When you need to drill a hole larger than 10mm or so in wood, the choice between a Forstner bit and a hole saw makes a real difference to both the finish and your workflow. This guide cuts through the jargon and tells you which tool actually does the job better for the work you’re doing.
Quick Comparison: Forstner Bit vs Hole Saw
| Feature | Forstner Bit | Hole Saw |
|---|---|---|
| Hole bottom | Flat, clean, smooth | Rough, with centre pilot hole |
| Diameter range | 10–50mm (some up to 80mm) | 20–150mm+ available |
| Speed | Slower, more control | Fast, high volume |
| Tearout | Minimal, very clean edges | Can splinter, rougher exit |
| Best for | Hinge recesses, dowel holes, visible work | Pipe runs, cable holes, door locks |
| Setup | Into round shank chuck, press or hand drill | Needs separate arbour, pilot drill included |
| Cost | £4–8 per bit | £3–6 per bit, but need arbour (£5–15) |
What Forstner Bits Actually Do
A Forstner bit has a flat tip with a sharp cutting edge around the circumference and a centre pin that locates the hole. The design lets you drill holes with a completely flat bottom — no conical point like you get with a standard twist drill. That flat bottom is what makes Forstner bits indispensable for cabinet work and joinery.
Forstner Bit Advantages
The flat-bottom hole is the key. If you’re recessing hardware (hinges, barrel bolts, flush-mount cup hinges), you need that flat surface so the component sits dead flat. The hole is also clean and accurate — the cutting edge is well-defined and doesn’t wander like a twist drill can.
You can also drill overlapping holes with Forstner bits. The centre pin can start in open space rather than needing to begin on the surface. This is useful for large pocket holes or when you’re enlarging an existing hole. The bit won’t jump or grab the way a hole saw might.
Forstner bits typically work best at lower speeds (500–1500 rpm for hardwood, 1500–3000 rpm for softwood) in a drill press or a handheld drill with care. The cutting edge is relatively delicate compared to a hole saw, so they benefit from steady, controlled feeding.
Forstner Bit Limitations
Size is the main limitation. Most Forstner bits stop at 50mm diameter. Some brands make larger versions (up to 80mm), but they become expensive and require real drill press stability. Anything larger than 50mm, and you’re really looking at a hole saw.
Forstner bits are designed for wood. You can use them in plywood and MDF, but they’re not great in metals or masonry. They’ll work briefly in soft aluminium, but the cutting edges dull quickly on anything harder.
What Hole Saws Actually Do
A hole saw is a cylindrical saw blade with teeth around the edge. It cuts a ring rather than a solid bit, so the work piece comes out as a plug. Hole saws come in two main types: bi-metal (steel body with hardened teeth) and carbide-tipped (for harder materials).
Hole Saw Advantages
Speed is the big win. A hole saw makes light work of large-diameter holes quickly. They’re also available in much larger sizes — you can get hole saws from 20mm all the way up to 150mm or beyond. For plumbing runs, cable holes, or door lock cylinders, a hole saw is the practical choice.
Hole saws work in more materials than Forstner bits. Bi-metal hole saws handle wood, plastic, and soft metals. Carbide-tipped or diamond versions work in tile and masonry (more on that below). You’re not limited to wood-only work.
The cost per bit is often lower, though you do need an arbour (the mandrel that holds the hole saw onto your drill chuck). One arbour works with all the different diameter saws, so it’s a one-time purchase of £5–15.
Hole Saw Limitations
The hole bottom is rough. There’s always a centre pilot drill hole left behind, and the ring of the saw blade leaves a ragged edge that needs clearing out. If the hole is visible (like a cup hinge recess), you’ll see the roughness.
Hole saws can walk and grab, especially when they break through the back of the workpiece. You need a steady hand and preferably a drill press if you want accuracy. The plug (the waste ring) can jam inside the saw and snap it or bind up your drill.
They also generate a lot of heat. Clearing the plug regularly and letting the saw cool is essential, especially on harder woods or metals.
Forstner Bits for Cabinet and Joinery Work
If you’re fitting hinges, barrel bolts, flush-mount cup hinges, or dowels, Forstner bits are the right tool. The flat bottom means the hardware sits flush and secure. The clean edge means no sanding afterward in most cases.
Common sizes for cabinetry: 25mm for cup hinges, 32mm for larger hinges, and 16–20mm for dowel holes. A good cabinet-maker’s set includes bits from 10mm to 50mm in 2mm increments.
Buy Forstner bit set on Amazon
Hole Saws for Plumbing, Electrics, and Large Holes
For running 20mm pipes, 16mm conduit, or drilling door lock cylinders, hole saws are faster and more practical. The rough finish doesn’t matter because the holes are hidden inside walls or the workpiece.
Bi-metal hole saws are the workhorse. They’re tougher than Forstner bits and handle repeated use without dulling as quickly. A set of 9–15 saws (stepping from 20mm to 100mm) costs £15–25 and pays for itself on the first job.
Buy bi-metal hole saw set on Amazon
Diamond Hole Saws for Tiles and Glass
If you’re fitting pipes or cables through ceramic tiles, stone, or glass, standard hole saws won’t work. Diamond hole saws have diamond-coated edges that grind rather than cut. They’re slower but they don’t break or chip the material.
Diamond saws need water cooling (you can use a spray bottle or a wet sponge pad). Keep the bit wet and work at a slow speed (200–500 rpm). They’re expensive (£8–15 each) but essential for tile work and worth the investment if you do regular installations.
Buy diamond hole saw on Amazon
TCT Hole Saws for Hard Materials
Tungsten carbide tipped (TCT) hole saws are stronger than bi-metal and handle harder woods, cast iron, and some masonry. They cost more (£5–10 each) but last longer on tough materials.
TCT saws work best at moderate speeds (500–1000 rpm). Too fast and you overheat the carbide; too slow and you’ll bind up. If you’re regularly drilling cast iron or tropical hardwoods, TCT is worth the extra cost.
Arbour and Mandrel Compatibility
Most hole saws need a separate arbour (also called a mandrel) to fit into your drill chuck. The arbour is a shaft with a tapered or straight connection for the hole saw. Check that your saws match your arbour — there are two main types:
- SDS Plus arbour — for SDS drills only
- 1/2″ or 3/8″ straight arbour — for standard drill chucks
Most DIY and trade hole saw sets come with a standard straight arbour that fits any regular drill chuck. SDS Plus arbours are specialist items for hammer drill work.
Practical Decision Tree
Asking yourself these questions will tell you which tool to grab:
- Is the hole visible? Yes → Forstner bit. No → Hole saw.
- Bigger than 50mm? Yes → Hole saw. No → Either, depending on finish.
- In wood, plastic, or metal? Plastic/metal → Hole saw (bi-metal or TCT). Wood only → Forstner for clean work, hole saw for speed.
- Need a flat bottom? Yes → Forstner bit. No → Hole saw.
- Under time pressure? Yes → Hole saw. No → Forstner bit for better finish.
Watch: Video Guide
Frequently Asked Questions
Can You Use a Forstner Bit in a Cordless Drill?
Yes, but carefully. Modern cordless drills are powerful enough, but Forstner bits work best at lower speeds (1000–1500 rpm) and need steady pressure. A cordless combi drill with variable speed is better than a high-speed one. Impact drivers aren’t suitable — they’ll break the bit.
What’s the Difference Between Forstner Bits and Spade Bits?
Spade bits (also called paddle bits) have a wide flat blade with a centre point. They’re cheaper, tougher, and faster than Forstner bits but leave a rougher hole. Use spade bits for rough construction work; use Forstner bits for visible cabinet work.
Can You Use a Hole Saw in Hardwood?
Yes. Hardwoods are actually easier than softwoods for hole saws because they’re denser and the plugs come out cleanly. Just go steady on the pressure and clear the plug frequently to stop it jamming.
Do Forstner Bits Work in Plywood?
Yes, but watch for tearout on the exit side. The veneers can splinter. Back the workpiece with a scrap or use a backer board. Hole saws work better in plywood if the finish doesn’t matter.
What Speed Should You Use?
Forstner bits: 500–1500 rpm depending on hardness. Hole saws: 300–1000 rpm (slower for larger diameters and harder materials). Faster speed = faster feed but more heat and higher risk of binding. When in doubt, go slower.
How Do You Stop a Hole Saw From Jamming?
Stop regularly and clear the plug by reverse-spinning the drill and tapping the saw against the workpiece. Don’t let it build up inside the saw. If it jams, release the trigger and reverse immediately — don’t force it.
