A step drill bit is a cone shaped bit with a series of stepped diameters, so one bit cuts several hole sizes in thin material. They are used mostly in sheet metal, aluminum and plastic, where a twist bit can grab or leave a ragged edge. The choices that matter are the size range, the number of steps, the coating, the shank style and whether you want a set or a single bit.
The six picks below include a 50 size set, a 3 piece impact ready set, two single Milwaukee bits and a cobalt kit. Sizes, coatings and materials come from each listing page and are the makers’ own claims. We have not used these bits ourselves. Where a listing fields disagree, we say so.
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What to Look For
| Feature | Why it matters |
|---|---|
| Size range | The smallest and largest step set the holes you can make |
| Step count | More steps give finer size choices |
| Coating or alloy | Titanium, black oxide and cobalt suit different jobs |
| Shank | A three flat or hex shank grips without slipping in the chuck |
| Markings | Etched size marks make it easy to see the step |
Specs at a Glance
| Bit | Range and count | Material or coating | Notes |
|---|---|---|---|
| IRONANT | 5 bits; 50 sizes | HSS with titanium coating | 3 flat shank; split point; aluminum case |
| NEIKO 10197A | 1/8 to 1-3/8 in; 5 bits, 50 sizes | Titanium HSS | Two flute; 3 flat shank |
| DEWALT DWA1790IR | 1/8 to 7/8 in; 3 bits, 31 sizes | Titanium nitride | 1/4 in hex shank; impact ready |
| Milwaukee #4 | 3/16 to 7/8 in; 12 steps | Black oxide | Dual flute; etched sizes |
| Milwaukee cobalt kit | 3 bits; sizes not listed | Cobalt | Dual flute; 3 flat shank |
| Milwaukee #5 | 1/4 to 1-3/8 in; 1 bit | Black oxide HSS | Dual flute; made in the USA per listing |
The 6 Best Step Drill Bits
1. IRONANT 5-Piece HSS Step Drill Bit Set, 50 Sizes
Five high speed steel step bits with a titanium aluminum nitride look finish, a 118 degree split point tip and a three flat shank, packed in an aluminum case. The maker says it is for plastic, aluminum, iron and sheet metal and states that it is not recommended for stainless steel or wood. The specification table shows a cutting diameter of 1 inch, so check the largest step if you need bigger holes.
Suits: general sheet metal and plastic. Strengths: 50 sizes and a case. Weaknesses: the maker excludes stainless steel. Skip it if you drill stainless.
View 5-Piece HSS Step Drill Bit Set for Metal, 50 Sizes, TiAlN Coated on Amazon
2. NEIKO 10197A Step Drill Bit Set, 5 Pc
Five titanium coated high speed steel bits covering 50 sizes from 1/8 to 1-3/8 inch, with two flutes and a three flat shank. The maker says it drills plastic, aluminum, copper, stainless steel and other sheet metal, and that it doubles as a hole expander. The table lists a 135 degree cutting angle.
Suits: a wide range of hole sizes. Strengths: a broad size range and a stated list of metals. Weaknesses: a five bit set is more than some need. Skip it if you need one hole size only.
3. DEWALT DWA1790IR Step Drill Bit Set, 3 Piece
Three bits with titanium nitride coating that together give 31 hole sizes from 1/8 to 7/8 inch: the included bits cover 1/8 to 1/2, 3/16 to 1/2 and 3/16 to 7/8 inch. They have a 1/4 inch hex shank, a two flute spiral and a split point, and are described as optimized for impact drivers. The table lists a cutting diameter of 6.5 mm, which is not consistent with the stated range.
Suits: impact driver users. Strengths: hex shank and laser engraved numbers. Weaknesses: tops out at 7/8 inch. Skip it if you need holes up to 1-3/8 inch.
4. Milwaukee #4 Step Drill Bit, 3/16 to 7/8 in
A single black oxide bit with 12 steps from 3/16 to 7/8 inch and a dual flute design the maker calls jam free. The maker also says black oxide gives up to four times longer life than uncoated step bits. Steps are etched with size markings and the bit is described for sheet metal and thin gauge steel. Model 48-89-9204.
Suits: thin metal. Strengths: clear markings and a stated life claim. Weaknesses: one bit only. Skip it if you want a set.
5. Milwaukee Cobalt Step Bit Kit, 3PC
A three piece kit with cobalt bits, an elongated dual flute, a rapid strike tip, laser engraving and three flat shanks. The listing has only five short bullets and does not give the step sizes, so check the model 48-89-9291 spec before buying. The weight shown is 1.3 pounds.
Suits: tougher metals. Strengths: cobalt construction and a three bit kit. Weaknesses: sizes are not stated on the page. Skip it if you need to know the range before ordering.
View Milwaukee Electric – Cobalt Step BIT KIT 3PC on Amazon
6. Milwaukee 48-89-9205 Step Bit #5, 1/4 to 1-3/8 in
A single black oxide high speed steel bit with a dual flute geometry that covers 1/4 to 1-3/8 inch. The listing says it has a 3/8 inch shank size and was manufactured in the United States. The table gives a cutting diameter of 1.07 inch, which does not match the title range.
Suits: larger holes in sheet metal. Strengths: the largest range of the three Milwaukee picks here. Weaknesses: conflicting diameter figures. Skip it if you need a small first size.
View Milwaukee 48-89-9205 Step Bit #5 1/4″ – 1-3/8″ on Amazon
Care and Setup
- Mark the hole with a center punch before you drill.
- Clamp thin sheet so it cannot spin with the bit.
- Use a cutting lubricant when drilling metal.
- Follow the maker’s speed advice and let the bit cut.
Mistakes to Avoid
- Skipping a pilot mark and letting the tip wander.
- Using a stainless steel job on a set the maker excludes.
- Drilling thick plate, which step bits are not meant for.
- Ignoring the shank type for your drill or impact driver.
Step Drill Bit FAQ
What are step drill bits used for?
They cut several hole sizes with one bit in thin material such as sheet metal, aluminum and plastic, and can enlarge an existing hole.
Which pick has the widest range?
The NEIKO set lists 1/8 to 1-3/8 inch across five bits. The Milwaukee #5 lists 1/4 to 1-3/8 inch in one bit.
The Short Version
For a 50 size set, the IRONANT or NEIKO. For impact driver use, the DEWALT. For a single 12 step bit, the Milwaukee #4. For cobalt, the Milwaukee kit. For the largest single bit, the Milwaukee #5.