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6.3mm x 46mm HSS Cobalt 3 Flute 90° Countersink Bit (Range: 1-6.3mm) Alpha CS3-6.3
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| Price for each item | Subtotal | % savings | ||
| Buy 1 | Buy 1 | $38.00 each | $38.00 | - |
| Buy 2 + | Buy 2 - 4 | $34.00 each | $68.00 | 10.53% |
| Buy 5 + | Buy 5 + | $32.00 each | $160.00 | 5.88% |
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In Stock
Other Sizes in Range
Delivery Information
Orders under $30 (Bulky items sent as parcel for FREE)
- Aust Post UNTRACKED Letter – FREE
- Parcel – From $8
- Express – From $10
- Click and Collect – 2hrs
Orders over $30
- Parcel – FREE
- Express – From $10
- Click and Collect – 2hrs
5% Off
10% Off
15% Off
| System of Measurement | Metric |
|---|---|
| Product | 3 Flute 90° Countersink Bit |
| Shank (h) | 5mm |
| Size | M6.3 (6.3mm) |
| Material | Cobalt High Speed Steel |
| Length (l) | 46mm |
| Head Diameter (a) | 6.30mm |
| Suitable For | Mild Steel, Aluminium, Hardwood and Hard Plastic |
| Countersink Angle | 90° |
| Min to Max Drill Range | 1.00 - 6.30mm |
| Brand | Alpha |
Dimensional data is a guide only. Tolerance differences exist between brands and batches
About Countersinking Bits
Countersinking bits cut the recessed cone that lets a countersunk-head fastener sit flush with the workpiece surface. BNA stocks HSS Cobalt 3 Flute 90-degree countersinks with 1/4-inch Hex Quick Change shanks, 13mm to 20.5mm. Three flutes cut with lower chatter than single-flute or 5-flute alternatives; the quick-change shank fits standard impact-driver holders.
Frequently Asked Questions
Standard for any project with countersunk fasteners (CSK Bolts, Wood Screws, Self Tappers). Drill the clearance hole first, then run the countersink in the same spot until the rim of the cone matches the bolt-head diameter. Slightly deeper than flush is a workshop finish, slightly proud is a tradie finish.
All metric CSK fasteners use a 90 degree included head angle. Imperial countersunk under UNC, UNF and similar standards use 82 degrees. Match the countersink to the fastener or the head will sit proud or below flush. BNA's standard countersink range is 90 degrees.
A 1-flute countersink (zero-flute cross-hole style) is fastest but chatters on stainless and hard plate. A 5-flute is smooth but slow and the flutes pack with chips in soft timber. A 3-flute is the everyday compromise. Good cut speed, controlled chatter, easy to clear.
Look at the bolt head OD on the spec sheet (typical: M6 CSK head ~12mm, M8 ~16mm, M10 ~20mm). Countersink until the cone rim matches that diameter. A pilot ring on the bit or a depth stop on the drill gives consistent depth across a batch.
Stainless work-hardens if the cutting edge dwells. Keep the bit moving forward, never let it grind in one spot. A drop of cutting fluid on the cone keeps temperatures down. If the metal changes colour (straw, blue, purple), the bit is overheating. Back off RPM and pressure.
A combo bit has the twist drill ahead of the cone cutter, so one plunge does both. Faster for repetitive work like deck screws or cabinet work. The trade-off is one geometry for one bolt size. Drill the clearance hole separately if you need flexibility.
Quick pick for Countersinking Bits:
If you are drilling: Hardened steel, cast iron, stainless steel, high-tensile work
Pick: Alpha Cobalt
Cobalt content lets the cutting edge run hotter without dulling. Where plain HSS anneals within a few holes in stainless, Alpha Cobalt cuts cleanly through hundreds. The standard upgrade for hardened steel, cast iron, stainless and high-tensile work.
Material & Coating
HSS Cobalt M35 M35 high-speed steel with 5 percent cobalt addition. The cobalt content lifts the operating temperature range to approximately 700 degrees C, so the cutting edge survives stainless and hardened workpieces where standard HSS would anneal within a few holes.
Grade selection Stainless steel (304, 316, duplex), hardened plate, alloy steels and exotic metals like Inconel. The right choice when standard HSS is failing within a hole or two. Pays for itself in stainless work by lasting many times longer.
Important Cutting fluid is non-negotiable in stainless. Run 30 to 40 percent slower than mild steel. Keep the bit moving forward; stainless work-hardens if the cutting edge dwells in one spot.
Resources
For full technical data including key product information, range and a CAD drawing, see our Technical PDFs library.
Convert between metric and imperial sizes, gauge to mm, decimal to fraction and TPI to pitch with our measurement conversion calculators.
Not sure what 1/4" is in mm (or vice versa)? See our metric to imperial chart for the conversion every drill-bit size customers ask about.
About the Brand
Alpha · Sheffield Group · Australian
Alpha is the Sheffield Group's premium drilling, cutting and fastening brand. Australian-owned, Sheffield has supplied industrial and trade markets since 1957 and is one of the country's largest distributors of cutting tools and accessories.
Range: The Alpha range covers Gold Series HSS jobber drill bits, HSS Cobalt drill bits, Bi-Metal Cobalt holesaws, TurboBORE spade bits, heavy-duty timber augers, SDS Plus masonry bits, countersinks, ONSITE+ impact-rated step-tip drill bits, and the ThunderMax range of impact-driven accessories.
Positioning: Premium-quality, production-grade tools at trade pricing. Same-day dispatch from BNA Brisbane.
Pricing & Delivery
Includes GST, a Tax Invoice and Free Standard Delivery anywhere in Australia.
Buy with Confidence
15+ years selling online · 25,000+ stock lines · 200 million pieces ex-stock in Brisbane QLD.
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Technical data Researched and compiled from numerous industry sources for the sole purpose of providing basic information. All material is advisory only and its use by anyone is entirely voluntary. Reliance on it for any purpose by anyone is at the sole risk of that person, and Bolt and Nut Australia is not responsible for any loss, claim or damages arising therefrom. In developing this information, Bolt and Nut Australia has made a determined effort to present it accurately.
Measurements Sizes are taken from supplier catalogues or hand-measured and should be used as a guide. Minor variation between batches is normal. We only stock Alpha for this product; substituting another brand is rare and would always be confirmed with you first.
Product Photos & PDF Data Sheets Represent the product type, not exact size. PDFs are a reference guide only. Specifications may change without notice.
If you see any problems with any of our specifications or you require additional information please contact us.
Delivery
Weigh less than 500grams
Exceptions: Tools, Kits, Bulky items = Sent as a parcel with tracking
Small orders that fit into the slot of your Letterbox are sent:
FREE with Aust Post Letter delivery with NO TRACKING and delivery between 4-12 business days
Or
Select a Quicker delivery service
- $7.00 Parcel Delivery 2-7 business days
- From $12.00 Express Delivery 1-4 business days
- From $14.00 StarTrack PREMIUM Express Delivery 1-3 business days
Or
Click & Collect - Warehouse pickup
Unit 9, 93 Rivergate Place, Murarrie, QLDPlace your order online and we will have it ready within 2 hours. Call if required sooner
Pickup times between 8am - 4pm, Monday - Friday
Weigh more than 500grams
Included is orders under $30 but weigh more than 500grams or wont fit in the slot of your letterbox
Including Large and Bulky heavy orders are sent:
FREE as a Parcel Delivery WITH TRACKING and delivery between 2-7 business days
Or
Select an Express delivery service
- From $12.00 Express Delivery 1-4 business days
- From $14.00 StarTrack PREMIUM Express Delivery 1-3 business days
Or
Click & Collect - Warehouse pickup
Unit 9, 93 Rivergate Place, Murarrie, QLDPlace your order online and we will have it ready within 2 hours. Call if required sooner
Pickup times between 8am - 4pm, Monday - Friday
Further delivery information can be found on our Delivery page
Supplier Details
| MPN | CS3-6.3 |
| UPC | 9342386002690 |
