Wood Forstner Drill Bits Set

Product Overview

A Forstner bit set is not a substitute for a general-purpose bit set; it is the set you buy on purpose, usually because a job needs a recess rather than a through-hole. Cabinet making is the classic case: the moment you fit a concealed hinge, a drawer runner or a magnet catch, you need a pocket with a flat floor and an exact depth, and a twist bit or a spade bit cannot make one.

Three features define the tool. The rim cutting teeth lie in one plane and do the cutting, the sizing and the guiding, which is what produces a flat bottom and a true diameter. The centre point marks the position and gives the bit a pivot at the start — but it does not feed the bit forward, so unlike an auger, a Forstner relies on your hand for feed. The chip slots between the rim and the shank are the only way the swarf can leave the hole, which is why chip clearance, not horsepower, is the usual limit on how fast a Forstner cuts.

This set is supplied in the diameters that cover furniture and joinery work, headed by the 35 mm bit that fits the standard European concealed hinge cup. The cutting teeth are brazed tungsten carbide, which matters more on a Forstner than on almost any other bit: the materials most often bored with one — MDF, particleboard, plywood and laminate — are full of resin and mineral filler that is abrasive, and an HSS edge dulls against them quickly. The bodies are alloy steel with a blue powder-coat finish; the bit photographed for this page is dimensioned at 25 mm diameter and 85 mm overall length.

A note on the words. The original product description calls the job “flat bottoms and pocket holes”. A Forstner bit genuinely makes the flat-bottomed pocket — a recess. It does not make the angled pilot-and-countersink that goes with a pocket-screw jig; that is a different bit and a different operation. This page uses “pocket” strictly to mean a flat-bottomed recess.

How a Forstner Bit Cuts: Rim-Guided, Not Point-Guided

Understanding why this bit behaves the way it does comes down to one question: what does the bit use to find its position and hold its line? Every wood bit answers that question differently, and the answer decides everything about how it must be used.

Three bits, three ways of being guided

A twist bit is guided by its flutes bearing on the wall of the hole and, in a brad-point version, by a long spike. It works in thin material and in metal, and it wanders in thick timber. An auger bit is guided by a threaded lead screw that bites the timber and drags the bit forward at a rate set by the thread — which makes it fast and self-feeding, and leaves a screw point’s cone at the bottom of a blind hole. A Forstner bit is guided by its rim: the toothed circumference that cuts the wall of the hole. It has no lead screw, so it does not pull itself in; it has only a short centre point, which marks the position and then does nothing.

Two consequences follow, and they are the whole character of the tool:

• The bottom is flat. Nothing protrudes through the plane of the cutting teeth, so a blind hole finishes with a flat floor plus a shallow centre dimple. That is what makes the bit usable for a hinge cup, an inlay or a T-nut seat.
• You feed it, not the bit. With the self-feeding removed, the feed rate is entirely under your hand. That is a benefit — you can creep up on a 12.5 mm depth stop — and a responsibility, because pushing instead of cutting is how a Forstner overheats.

Why the rim being the guide also means the rim must be square

A rim-guided cutter has a hard requirement: it only cuts a true circle if it enters on its own axis. Tilt the bit and the rim touches on one side first, cutting a crescent, and the hole comes out oval, undersized on one side and too large on the other. The hardware then rocks in a hole that is not round. This is why the same operation that is trivially easy on a drill press — boring a 35 mm cup — is genuinely hard with a hand drill, and why the professional answer is a drilling jig or guide block rather than a steadier hand.

The centre point: small, and not a decoration

The point does two jobs. It gives you something to place on your awl mark so the bit does not walk across a finished face before it bites, and it holds the bit on that mark for the first few degrees while the rim establishes the wall. It does not hold the bit square — that is your setup — and it does not pull the bit down. A flat or damaged point is the usual reason a Forstner starts off-centre, and it is not worth tolerating: on hardware work an off-centre cup cannot be adjusted back.

What the Missing Lead Screw Buys You

Remove the screw point from a bit and, paradoxically, you gain freedom. Because the Forstner does not need a lead screw to be holding material in order to advance, it can cut in situations where a self-feeding bit would lose its feed and lurch — and because its rim is a complete circle that cuts all the way round, it can cut a shape that is not entirely surrounded by wood.

1. A flat-bottomed hole to an exact depth

The core capability, and the reason the bit exists. Bore to the depth stop, withdraw, and the pocket is flat. For a hinge cup that means the cup sits flush; for a T-nut or threaded insert it means the hardware seats on a flat floor instead of wobbling on a cone.

2. Overlapping holes — a pocket made from a row of bores

Bore a series of overlapping circles and you have removed the bulk of a slot or a mortise with clean walls, ready to square the ends with a chisel. This is the standard way to rough out a mortise for a lock body, a hinge leaf or a fastener plate without a mortiser. The rim of each hole cuts a full clean arc, so the sides are far tidier than what a spade bit would leave. Use a bit slightly narrower than the mortise is wide, and step across in fractions of a diameter.

3. A half hole on the edge of a board

Clamp a scrap behind the work so the rim has something to cut into, position the bit so half of it hangs over the edge, and bore: you get a clean half-circle in the edge of the board. That is how an edge bore is made for a dowel at the edge of a panel, or a recess on the edge of a rail. A spade or twist bit will walk off the edge; a rim-guided bit cannot, because the part of the rim that is in the wood establishes the cut.

4. An angled hole

Because the rim cuts all the way round regardless of how it meets the surface, an angled hole comes out round rather than torn — splayed dowels in a chair leg, for example, or a recess in a sloping surface. The rule is only that the bit must enter along its own axis: it will cut an angled hole relative to the workpiece, but it will not be steered to that angle for you. Mark the angle, present the bit square to the axis you want, and hold it there.

5. A pocket for hardware, in one pass

Because the diameter is fixed by the rim, a Forstner bores a pocket that matches the hardware exactly — cup, magnet, insert, flush-mount plate or badge. For a run of identical doors, that repeatability is worth more than the cutting speed, and it is the reason a hinge-cup jig plus a 35 mm Forstner is faster in practice than any freehand method.

The honest limit: none of this makes the Forstner a fast bit. It removes material at the bottom of a hole, not along a deep channel, and it is the slowest of the wood bits in deep timber. For deep structural holes you want an auger bit set; for a quick rough through-hole a flat (spade) bit set is faster. The Forstner is the bit you choose when the finish matters more than the clock.

Rim Types in the Forstner Family

“Forstner” describes a geometry — rim-guided, flat-bottomed — not a single cutting edge. Within the family the rim is made in three forms, and the form changes the finish, the chip clearance and the diameter the bit is sensible in. Knowing which you are holding explains most of the difference in how two Forstner bits of the same size behave.

There is a second, independent choice: the cutter material. A Forstner edge is either high-speed steel or a brazed tungsten carbide tip. On clean softwood and hardwood the two behave similarly, but on MDF, particleboard, plywood and laminate — the boards furniture is actually made of — carbide holds its edge far longer, because those materials carry resin and mineral filler that is abrasive. The bits shown here are carbide tipped. For the full material comparison, see the single-bit page, Wood Forstner Drill Bits.

Which Diameter for Which Job

In a Forstner set the diameter is not a clearance choice, it is a fit choice: the hole has to match the hardware or the dowel. These are the jobs that account for most Forstner use, and the sizes that go with them.

Two rules of thumb make the choice reliable. First, match the hardware, not the nearest round number: a cup hinge needs 35 mm because the cup is 35 mm, and a dowel needs the dowel’s own diameter so the joint closes. Second, bore the smallest diameter that will do the job: a smaller bit removes less material, generates less heat, is easier to keep square and puts far less torque through your wrist. Where the hardware allows, pick the small bit and take two passes rather than one big one.

Full Specifications

Prices run roughly US$5–40 per set depending on set size, diameters, cutter material and packaging. Tell us the board materials you bore and the hardware you fit and we will quote the set that matches, rather than the one that happens to be nearest.

Making a Flat-Bottomed Recess: Methods Compared

A flat-bottomed recess is a specific deliverable, and several tools will claim it. They are not interchangeable, and the differences show up the moment the recess has to match hardware or sit on a visible face. This table compares them on the qualities that decide the choice.

The working rule: for a round recess with a flat floor — which is most hardware — the Forstner is the fastest thing that will do the job properly. Reach for the router when the recess is not round or when you are making hundreds of identical ones; the template pays for itself over a run. Never reach for a spade or brad-point bit when the bottom is going to be seen or the hardware is going to sit on it, because the point leaves a cone and the hardware will not seat.

The 35 mm Hinge Cup and Furniture Hardware

The 35 mm bit is the reason most people buy a Forstner set, and the operation is unforgiving enough to deserve its own numbers. Get it right and the door hangs and adjusts; get it wrong and the door is scrap, because an off-centre or over-deep cup cannot be corrected.

The standard dimensions

The two errors that ruin doors

Too deep. Break through the front face and the door is finished. This is the reason a 12.5 mm bore in a 16 mm door is a close call and a depth stop is not negotiable. If you have gone a fraction deep, cut a thin disc of veneer or card to fit the bottom of the cup; glue it in and the hinge sits flush again. If you have gone through, the door has to be replaced or re-faced.

Off centre. The centre point marks the position, but the bit still has to enter square. Tilt it and the cup recess comes out oval, and an oval cup means a hinge that rocks and a door that will not adjust true. Mark with an awl, clamp the door, and use a jig or a guide block rather than relying on a steady hand. A repeatable jig is also faster over a run of doors, because the setup cost is paid once.

Beyond the cup: the other hardware jobs

The same logic covers the rest of the cabinet’s ironmongery. Magnet catches and flush-mount plates want a shallow pocket at an exact depth so the plate sits flush with the surface. T-nuts and threaded inserts need a flat seat, because on a conical bottom they tilt and the fixing cannot pull square. Drawer runners, shelf pins and bench dogs all want a bore of a specific diameter with a clean edge. And in joinery, dowel and loose-tenon holes want a flat bottom so the dowel seats against the base and the joint closes hard, instead of bottoming out on a screw point’s cone and leaving a gap.

Drill Press or Hand Drill?

This is the decision that determines whether a Forstner job goes well, and the honest answer is that the tool wants a drill press and will tolerate a hand drill only within limits.

Why the bit wants a drill press

The rim is the guide, so the bit’s accuracy is almost entirely a function of how squarely it enters and how well it is held on axis while it cuts. A drill press gives a fixed 90-degree axis, a table that holds the work, and a depth stop you can repeat exactly — the three things a Forstner needs. On cabinet work that is decisive: identical cups on a run of doors come from a fixed setup, not from a steady arm.

What a hand drill can and cannot do

General practice in the trade is that Forstner bits up to about 19 mm (3/4 inch) can be used in a hand drill with care, and larger ones should not be. The reason is not only accuracy. A large Forstner takes a deep bite, and if it hangs on a knot, a glue line or a change of grain, it will spin the drill — or spin the workpiece if the workpiece is lighter than the drill. A 35 mm cup bit in a hand drill is a real hazard, and the professional answer is not a firmer grip but a drilling jig or guide block. With a guide to hold the axis and clamps to hold the door, hand boring a hinge cup is repeatable. Without them it is luck.

The setup that works

• Clamp the work. Never hold a piece being bored with a Forstner by hand — if it catches, the piece becomes a projectile. Add a sacrificial backer underneath for through-holes and for edge work.
• Mark with an awl. A dimple locates the point and stops it skating across a laminate or a finished face.
• Set the depth stop, and check it against a scrap. Bore a test hole in an offcut of the same thickness before you touch the real door.
• Prepare for the breakthrough. On a through-hole, ease off as the point exits and let the bit coast into the backer rather than driving it through.
• Two hands and the auxiliary handle on any diameter where the bit could grab, so the torque has somewhere to go.

Speed, Feed and the Peck Cycle

Speed: governed by the rim, not the spindle

The number that matters is the speed at which the rim travels, and the rim is further from the centre on a big bit, so it travels faster at the same rpm. That is why every Forstner speed chart in existence says the same thing in different numbers: small bits fast, big bits slow. Makers publish figures that differ quite widely — some are conservative hobbyist numbers, some are production numbers — so use the table as a starting band and let the shavings tell you where to land inside it.

The invariant that survives every chart is simple: double the diameter and you should halve the rpm, because that keeps the rim speed roughly constant. If you cannot remember a single figure, remember that one.

Feed: light, steady, and never as a substitute for sharpness

A Forstner wants a light, even feed and no more. Two things go wrong when you push. The bit cannot clear its chips faster than it makes them, so the rim begins to rub rather than cut; and the friction converts to heat, which softens the edge and burnishes the wall. Because there is no self-feeding screw to limit the rate, the temptation to lean on the drill is stronger with a Forstner than with any other bit — and it is always the wrong answer. If the bit needs force to cut, it is dull, too fast, or full of chips; adding pressure only makes all three worse.

The peck cycle: the single habit that saves Forstner bits

A Forstner cuts a full circle, and its chips have only the slots between the rim and the body to escape through. At even shallow depths they accumulate, and once the rim is sitting on a bed of its own swarf it stops cutting and starts rubbing. The fix is to bore a short distance, withdraw the bit completely, let the slots empty, then go back in — about every 5 to 10 mm, and more often in resinous softwood or MDF, where the dust is fine and packs tightly. Two further points follow from the same physics:

• Clear the hole between passes when mortising. If you are boring a row of overlapping holes, empty each hole before starting the next, so the new cut is not made into a pile of debris.
• Never poke chips out with the cutting edge. Carbide is brittle; levering swarf out of the slot with the rim chips the teeth. Use a brush or a blast of air.

Materials, Janka and Abrasive Boards

A Forstner bit meets a wider range of “wood” than a framing bit does, and the range matters, because hardness changes the feed and abrasiveness changes the edge life.

Hardness: the Janka number tells you what to expect

The Janka scale measures the force needed to embed a steel ball in the wood, in lbf. It maps well onto how a Forstner behaves, because a harder wood both resists the cut and holds the heat. Some anchors: balsa around 100, pine and other softwoods roughly 380–600, poplar about 540, cherry about 950, walnut about 1,010, oak about 1,360, hard maple about 1,450, hickory about 1,820, and something like ipe above 3,000.

Abrasiveness: why furniture boards are the real test

The materials a cabinetmaker bores most often are not solid timber at all. MDF, particleboard and chipboard are wood fibre or chips bonded with resin, and many boards carry mineral fillers and hard glues; plywood has glue lines running through it; laminate and melamine have a hard, brittle surface layer. All of it is abrasive out of proportion to its softness. An HSS edge dulls quickly against these boards even though they cut easily, and a dull Forstner burnishes a laminate face rather than slicing it. That is the practical argument for a carbide-tipped bit, and it is why the bits shown here are brazed TC.

Two related cautions. End grain is much harder to bore cleanly than side grain, and it is where a sawtooth rim earns its keep; the tool makers’ guidance for Forstner bits is generally side-grain boring, with sawtooth cutters recommended for end grain. And reclaimed or painted timber may hide nails, staples and old fixings that will chip a rim in one revolution — probe and inspect before the bit goes in.

Not for: this is a woodworking bit. It is not for masonry, brick, block or concrete — that is the HSS twist drill bit set‘s world in metal and the diamond core bits for stone; and it is not for metal or metal studs. Running this set on the wrong material is the fastest way to destroy it.

Sharpening a Carbide-Tipped Forstner Bit

A Forstner has three working surfaces — the rim teeth, the outside diameter, and the centre point — and only one of them is meant to be touched. Getting that right is the difference between a bit that lasts for years of cabinet work and one that is thrown away at the first dull edge.

What to sharpen and what to leave alone

Use a diamond, never a bench grinder

On a brazed carbide tip the rule is absolute: hone with diamond, by hand. A bench grinder puts enough heat into the tooth to micro-crack the carbide and to soften the braze that holds it to the steel — and a tip that has been overheated will come off in service rather than cutting. Carbide is also brittle in a way steel is not, so treat the head as glass: do not drop the bit on a concrete floor, do not use it as a lever, and do not bang it out of the chuck.

How a Forstner retires

Storage

Keep the set in its case with each bit in its own slot. Carbide teeth chip against anything hard, and a handful of loose Forstner bits in a toolbox will chip each other’s rims within a week — and a chipped rim is a scrapped bit. Keep the bits dry; a light wipe of oil on the shank and body after use stops rust in a damp workshop, because a rusted shank drags in the chuck and a rusted body drags in the hole.

Safety

Boring a recess looks like the gentlest job in the workshop. It is also the one where a bit hangs, the torque has nowhere to go, and either the work or the drill starts to spin. The hazards are specific, and so are the defences.

• Eye protection, always. A Forstner throws fine, hot dust and small chips at face height.
• No loose gloves, sleeves or jewellery near the drill. A rotating shank or rim will take a glove and the glove will take a finger.
• Tie back long hair for the same reason.
• Dust extraction and a respirator. MDF and particleboard dust is fine and persistent and many boards carry formaldehyde-based binders; a Forstner makes a lot of it. Extract at source, and wear a suitable mask in an enclosed space.
• Two hands and the auxiliary handle on any diameter large enough to grab, so the reaction torque has somewhere controlled to go.
• Let the bit stop before you put the drill down. A rotating Forstner laid on a bench will walk, and it will find your hand.
• Check the timber first. Nails, staples and old fixings chip a carbide rim in a single revolution and put the torque into your wrist. Probe and inspect reclaimed or painted stock.

Applications

Cabinet making and furniture hardware

The core application. The 35 mm cup recess for European concealed hinges, magnet catches, flush-mount plates, drawer-runner and shelf-pin bores, and seats for T-nuts and threaded inserts. The requirement in every case is a flat floor and an exact diameter, which is exactly what a rim-guided bit delivers.

Dowel and loose-tenon joinery

Dowel holes, loose-tenon mortises and bed-bolt recesses. A flat bottom is not cosmetic here: a dowel that bottoms out on a screw point’s cone holds the joint open by the depth of the cone. With a flat-bottomed hole the dowel seats on the base, the shoulders of the joint close hard, and the glue line is the only gap left.

Mortising, before the chisel

Overlapping Forstner holes remove the bulk of a mortise quickly and with clean sides, leaving only the corners to be squared with a chisel. This is the standard bench method for a lock-body mortise, a hinge leaf or a fastener plate, and it is far tidier than what a spade bit leaves.

Inlay, veneer and decorative work

Recesses for inlay, veneer patches, marquetry inserts and decorative dots. The exact-depth flat bottom is what makes a patch sit flush, and the sawtooth rim is what keeps the entry edge clean on a visible face.

Edge, overlap and angled holes

Half holes on the edge of a panel, elongated pockets made from a row of overlapping bores, and angled holes such as the splayed dowels in a chair leg. These are the jobs that no other wood bit can do at all, and they are the clearest argument for keeping a Forstner set alongside the augers and spades.

Jigs, fixtures and workshop furniture

Flat-bottomed seats for bench dogs, holdfast collars, threaded inserts and T-nuts, and repeatable recesses in shop-made jigs and templates. A rim-guided bit marks its own diameter and depth every time, which is what a jig needs.

Not the right tool: this set bores wood and wood-based boards and nothing else. It cannot be used in masonry, brick, block or concrete — for those, see the HSS twist drill bit set for metal or the diamond core drills for stone. For deep structural holes in framing, use the wood auger bit set; for a fast rough through-hole, a flat (spade) bit; for a large circle for a pipe or a lock, a hole saw. For countersinking a screw head, the dedicated wood countersink drill bits are the correct tool rather than a Forstner.

How to Bore a Flat-Bottom Hole

1. Confirm the job wants a Forstner. If the hole has to finish flat, or has to match a piece of hardware, or has to run off the edge of a board, this is the right bit. If it is a deep structural hole, switch to the auger set before you start.
2. Choose the diameter from the hardware, not the drill index. 35 mm for a standard European hinge cup; the dowel’s own diameter for a dowel joint; the insert’s own diameter for a threaded insert.
3. Inspect the material. Check reclaimed and painted stock for nails, staples and old fixings, and confirm what board you are boring — MDF and laminate need a slower speed and a sharper edge than pine.
4. Mark the centre with an awl. A dimple locates the point and stops it skating across a laminate or a finished face. Pencil is not enough on a smooth board.
5. Clamp the work, and add a backer. Clamp the workpiece so it cannot move, and clamp a sacrificial board hard against the exit face if the hole is going through or if you are boring an edge hole.
6. Fit the bit properly. Seat the shank fully in the chuck or the quick-change holder and confirm it is locked. A partially engaged shank is what rounds off a holder.
7. Set the depth stop, and prove it on a scrap. Bore a test hole in an offcut of the same thickness and measure it. On a 12.5 mm cup in a 16 mm door there is no room for error, so this step is the one that saves the door.
8. Set the speed for the diameter. Small and fast, large and slow — roughly 500 to 1,000 rpm for a 35 mm cup, less in hardwood and MDF.
9. Enter square, and let the rim cut. Present the bit perpendicular to the surface, start the drill, and lower it lightly until the rim is fully engaged. The rim is the guide, so the entry angle is everything.
10. Peck to clear the rim. Every 5 to 10 mm, withdraw the bit completely and let the chip slots empty. In MDF and resinous softwood, do it more often.
11. Do not steer with the drill. If the hole is drifting, stop and restart rather than levering the drill sideways, which binds the shank and burns the edge.
12. Stop at the stop and withdraw. Let the bit come to rest at the depth you set, withdraw at running speed, and do not re-enter to tidy up — a second pass into a clean hole only adds heat.
13. Test-fit, then maintain. Drop the hardware in and check for rocking; shim a slightly deep cup with a thin disc of veneer or card. Brush the chips out of the slots, wipe the body, and put the bit back in its own slot in the case so the carbide rim is protected.

Frequently Asked Questions

OEM & Wholesale

GUSHI has manufactured and exported tools from Huzhou, Zhejiang since 2004, and supplies wood boring and drilling accessories to tool distributors, DIY and hardware retail programmes, and branded ranges in more than 20 countries. We are one of the 23 Chinese companies that won the diamond blade anti-dumping case for the USA market, with production capacity of 100,000 sets per month.

What we can build to your specification:

• Set contents from 3 to 16 pieces, with the mix of diameters chosen for your market
• Metric and imperial sizes, including the 35 mm cup bit and the intermediate diameters your market asks for
• Carbide-tipped or HSS cutters, sawtooth, continuous or staggered rim forms
• Round, three-face, hex and reduced shanks, and shank lengths to suit your machines
• Body colour, powder-coat finish and laser marking to your specification
• Storage case, roll, blister card, printed sleeve, colour box and carton — plus your brand and artwork