Structural Steel
All HMT tooling in this category is suitable for common grades of steel.
HMT COUNTERSINKS – TECHNICAL GUIDE
This guide covers material suitability, machine selection, material thickness, lubrication, adapters, best practice and recommended spindle speeds for HSS and TCT countersinks.
Which Materials Can HMT Countersinks Be Used On?
Hardened Steel
Countersinking some grades of hardened steel is feasible in controlled situations.
For best results, the HMT Ultra tooling range is recommended.
Hardened or heat-affected materials may require higher torque, reduced RPM and feed rates, and additional coolant.
Stainless Steel
Suitable for harder materials such as stainless steel when used at reduced RPM.
Non-Ferrous Metals
All HMT tooling in this category is suitable for non-ferrous materials.
Which Machine Should I Use for Countersinking?
| Machine | Suitable? | Guidance |
|---|---|---|
| Impact Wrench | Limited use | Versadrive Countersinks are suitable for light chamfering and deburring using an impact wrench. For full-depth countersinking, use a rotary drilling machine. |
| Rotary Pistol Drill | Yes | Versadrive Countersinks and DrillSinks can be used in pistol drills with a suitably low RPM. |
| Compact Magnet Drill | Limited | Compact magnet drills are normally single speed and are generally best suited to smaller countersinks, typically below approximately 20 mm diameter. |
| Large Magnet / Pillar Drill | Yes | Optimum life and performance will generally be achieved using magnetic drills or pillar drills at suitable low spindle speeds and high torque. |
What Material Thickness Can HMT Countersinks Be Used On?
Sheet Metal
Up to 4 mm
Standard Plate
5–12 mm
Medium Plate
12–25 mm
Heavy Plate
Above 25 mm
HMT Countersinks are suitable across all four material-thickness categories.
Which Cutting Lubricant Should I Use for Countersinking?
SpeedLube
Recommended for general-purpose countersinking applications.
BioCut Paste
Recommended for overhead drilling and other applications where liquid lubricant is not suitable.
BioCut Blue
Not generally recommended for general-purpose countersinking.
Recommended for harder steels and stainless steels where heat reduction is critical.
It is also a suitable choice where the material is to be welded or galvanised.
Which Adapters Can I Use With HMT Countersinks?
Impact Adapters
Versadrive Countersinks and DrillSinks up to approximately 16 mm diameter can be used with suitable impact wrenches and impact drivers.
Pistol Drill / Chuck
The Versadrive hex shank fits into a standard drill chuck.
Versadrive extension arbors can also be used where additional reach is required.
Weldon Adapters
HMT Countersinks are suitable for use in magnetic drills with the appropriate arrangement.
Morse Taper Adapters
Versadrive Countersinks and DrillSinks can be adapted for use in Morse Taper drilling machines with the appropriate adapter.
HMT Countersink Best Practice
Do I need a pilot hole or centre punch?
Not applicable for standard countersinking. The countersink is normally used on an existing drilled hole.
What is the correct feed pressure?
Apply firm, steady feed pressure throughout the cut.
Excessive feed pressure can increase heat build-up and reduce tool life.
How many holes can I expect a countersink to last?
There is no fixed number. Tool life varies depending on material, diameter, spindle speed, feed pressure, lubrication, machine condition and application.
How can I prevent chipping or breakage?
Avoid lateral movement or tilting.
Do not use excessive feed pressure.
Apply steady feed pressure and keep the tooling square to the cut.
Maintain a consistent flow of swarf.
Do not allow the countersink to vibrate over swarf while cutting, as this can cause chatter and ultimately chip or blunt the cutting edge.
How can I improve countersinking accuracy and finish?
Where possible, use a piloted countersinking system.
Piloted countersink tools such as HMT MultiSink help prevent movement of the countersink while rotating and can significantly improve countersinking performance and finish.
Recommended RPM for HSS Countersinks
Recommended spindle speed varies according to countersink diameter and material type.
| Diameter Range | Structural Steel – 10 m/min | Hardened Steel – N/A | Stainless Steel – 6 m/min | Non-Ferrous – 28 m/min |
|---|---|---|---|---|
| 6–8 mm | 400–745 | N/A | 200–425 | 995–1855 |
| 9–12 mm | 265–495 | N/A | 135–285 | 665–1240 |
| 13–17 mm | 185–345 | N/A | 95–195 | 470–855 |
| 18–22 mm | 145–250 | N/A | 70–140 | 360–620 |
| 23–30 mm | 105–195 | N/A | 55–110 | 265–485 |
| 31–40 mm | 80–145 | N/A | 40–80 | 200–360 |
| 41–55 mm | 60–110 | N/A | 30–60 | 145–270 |
| 56–80 mm | 40–80 | N/A | 20–45 | 100–200 |
Recommended RPM for TCT Countersinks
TCT countersinks use different cutting speeds from HSS countersinks. Select the appropriate spindle speed according to cutter diameter and material.
| Diameter Range | Structural Steel – 12.5 m/min | Hardened Steel – 7 m/min | Stainless Steel – 8 m/min | Non-Ferrous – 35 m/min |
|---|---|---|---|---|
| 32–35 mm | 115–125 | 65–70 | 75–80 | 320–345 |
| 36–40 mm | 100–110 | 55–65 | 65–70 | 280–310 |
| 41–45 mm | 90–100 | 50–55 | 55–60 | 250–270 |
| 46–55 mm | 70–85 | 40–50 | 45–55 | 195–240 |
| 56–63 mm | 60–70 | 35–40 | 40–45 | 170–200 |
| 64–72 mm | 50–60 | 30–35 | 35–40 | 145–175 |
| 73–80 mm | 45–50 | 25–30 | 30–35 | 130–150 |