Mushroom Head 
Pan Head 
Raised Head 
Round Head 
Sems 
Thread Rolling Screws 
Wing Head 
Cast Snap Hook 
Conduit Saddles 
Dee Shackles 
Double Thread Lag Screws 
Eye Nuts 
Hinges 
Hose Clamps 
Lag Eye Screws 
Linch Pins 
Pad Eyes 
Rigging Screws 
S Hooks 
Saddle Eye Straps 
Spring Hooks 
Swivels 
Toggle Latches 
Turnbuckles 
U Bolts 
Accessories 
Bremick MultiONE® 
Chemical Adhesives 
Chemical Studs & Capsules 
Countersunk Screw Anchors 
Countersunk Sleeve Anchors 
Dome Torx Screw Anchors 
Drop in Anchors 
ETA Approved Anchors 
Eye Screw Anchors 
Hex Flange Screw Anchors 
H-IT Anchors 
Hollow Wall Anchors 
Masonry Drill Bits 
Metal Pin Anchor 
Mungo Frame Anchors 
Mungo Plugs 
Nylon Nail-In Anchor 
Packers 
Plasterboard Plugs 
Plastic Sleeves 
Self Tapping Concrete Screws 
Sleeve Anchors 
Spaghetti Roll 
Suspension Anchors 
Tie Down Screw Anchors 
Toggles 
Universal Screw Anchor 
Wall Plugs 
Wedge Anchors | Trubolts 
Acme Nut 
All Metal Lock Nut 
Barrel Nut 
Cage Nut 
Cap Nut 
Channel Nut 
Conelock Nut 
Cross Dowel Nut 
Dome Nut 
Eye Nuts 
Flange Nyloc Insert Nut 
Flange Nut 
Hex Head Plug Cover 
Hex Rod Coupler Nut 
Hex Standard Nut 
K-Lock Nut 
Left Hand Thread Nut 
Lock Nut Thin 
Nutserts | Rivet Nuts 
Nyloc Insert Nut 
Plow Nut 
Push Nuts 
Shear Security Nut 
Slotted Castle Nut 
Square Nut 
Slab Tee Nut 
Structural K0 Nut 
Tee Nut 
Thin Nyloc Insert Nut 
Timber Insert Nut 
Weld Nut 
Wing Nut 
Choose by Material 
Choose by Style 
Nutsert Tools 
Circlips 
Cotter Split Pins 
Dowel Pins 
Linch Pins 
Push Nuts 
R Clip Humpback Pins 
Spring Roll Pins 
Wave Spring Roll Pins 
Countersunk Standard 
Countersunk Sealed 
Dome Standard 
Dome Multigrip 
Dome Peeled 
Dome Sealed 
Dome Painted 
Large Flange Standard 
Large Flange Peeled 
Structural Dome 
Structural Countersunk 
Tools 
Screws only for Metal 
Screws only for Timber 
Decking Screw Bundles 
Decking Tools 
Bugle Batten Metal Screws 
Button Pan & Wafer Metal Screws 
Countersunk Metal Screws 
Countersunk with Wings Metal Screws 
Flat Top Metal Screws 
Hex Flange Metal Screws 
Painted Metal Screws 
Plasterboard Metal Screws 
Roofing Metal Screws 
Series 500 Metal Screws 
Bugle Batten Timber Screws 
Button & Wafer Timber Screws 
Chipboard Screws 
Coach Screws 
Countersunk Timber Screws 
Flat Top Stitching Timber Screws 
Hex Flange Timber Screws 
Landscape Timber Screws 
Painted Timber Screws 
Plasterboard & Villaboard Screws 
Roofing Timber Screws 
Machine Screws 
Nuts 
Security Bits 
Self Drilling 
Self Tappers 
Countersunk Head 
Mushroom Head 
Pan & Button Head 
Plastite Screws 
Anti-Seize 
Cutting Compound 
Glue & Adhesive 
Grease 
Pipe & Gasket 
Silicone & Sealants 
Threadlocking | Loctite 
Button Head Socket 
Countersunk Head Socket 
Low Head Socket Cap 
Shoulder Socket 
Socket Head Cap 
Socket Set (Grub) 
Die Nuts 
Taps 
Tap Wrenches 
Adhesive Guns 
Blades 
Decking Tools 
Drop In Anchor Tools 
Hex Allen Keys 
Hollow Wall Anchor Tools 
Knives 
Measuring Tapes & Rulers 
Scissors & Snips 
Technical Guides 
Round 
Round with Plate 
Square 
Belleville Washers 
Conical Spring Washers 
Countersunk Serrated Lock Washers 
Cup Washers 
Curved Washers 
External & Internal Tooth Lock Washers 
Flat Round Washers 
Flat Round Washers DIN125 
Flat Round Washers DIN433 Small OD 
Heavy Round Washers 
Heavy Square Washers 
High Tensile Round Washers 
Mudguard Round Washers 
Nord-Lock® Washers 
Nylon Flat Round Washers 
Red Fibre Flat Round Washers 
Roofing Screw Washers 
Schnorr® Washers 
Shoulder Washers 
Spring Lock Washers 
Structural K0 Washers 
Wave Washers Countersunk Serrated Lock Washers
Washers are named by the bolt they fit: an M10 washer suits an M10 bolt. The inside diameter is slightly larger than the bolt so it slides on. Our guide covers every size and washer type we stock.
Measure the inside diameter (ID), outside diameter (OD) and thickness, as shown in the drawing.
WHEN TO USE
Specifically designed for use with countersunk and oval head screws. Standard flat tooth lock washers don't work properly under a countersunk head because the head cone displaces the washer centre. The countersunk lock washer is shaped to match.
MATERIAL
A2-70 G304 Stainless Steel — Corrosion-resistant for outdoor and food/chemical applications.
HOW IT WORKS
Like any tooth lock washer, the radial serrations are angled so tightening forces them flat. As they flatten they bite into the mating surface and into the underside of the screw head. The result is a mechanical lock that resists rotation from vibration far better than a plain flat washer alone.
WHY AUSTRALIA TRUSTS BOLT & NUT
With 15+ years selling fasteners online from Brisbane, we hold over 25,000 stock lines and 200 million pieces — 98.75% of online orders placed before 1pm leave same day. Save more as you buy more — we offer up to 13 price breaks plus 3 spend-tier discounts. Read our customer reviews or get in touch if you need help picking the right countersunk lock washer.
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
Countersunk serrated tooth lock washers are a specialised variant of the standard tooth lock washer, with the centre hole formed as a countersunk recess to match the underside of a countersunk or oval head screw. The serrated teeth on the outer face bite into the mating surface, while the countersunk centre locks against the screw head — giving locking action without sacrificing flush appearance.
TECHNICAL RESOURCES
Need help identifying your washer? See our washer measuring guide, or check the washer gauge sizing chart.
For full sizing data and standards, see our Technical PDFs library.
