Forstner drill: purpose, design, features

Benjamin Forstner patented his cylindrical drill for wood treatment in 1874.Since there are many varieties of this instrument.Some samples are only remotely resemble the Forstner drill bit, but they all operate on the principle of it.Use three types of cutting surface: sets the direction of the central island, the rim contour cuts the hole diameter, paired inner edge thickness of the material selected for the plane as rotating planes.Forstner drill


Forstner drill developed for breaching non-through hole with a flat bottom in soft and hard wood.At present, it is also used to work with MDF and chipboard, fiberboard and their modifications.

Deaf recess with a flat bottom often drilled for mounting of various furniture hardware (hinges, locks, eccentric and threaded couplers).In the production of material saving, using the minimum allowable thickness and through holes for furniture is not practiced.

need enough depth holes for mounting hardware and smooth and neat edges.Forstner drill bit for wood for

ms a perfect recess with a flat bottom.Thus before the drill can remain outwardly only 1-2 mm.Conventional drill screw having a conically sharpened, can not provide a plane and a pen-bits - the cleanliness and accuracy of the side surfaces.


working part has two main cutting edges and short centering tip.Drill according profile resembles beech Z rounded upper and lower part (specularly reflected letter S).On the bridge is elected the cutting edge, and along the rim - Trimming that after the formation of the well performs the role of stopper, holding the tool in diameter.

chips thrown up, which eliminates jamming of the drill.Incisions are made along the rim grinding machine.Elective edge can be corrected manually.To do this, use a file with a small notch or diamond-coated.Forstner drill bit for wood

The material is mainly used high-speed steel.It is well withstand moderate heating of the working area.Some manufacturers make an additional tool or sputtering titanium carbide-tipped.Often working edges cut teeth.This reduces overheating and increases the drilling rate with negligible loss of surface finish.

You can work with a standard drill chuck.For example, the 15-26 mm Forstner drill bit has a shank of 8 mm, and the tool with a large (28-60 mm) diameter working area - 10 mm.


For exact location of the drill is used at the beginning of the centering tip.Its target is placed in situ and pressed into the material to a uniform circular plane of tangency.At low speeds begin drilling.Drills are designed for operating speeds in the range of 800-1800 rpm.

The larger the diameter of the working area, the slower the cutting speed should be.This mode must be followed to avoid overheating of working edges.At higher speeds a high probability of relapse drill.

For safety and comfort, as well as in the case of critical parts useful Forstner drill bit with limiter.It is time to stop the tool and provide the necessary depth of the wells.

If you want to drill a hole in the thin material, when there is risk centering tip out, you can use two Forstner drill bit of the same diameter.Begin using conventional tools, they form the initial diameter.Forstner drill 15

The second drill grind centering tip.Complete deepening them already.The drill is held in the hole on the side planes of failure and there is no danger of leaving it outside.You can leave the minimum allowable wall.


Forstner drill (pictured above) in comparison with other designs has two important advantages: surface finish, and the fact that it keeps well a given direction.This works even across the opening, or when their diameters are outside the edge of the workpiece.

cut quality is achieved sidewalls undercut circumferential fibers before their touches the main cutting edge.This prevents chips and scratches to the material being processed outside diameter.

second advantage is provided in that direction holds no centering point and the side cutting edge of the ring and the entire cylindrical surface of the working plane.After the start of the sample material is held tightly in the drill hole formed.Forstner drill bit with limiter


Currently Forstner drill bit for wood produced by many firms.Some focus on high-quality materials and a traditional configuration, others are trying to improve the tools for a variety of conditions.So there was a drill adapted for grinding machine.He rim behind the central incisors has a larger incision.

This drill loses some of the cutting surface of the circle, which is fraught with increase in vibration during operation and possible failures.On the other hand, this construction greatly reduces tool.

There Forstner drill with carbide plates welded on the inner cutting edges.Other designs have lateral circumferential teeth like saw.Cleanliness of the side surfaces in the treated material using a tool such lower class, but not the drill bit is overheated and thus provides a high speed drilling.Forstner drill Photo


Choosing Forstner drill bit, usually guided by the ratio quality / cost.It makes sense to define the purposes for which it is acquired: professional production and household needs.For frequent or permanent use advisable to choose high-quality drill-known and well-established firms.Their products will probably cost much more, but there is a guarantee that the instrument will last long and will meet the specs.

On the other hand, when it is necessary to use drill bits of different diameters, then their total cost will be quite high.Perhaps in this case it would be better to acquire affordable set, but includes a wide range of sizes or modifications.

should pay attention to the condition of the cutting surfaces.Sometimes opaque packaging prevents the drill control no bullies, burrs or chips on its edges.This product is better not to acquire.Manually fix serious defects without changing the profile and the geometry of the cutting edges can be very difficult.