Cone & Step Drill Bits
Cone and step drill bits open clean holes in sheet metal, plastic and thin materials without snagging, grabbing or swapping bits every five minutes on site.
When you're opening cable entries in trunking, drilling switchgear, or cleaning out thin steel without tearing it to bits, these are the ones to reach for. Good cone and step drill bits save time, leave a neater finish, and stop you wrecking panels with the wrong Drill Bits. If you're sorting out proper drill accessories for site work, match the step sizes to the holes you actually drill and buy for the material, not just the price.
What Are Cone and Step Drill Bits Used For?
- Drilling clean, stepped holes in sheet steel, stainless, aluminium and plastic is where these earn their keep, especially when you're fitting cable glands, conduit entries or panel fixings.
- Opening out existing holes in electrical boxes, trunking, cabinets and enclosures is far quicker with a step bit because it cuts in stages instead of snatching like a standard twist bit.
- Working on first fix and maintenance jobs, these bits help sparkies and fitters make tidy access holes in thin materials without burrs that chew up cables or leave a rough handover.
- Using one bit to cover several hole sizes cuts down the faff in the van and on the ladder, which matters when you need drilling bits for cordless drills that do more than one job.
- Finishing holes in plastics and laminates for site gear, vehicle interiors and plant panels is easier with cone and step drill bits because they track cleanly and are less likely to crack the material.
Choosing the Right Cone and Step Drill Bits
Sorting the right one is simple: match the bit to the hole range, the material and how often you will actually use it.
1. Hole Range First
If you only ever drill common gland and conduit sizes, buy a bit that covers those steps and no more. There is no point paying for a wide range if the top half of the bit never leaves the case.
2. Material Matters
If you are mostly in plastic trunking or light aluminium, a standard HSS bit will do the job. If you are regularly drilling stainless or tougher sheet steel, step up to better wear resistance or you will blunt it early and start burning holes instead of cutting them.
3. Single Bit or Set
If this is a daily-use bit for electrical or mechanical installs, a set makes sense because you cover more sizes and have a spare when one goes dull. If it is just for occasional snagging or odd access holes, one well-chosen bit is usually enough.
4. Shank and Drill Compatibility
If you are running them in drilling bits for cordless drills all day, make sure the shank grips properly in your chuck and the drill has enough control at lower speed. Too much speed and too little control is what ruins both the cut and the bit.
Who Uses These on Site?
- Sparkies use cone and step drill bits for opening gland holes in metal back boxes, consumer unit blanks, trunking and control panels where a rough hole is not good enough.
- Heating and ventilation fitters keep them handy for drilling thin ducting, brackets and plant casings, especially when they need one bit to step up sizes quickly without distorting the sheet.
- Maintenance teams and site engineers reach for them when adapting cabinets, kiosks and enclosures because they can enlarge an existing hole without dragging the whole panel about.
- Fabricators and installers use them on thin steel, aluminium and plastic when a holesaw is overkill and a standard twist bit would grab, chatter or leave too much cleaning up after.
The Basics: Understanding Cone and Step Drill Bits
These bits are built for thin materials where a normal twist bit can grab, tear or leave a mess. The shape is what makes them useful on site.
1. Step Cutting
A step drill bit cuts one size at a time as it goes deeper. That lets you stop exactly where you need, which is ideal for conduit, cable glands and panel work where one millimetre out can mean a loose fit.
2. Cone Shape for Opening Out
The tapered shape helps the bit start cleanly and enlarge holes without the violent snatch you get from some standard bits. That means less distortion in thin sheet and less clean-up afterwards.
3. Best in Thin Materials
These are not the bit for deep masonry or thick timber. They are at their best in sheet metal, plastics and thin plate where you want a neat, controlled hole with fewer tool changes.
Accessories to Keep Your Cone and Step Drill Bits Working
A few sensible add-ons make these bits cut cleaner, last longer and save you wrecking a good bit on a rushed job.
1. Cutting Fluid
Use it on steel and stainless or you will cook the edge and dull the bit long before it should be finished. It is a small thing, but it is the difference between a clean cut and a smoking, blued-up bit.
2. Centre Punch
A quick punch mark stops the bit wandering across smooth metal when you first start the hole. That saves scratched panels, off-centre entries and the usual site language that follows.
3. Deburring Tool
Even a tidy step bit can leave a sharp edge on some materials. A deburring tool cleans the hole properly so cables, glands and fixings sit right and nobody slices a hand on handover.
4. Spare Step Bit Set
If you use these for service work or first fix, keep a spare in the van. Once one bit dulls halfway through a day of panel drilling, you will wish you had not tried to stretch it.
Choose the Right Cone and Step Drill Bits for the Job
Use this quick guide to avoid buying the wrong bit for the work in front of you.
| Your Job | Category or Type | Key Features |
|---|---|---|
| Drilling cable gland holes in trunking and panels | Step drill bit | Common electrical hole sizes, clean staged cutting, reduced snagging in thin sheet |
| Opening out existing holes in metal enclosures | Cone drill bit | Tapered profile, smooth enlargement, better control on thin materials |
| Regular work in stainless or harder sheet steel | Higher wear resistance step bit | Built for tougher metals, longer edge life, less heat build-up |
| General maintenance jobs across mixed materials | Multi-size step bit set | Covers several hole sizes, fewer bit changes, useful for plastic and aluminium too |
| Quick site drilling with cordless kit | Step bit for cordless drills | Stable shank fit, works at controlled low speed, good for van and ladder work |
Common Buying and Usage Mistakes
- Buying the widest size range just because it looks useful often wastes money. If the bit does not cover the hole sizes you use most, or includes loads you never touch, it is the wrong bit for the van.
- Running step bits too fast is a classic mistake and it ruins them. Slow the drill down, use steady pressure and add cutting fluid on metal or you will blunt the edge and scorch the work.
- Using cone and step drill bits on thick material as if they were standard twist bits leads to slow cutting and poor results. They are meant for sheet metal, plastics and thin sections, not deep heavy drilling.
- Starting on smooth steel without a punch mark makes the bit skate off line. Mark the hole first or expect scratched panels and a hole that is not where it should be.
- Ignoring burrs after drilling causes problems later when glands, fixings or cables go in. Clean the edge properly and the finish will be safer and look like a proper trade job.
Cone Drill Bits vs Step Drill Bits vs Twist Drill Bits
Cone Drill Bits
Best for enlarging holes cleanly in thin materials and keeping control in sheet metal or plastic. They are handy for adjustment work, but they are less exact than a stepped profile when you need repeatable set hole sizes.
Step Drill Bits
These are the better choice when you need fixed hole sizes for glands, conduit or fittings. They cut progressively, leave a neater finish in thin material and stop you swapping between several standard bits.
Twist Drill Bits
A standard twist bit is still right for solid material, pilot holes and general drilling, but in sheet metal it can grab hard and leave a rough hole. Use them where they suit, not as a substitute for proper step drilling.
Which Should You Buy
If your work is mostly panels, trunking, enclosures and thin steel, buy cone and step drill bits first. If you are drilling brick and block, go to Masonry Drill Bits. For timber or metal pilots and general-purpose work, HSS Drill Bits still need a place in the box.
Maintenance and Care
Clean Off Swarf After Use
Wipe the bit down after drilling metal so swarf does not sit in the flutes or steps. Leaving sharp filings stuck on the bit is asking for rust, dull edges and cut hands next time you grab it.
Use Lubrication on Metal
A drop of cutting fluid keeps heat down and helps the bit stay sharp for longer. Dry drilling steel all day is one of the quickest ways to kill a decent bit.
Store Them Properly
Keep cone and step drill bits in their case or a dedicated organiser, not rolling about loose with fixings and other drill accessories. Knocked cutting edges do not stay sharp for long.
Watch for Dulling and Burning
If the bit starts squealing, burning or taking far too much pressure to cut, it is past its best. Replace it before it wrecks the workpiece and wastes more time than it is worth.
Keep Them for the Right Jobs
Do not abuse these on masonry, thick plate or jobs better suited to Holesaws & Accessories. Use the right bit for the material and your step bits will last a lot longer.
Why Shop for Cone and Step Drill Bits at ITS?
Whether you need a single replacement for site repairs or a full set of cone and step drill bits for regular panel and sheet work, we have the range ready. You will find trusted Power Tool Accessories for trade drilling, all stocked in our own warehouse and ready for next day delivery across the UK.
Cone and Step Drill Bits FAQs
What are cone and step drill bits used for?
They are mainly used for drilling and enlarging clean holes in sheet metal, plastic, trunking, enclosures and other thin materials. On site, they are ideal for cable glands, conduit entries, control panels and any job where a standard bit is likely to grab or leave a rough edge.
How do I choose the right cone and step drill bits?
Start with the hole sizes you actually need, then check the material you drill most often. If you are mainly working in thin steel or plastic, a good step bit covering your common sizes is the sensible buy. If you are often opening out existing holes, a cone profile can be the better shout.
Which cone and step drill bits are best for trade drilling?
The best ones for trade drilling are the bits that stay sharp, cut cleanly and cover the sizes you use every week, not just the cheapest set on the page. For regular site use, look for solid HSS construction, clear step markings and a size range that suits your usual electrical or mechanical work.
Can cone and step drill bits be used with cordless drills?
Yes, they work well with cordless drills as long as the drill has decent low-speed control and enough torque for the material. They are especially useful as drilling bits for cordless drills because one bit can cover several sizes, but you still need to keep speeds sensible to avoid burning the edge.
Can I buy cone and step drill bits online from ITS?
Yes, you can buy cone and step drill bits online from ITS, with the range in stock and ready for next day delivery. If you are also sorting the rest of your kit, it is worth checking the wider Drill Bits range at Drill Bits before you check out.
Will these replace holesaws for bigger holes?
Not always. For thin sheet and common entry sizes, yes, they are often faster and tidier. Once you need larger diameters or are working in thicker material, proper Holesaws & Accessories are usually the better option.
Are these any good for brick or block?
No, this is the wrong bit for masonry. Cone and step drill bits are for thin metal and plastic work. If you are drilling brick, block or concrete, use proper Masonry Drill Bits instead or you will blunt the bit and get nowhere fast.
Do I still need standard metal bits as well?
Yes. Step bits are brilliant for thin materials and set hole sizes, but they do not replace standard metal bits for pilot holes, thicker sections or general drilling. Keep a set of HSS Drill Bits in the kit for the jobs step bits are not meant to do.
