How to Drill Steel: Drill Bits, RPM, Straight Holes & Tapping

  • By Sam

Published: Monday, August 10, 2026

How to Drill Steel: Drill Bits, RPM, Straight Holes & Tapping
 

If you want to know how to drill steel, start with four things: the right drill bit, the right speed, consistent cutting pressure, and good control over the angle and depth of the hole. Steel is less forgiving than wood or plastic. Too much speed creates unnecessary heat, too little feed can make the bit rub instead of cut, and a small angle error can become much more noticeable as the hole gets deeper.

 

These are exactly the kinds of variables we wanted to make easier to control with the SPESYN Tool 3 (ST3). ST3 combines a 0–2000 RPM variable-speed drilling mode, a Front Guide Module for 90° alignment, real-time depth measurement with ±0.1 mm relative accuracy, and dedicated drilling, tapping and screwdriving modes in one handheld platform.

 

So while power matters when drilling steel, good results are usually about much more than power alone.

What Drill Bit Should You Use for Steel?

For general-purpose steel drilling, HSS high-speed steel twist drills are a common choice. HSS drill bits combine strength, heat resistance and stability, which is why they are widely used for metal drilling. Different steel grades and working conditions may require different point geometries, coatings or tool materials, so the bit should still be selected according to the material you are actually drilling.

 

A sharp bit matters just as much as its material. If the cutting edges are worn, increasing drill speed usually produces more heat rather than better cutting.

 

For handheld work, a self-centering or split-point drill can also make starting the hole easier because it reduces the tendency of the bit to wander across a smooth steel surface.

 

Before drilling, mark the hole accurately. A center punch can provide a more defined starting point, especially on flat steel plate.

What RPM Should You Use to Drill Steel?

There is no universal RPM for steel drilling.

 

The correct speed depends on the drill diameter, steel grade, drill material, coating, cooling and drilling conditions. One of the most important relationships is simple:

 

as drill diameter increases, RPM generally decreases.

 

For HSS drills, a practical cutting-speed reference for mild steel with approximately 0.2–0.3% carbon is around 80–110 SFM, while stainless steel is considerably lower at around 30–50 SFM. Professional drilling references also emphasize that feeds and speeds are guidelines rather than fixed rules because actual working conditions can require adjustment.

 

Using those cutting-speed ranges, the following table gives a useful RPM reference:

HSS Drill Diameter Mild Steel Stainless Steel
5 mm 1,550–2,130 RPM 580–970 RPM
6 mm 1,290–1,780 RPM 490–810 RPM
8 mm 970–1,330 RPM 360–610 RPM
10 mm 780–1,070 RPM 290–490 RPM
13 mm 600–820 RPM 220–370 RPM
i These RPM ranges are practical references for HSS drill bits. Actual speed should be adjusted according to the drill bit, steel grade, lubrication, hole depth, and cutting conditions.

These numbers are reference ranges, not fixed settings. The actual speed should still be adjusted according to the specific drill bit, steel grade, lubrication, hole depth and cutting behavior. If the drill-bit manufacturer provides cutting data for the exact tool, that should take priority.

 

This is one reason variable-speed control matters in steel work.

 

The ST3 drilling mode provides 0–2000 RPM variable speed, allowing the user to adapt the drilling speed to different bit diameters and materials within the rated range of the tool. ST3 uses separate operating ranges for its other functions: 0–400 RPM for tapping and 0–500 RPM for screwdriving. Its chuck capacity is up to Ø13 mm.

 

For example, the calculated mild-steel range for a 5 mm HSS bit extends slightly above 2000 RPM, but ST3 should always be operated within its rated 0–2000 RPM drilling range.

How to Drill Steel Properly

The basic process is straightforward, but every step affects the quality of the final hole:

  1. Mark the hole position accurately and use a center punch when helpful.
  2. Choose a sharp drill bit suitable for the steel, then set an appropriate starting RPM for its diameter.
  3. Keep the drill aligned with the work surface and apply steady, positive feed so the bit continues cutting instead of rubbing.
  4. Watch heat and chip formation. For thicker material, larger bits, stainless steel or deeper holes, cutting fluid and periodic chip clearing can help maintain cutting performance.
  5. Control the final depth, especially when drilling a blind hole or preparing a hole for tapping.

The goal should not be to push through the material as quickly as possible. A drill producing clean chips and making steady progress is usually in a better cutting condition than one spinning rapidly while producing mostly heat.

 

For deeper holes, chip evacuation becomes increasingly important. Published drilling guidance recommends reducing speed and feed as hole depth becomes substantially greater than drill diameter.

How Do You Keep a Steel Hole at 90°?

This is where handheld steel drilling becomes more difficult.

 

It is possible to select the correct bit and RPM and still produce a poor hole simply because the drill enters the steel at an angle. On thicker material, a small angle error at the surface becomes more obvious as the hole gets deeper.

 

Trying to judge 90° by eye is also harder than it looks. A drill can appear vertical from the side while leaning forward or backward from another viewing angle.

 

That problem was one of the reasons we developed the ST3 Front Guide Module.

 

The front guide sits against the work surface and helps keep ST3 aligned at 90° during drilling and tapping. Instead of relying entirely on hand control and visual estimation, the tool has a physical reference against the workpiece.

 

For steel plates, brackets, frames, fixtures and workshop projects, that means the operator can focus more on the actual cutting process without constantly checking whether the drill is beginning to lean.

 

This becomes even more important when the hole will later be tapped, because the tap will tend to follow the direction established by the drilled hole.

How Deep Should You Drill Steel?

For a through hole, depth is mostly determined by the thickness of the steel.

 

For a blind hole, however, knowing when to stop becomes much more important.

 

A common handheld solution is to wrap tape around the drill bit or install a depth collar. These methods can work, but they still depend on a physical mark or mechanical setup outside the hole.

 

ST3 uses real-time depth measurement instead.

 

You can place the tool at the work surface, use one-touch zeroing, and then monitor the relative drilling depth as the bit moves into the material. ST3 provides ±0.1 mm relative depth accuracy, making depth easier to control when drilling blind holes or repeating several holes to a similar depth.

 

This is particularly useful in metal fabrication because the hole often has another job to do after drilling.

 

It may need to become a threaded hole.

Drilling Steel Before Tapping

A good thread begins with a good pilot hole.

 

The hole diameter needs to match the intended thread, but the direction and depth of the hole matter too. A pilot hole drilled at an angle gives the tap an angled path to follow. A blind hole drilled too shallow may not provide enough space for the required thread.

 

For example, M6 × 1.0 commonly uses a 5 mm tap drill as a practical starting size, although final tap-drill selection should always be based on the thread requirement, workpiece material and the tap being used.

 

This is where the ST3 workflow goes beyond simply drilling steel.

 

We designed ST3 around three dedicated operations:

Drill → Tap → Drive

 

After drilling the pilot hole, the tool can switch to its dedicated 0–400 RPM tapping mode. Automatic reverse behavior assists the tapping process, while the Front Guide Module continues to help maintain alignment. Once the thread is finished, the dedicated 0–500 RPM screwdriving mode and intelligent torque control can be used for fastening.

 

Instead of treating drilling, tapping and fastening as three unrelated jobs, ST3 turns them into one connected handheld workflow.

 

That is particularly useful for brackets, custom metal parts, aluminum profiles, steel frames, fixtures and other fabrication projects where the final goal is not simply an empty hole.

Is Drilling Stainless Steel Different?

Yes.

 

The same basic principles apply, but stainless steel usually requires lower cutting speeds than mild steel when using comparable HSS tooling. The reference values above illustrate the difference: 30–50 SFM for stainless steel versus 80–110 SFM for mild steel under the referenced HSS drilling conditions.

 

Stainless steel also makes it especially important to keep the drill cutting rather than rubbing. Some stainless steels can work-harden during drilling, making the material around the cutting zone increasingly difficult to machine if the bit spends too much time rubbing against the surface.

 

That means a sharp bit, appropriate RPM, positive feed and heat management matter even more.

 

It also shows why “maximum RPM” is not the same thing as “better drilling.” The useful speed is the speed that suits the bit and the material in front of you.

Steel Drilling Is About Control, Not Just Power

A conventional cordless drill can certainly make a hole in steel.

 

But once a project requires a specific RPM, a straight 90° hole, controlled blind-hole depth, or accurate tapping afterward, drilling becomes less about simply having enough power and more about controlling the process.

 

That is the problem we built SPESYN ST3 to address.

 

Its variable 0–2000 RPM drilling mode lets you adapt speed to the work. The Front Guide Module helps maintain 90° alignment. Real-time depth measurement gives you more control over blind holes. And dedicated Drill, Tap and Drive modes allow the work to continue from the first cut to the finished thread and fastener in one handheld platform.

 

For us, precision steel drilling is not simply about making a hole.

 

It is about making the hole you actually intended to make—and being ready for whatever comes next.

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