Cutting and drilling metal, even in a home workshop, is not especially difficult, but it does require attention. There are two main enemies: the heat produced by heavy friction between tool and metal, and the swarf that gets in the way of the cutting edge.
WD-40 Specialist Cutting Oil is made for exactly this. It is a blend of mineral oils with extreme-pressure additives that reduces friction, draws heat away from the cutting zone and cuts wear on drill bits, saw blades and taps.
What you will need
Important: Cutting oil is not used with angle grinders or abrasive discs. Always clamp the workpiece securely, wear safety glasses and never clear swarf with bare hands.
Step 1
Set the right speed
Metal, especially hard steel, is cut and drilled at low speed. The simple rule: the larger the drill diameter, the lower the speed. Excessive speed is the most common reason both the workpiece and the tool overheat.
Overheating changes the structure of the cutting edge: the bit turns blue, goes blunt and can snap. The job of cutting oil is to keep the temperature from ever reaching that point.
Step 2
Apply oil to the work area
As soon as you start drilling or cutting, apply a moderate amount of WD-40 Specialist Cutting Oil right where the tool meets the metal, then carry on working. On long cuts or deep holes, top it up several times.
The two-position straw lets you switch between a wide spray for flat surfaces and a precise jet into a hole in a single movement.
Step 3
Tap threads with oil
When cutting threads with a tap or die, wet both the tool and the hole with oil. Turn half a turn forward and a quarter back to break the swarf: the thread comes out clean and the tap does not jam.
Step 4
Get a cleaner finish on aluminium
On aluminium and soft alloys the oil also improves the finish. Fine swarf stays suspended in the fluid film and, instead of sticking to the edge, acts as a gentle smoothing agent, so the edge of the hole comes out neater.
Step 5
Do not use oil with an angle grinder
When metal is cut with an angle grinder, no lubricant is needed. An abrasive disc is designed to wear away gradually, and oil would only hinder it and clog the disc.
Step 6
Clean up and protect your tools
After the job, wipe the workpiece and tools with a rag and brush away the swarf. Wipe drill bits and taps with WD-40 Multi-Use before storing them so they do not rust in a damp workshop or garage.
Tip: If thick smoke rises from the hole and the swarf turns blue, lower the speed and add more oil. You can read the correct setting from the swarf: it should come off bright and in long curls.
What next
Using cutting oil regularly noticeably extends the life of drill bits, saw blades and taps and improves the quality of the finish. To protect stored tools from corrosion, keep WD-40 Multi-Use close by.
These uses come from the experience of WD-40 users in many countries. Always follow the instructions and warnings on the product label.
More guides in «How to use».