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A step bit is principally a sheet-metal and thin-stock tool: its labelled diameters make repeatable holes in electrical boxes, panels and thin steel without swapping twist drills. It is not a substitute for an annular cutter or a conventional drill for thick plate. Match the final diameter, number of steps, shank and material to the job, use cutting fluid where appropriate, clamp the work, and stop when the labelled step reaches the hole size. Titanium-nitride-coated high-speed steel is a practical general choice; cobalt is worth considering for tougher stainless work, while no step bit should be forced through stock thicker than its maker permits.
| # | Product | Price | Where to buy |
|---|---|---|---|
| 1 | IRWIN UNIBIT #1T Titanium Nitride Step Drill | $25–$40 | Amazon · eBay |
| 2 | IRWIN UNIBIT #3T Titanium Nitride Step Drill | $30–$50 | Amazon · eBay |
| 3 | IRWIN UNIBIT #4T Titanium Nitride Step Drill | $35–$60 | Amazon · eBay |
| 4 | IRWIN UNIBIT #1C Cobalt Step Drill | $50–$65 | Amazon · eBay |
| 5 | Milwaukee #4 Step Drill Bit 48-89-9130 | $35–$55 | Amazon |
| 6 | Milwaukee #9 Step Drill Bit 48-89-9209 | $55–$65 | Amazon · eBay |
| 7 | Milwaukee Shockwave Impact Duty Step Bit Set 48-89-9232 | $90–$130 | Amazon |
| 8 | Klein Tools Step Drill Bit 59001 | $35–$50 | Amazon |
| 9 | Diablo #4 Cobalt Step Drill Bit DHS4-S | $45–$70 | Amazon · eBay |
| 10 | DEWALT Titanium Step Drill Bit DWA1790IR | $20–$35 | Amazon · eBay |
The picks, in detail
IRWIN UNIBIT #1T Titanium Nitride Step Drill
A 13-hole, 1/8–1/2-inch titanium-nitride-coated bit with 1/32-inch increments for small conduit and panel holes.
- 1/8–1/2 in. range
- 13 labelled steps
- 1/4 in. shank
- fine 1/32-inch sizing
- single-bit option
- limited to 1/2 inch
IRWIN UNIBIT #3T Titanium Nitride Step Drill
A nine-step 1/4–3/4-inch bit with a 3/8-inch shank for larger holes in thin sheet metal.
- 1/4–3/4 in. range
- 9 steps
- 3/8 in. shank
- useful mid-size range
- clearly marked steps
- starts at 1/4 inch
IRWIN UNIBIT #4T Titanium Nitride Step Drill
A 12-step, 3/16–7/8-inch single bit for wide electrical-box and panel openings.
- 3/16–7/8 in. range
- 12 steps
- 3/8 in. shank
- broad single-bit range
- TiN coating
- not for thick plate
IRWIN UNIBIT #1C Cobalt Step Drill
A cobalt-alloy 13-hole bit spanning 1/8–1/2 inch in 1/32-inch steps, aimed at more demanding metal work than coated HSS.
- M35 cobalt alloy
- 1/8–1/2 in. range
- 13 steps
- fine increments
- cobalt construction
- higher cost than TiN HSS
Milwaukee #4 Step Drill Bit 48-89-9130
Milwaukee’s #4 black-oxide, dual-flute step bit covers 3/16–7/8 inch and uses a 3-flat Secure-Grip shank.
- 3/16–7/8 in. range
- dual flute
- 3-flat shank
- anti-slip shank
- laser-engraved marks
- single size range only
Milwaukee #9 Step Drill Bit 48-89-9209
A two-step 7/8–1-1/8-inch black-oxide bit for enlarging an already prepared thin-metal opening to a large final diameter.
- 7/8 and 1-1/8 in. steps
- dual flute
- 3-flat Secure-Grip shank
- large-hole capacity
- Rapid Strike tip
- only two diameters
Milwaukee Shockwave Impact Duty Step Bit Set 48-89-9232
A three-piece impact-rated set containing Milwaukee #1, #4 and #9 step-bit ranges rather than one universal bit.
- 3-piece set
- impact-rated hex shanks
- #1 #4 and #9 ranges
- covers small through large holes
- set keeps ranges distinct
- costlier than a single bit
Klein Tools Step Drill Bit 59001
A 13-step, 1/8–1/2-inch high-speed-steel bit with a 1/4-inch quick-change shank for thin electrical enclosures.
- 1/8–1/2 in. range
- 13 steps
- 1/4 in. quick-change shank
- compact driver-ready shank
- fine increments
- does not reach large knockout sizes
Diablo #4 Cobalt Step Drill Bit DHS4-S
A cobalt step bit sold for 3/16–7/8-inch holes in metal, with a 3-flat shank and step markings for controlled enlargement.
- 3/16–7/8 in. range
- cobalt construction
- 3-flat shank
- cobalt choice for hard metal
- wide 12-step range
- premium single-bit price
DEWALT Titanium Step Drill Bit DWA1790IR
A titanium-coated 1/8–1/2-inch, 13-step bit with a 1/4-inch impact-ready shank for smaller sheet-metal holes.
- 1/8–1/2 in. range
- 13 steps
- 1/4 in. impact-ready shank
- driver-compatible shank
- small-diameter coverage
- TiN coating can wear with misuse
Buying tips
- Use a punch or pilot only if the bit maker calls for it, clamp thin sheet firmly, and run at a controlled speed with suitable cutting fluid.
- A step-bit diameter is the finished hole diameter; read the laser mark before advancing to the next shoulder.
- For thick steel, structural members or holes that must be highly accurate, choose the correct twist drill, annular cutter or hole saw instead of forcing a step bit.
As an Amazon Associate and eBay Partner, toptenpick.com earns from qualifying purchases. Prices and availability are subject to change.