Router

How it works

The bit is held in a collet on the motor shaft, and the motor turns it at many thousands of revolutions per minute. The router rests on a flat base, and the depth of the cut is set by how far the bit projects below the base. The cutting edges of the bit remove wood as the router is moved along the work, which must be clamped to a stable support.

The bit rotates clockwise as seen from the top of the tool. Bosch’s manual explains that the direction of feed relates to the direction of bit rotation and that the most efficient cut is made by feeding the router so that the bit turns into the work, not away from it. Feeding in the wrong direction causes the cutting edge to climb out of the work and pull the tool in the direction of feed.

Anatomy

Motor housing: Contains the motor whose armature shaft carries the collet; in George Kelley’s 1908 patent the cutters are driven from the armature shaft of an electric motor enclosed in the frame.
Collet and collet nut: Grip the shank of the bit. Bosch’s routers list collet capacities of 1/4, 3/8 and 1/2 inch and 8 mm.
Base (sub-base): The flat plate on which the router rides; its opening limits the cutting diameter of the bit that can be used.
Depth adjustment: On Bosch’s plunge base a depth rod and a stepped depth stop turret set plunging depth in 1/8-inch steps, with a fine adjustment of 1/32 inch per turn.
Speed control: An electronic speed dial matches motor speed to cutter size and material hardness on the models Bosch describes.
Handles and switch: The router is held with two hands; Bosch’s 1617 model has a rocker switch on the motor housing.

Variants

Fixed-base router: The motor is locked at a set depth in a base; the Bosch RA1161 is a fixed-base shop router base.
Plunge router: The bit is plunged into the work to a depth set by a depth rod and stepped turret; the Bosch RA1166 is a plunge base of this kind.
Router table: The router is mounted in a table, and the work is fed against a fence or against a piloted bit. Bosch publishes separate safety rules for this use.
Early shaper and router (Carter): Ray Carter’s 1922 patent describes a small, light shaper, held by one hand, consisting of a casing that encloses a high-speed motor with rotary cutters on the armature shaft; his 1924 patent describes a portable routing and profiling machine with a fan on the shaft.
Overarm router and pedestal shaper: VintageMachinery.org lists overarm routers and pedestal shapers among stationary woodworking machines made by Stanley Electric Tools.

Specifications

Collet capacities · in / mm: 1/4, 3/8, 1/2 in and 8 mm (on the Bosch 1617 series)Manufacturer figure for the Bosch 1617 series; other models differ.
Speed range · rpm: 8,000–25,000 rpm (Bosch 1617EVS dial settings)Bosch’s dial recommends the lowest settings for nonferrous metals and larger bits and the highest for softwoods, plastics and smaller bits. In 1928 a Carter router was advertised at 18,000 rpm.
Plunge depth step · in: 1/8 in per step on the turretBosch RA1166 plunge base.

Made to

EN 62841-2-17
UL 62841-2-17
IEC 62841-1

Safety and care

Safety

Bosch’s manual advises holding the tool by its insulated gripping surfaces, because the cutter may contact hidden wiring or its own cord.
Bosch advises securing the workpiece with clamps or another practical way to a stable platform, and never holding the workpiece in one hand and the tool in the other.
Bosch advises making sure the work surface is free from nails and other foreign objects, since cutting into a nail can make the bit and tool jump.
Bosch advises holding the tool with two hands during start-up because the reaction torque of the motor can twist the tool, and never starting the tool when the bit is engaged in the material.
Bosch advises never using dull or damaged bits, never using a bit whose cutting diameter exceeds the opening in the base, and using accessories whose rated speed is at least the maximum speed marked on the tool.
Bosch advises never touching the bit during or immediately after use, because it is too hot to touch, and not laying the tool down until the motor has come to a complete standstill.
Bosch advises wearing safety goggles and a dust mask, and working in a well ventilated area.

Care

Bosch advises that the collet chuck be cleaned occasionally with compressed air, that the taper in the armature shaft be cleaned with a tissue or fine brush, and that worn or damaged collet chucks be replaced immediately.
Bosch advises that the bit shank and chuck be clean and free of dust, wood residue and grease before assembling.

Tips

Feed against the rotation of the bit
Bosch gives the rule for a fixed-base router viewed from above: the bit rotates clockwise, so the feed direction of the cut must be counter-clockwise, with different directions for inside and outside cuts as the manual’s figure shows. A wrong direction of feed makes the tool hard to control.1
Seat the shank, then back it out
Bosch instructs inserting the shank of the bit as far as it will go into the collet, then backing it out until the cutters are about 1/8 to 1/4 inch from the face of the collet nut. For proper grip and minimum run-out the shank must be inserted at least 5/8 inch, and the collet must never be tightened without a bit.1
Match speed to bit diameter
The speed chart in Bosch’s manual puts larger diameter bits and nonferrous metals at the low settings (8,000 to 16,500 rpm) and softwoods, plastics, counter tops and smaller bits at the high settings (20,000 to 25,000 rpm). The manual adds that the bit manufacturer may also give a speed recommendation.1
Take a deep cut in progressive passes with the depth turret
For deeper cuts Bosch says to start with the highest step on the depth turret and rotate it to progressively lower steps after each cut until the final depth is reached. Steps progress by 1/8 inch, and the manual suggests test cuts in scrap before beginning work.1
Use the shortest bit that makes the cut
Bosch advises always using router bits with the shortest cutting length necessary, which minimizes run-out and chatter. The manual lists the wrong direction of feed, feeding too fast, a dull bit, a cut too large for one pass and feeding too slowly, which leaves friction burns, as causes when a router is hard to control, heats up, runs very slowly or leaves an imperfect cut.1
Use a piloted bit on a router table without a fence
Bosch’s table instructions state that when the table is used without the fence, piloted (bearing) bits must be used for internal and external contours, because the bearing helps maintain control of the workpiece; the starter pin should also be used when possible.1

History

Earliest documented

filed 23 July 1906; patented 28 January 1908

Buffalo, New York

George L. Kelley of Buffalo filed the application for a Routing Machine on 23 July 1906, and US Patent 877,894 was issued on 28 January 1908, assigned by mesne assignments to the Stevenson Machine Company of Buffalo. The specification describes a portable routing machine for working wood, particularly for cutting the grooves in stairs that receive the risers and treads, in which two cutters are driven from the armature shaft of an electric motor enclosed in the frame, and which is clamped to the board and guided by a pattern plate. VintageMachinery.org describes Kelley as the man generally recognized as inventing the handheld router.1 2

The router in its present form combines three older ideas: a rotary cutter, a small electric motor, and a base that guides the cutter against the work. Kelley’s patent shows all three. His routing machine carries its cutters on vertical shafts geared to an extension of an electric motor’s armature shaft, in a casing that, the specification says, encloses the cutters and the motor to guard the operator, and it is clamped to the board and guided by a pattern plate. It was built with a specific job in mind, the grooves in stairs, though the patent says the machine is capable of a great variety of uses.

Ray Carter made the tool portable by hand. His 1922 patent describes a light, easily portable shaper consisting of a hollow casing enclosing a high-speed electric motor, with cutters of various types on the armature shaft, to be held and operated by one hand for patternmakers, cabinetmakers and carpenters. His 1924 patent describes the same idea as a router for routing, shaping and profiling wood or metal, with an insulated casing, a fan on the shaft for cooling, a flexible cord connecting to an ordinary lamp socket and interchangeable tool holders. VintageMachinery.org counts 22 patents issued to Carter in the decade, mostly related to routers, covering bits, collets, tool grinders, dovetail jigs and butt mortising gauges.

Distribution followed corporate consolidation. According to VintageMachinery.org, Stanley formed its electric tool subsidiary in November 1929 and announced the purchase of Carter’s company the next month, then moved the business to New Britain, Connecticut, where it operated as the R. L. Carter Division; Stanley also made overarm routers and pedestal shapers. The same source records that Stanley appears to have left electric tools when its New Bern plant was sold to Bosch in 1980. The Bosch manual cited here, issued in 2018, describes the present form: interchangeable fixed and plunge bases, collets from 1/4 to 1/2 inch, and electronic variable speed with a range of 8,000 to 25,000 rpm.

The sources read do not establish when the plunge base appeared or who introduced it, and they do not show what the router displaced. The Bosch manual and Carter’s patents agree on the principal use: cutting an edge profile or groove in a single pass or in progressively deeper passes, guided by hand against an edge, a fence, a template or a bearing.

Timeline

1906
George L. Kelley applies for a patent on a portable electric routing machine (filed 23 July).1
1908
Kelley’s US Patent 877,894 is issued on 28 January.1
1922
Ray L. Carter of Syracuse, New York, files on 17 April for a light shaper with a high-speed motor and cutters on the armature shaft; US Patent 1,433,497 is issued 24 October. VintageMachinery.org says R. L. Carter Co. was formed at about the same time to make these routers.1 2
1923
R. L. Carter Co., Inc. is incorporated in Syracuse with $25,000 capital to make electric hand shapers and routers, according to a 1923 Iron Age item quoted by VintageMachinery.org; Carter files for the portable routing and profiling machine patent on 29 September.1 2
1924
US Patent 1,514,894, Portable Routing and Profiling Machine, is issued on 11 November. A July 1924 Merchandising Week item announces a new electric router from the company.1 2
1928
A Power Engineering item quoted by VintageMachinery.org describes Carter shapers and routers of light weight, operated from any lamp socket at 18,000 rpm.1
1929
The Stanley Works incorporates Stanley Electric Tool Co. on 7 November and announces the purchase of R. L. Carter Co., Inc. the following month.1 2
1936
Stanley Works (R. L. Carter Division) publishes catalog no. 55, Carter equipment for the woodworking industry.1
1980
The power tool division of The Stanley Works, with its New Bern, North Carolina plant, is acquired by Robert Bosch, which establishes the Robert Bosch Power Tool Corporation there, according to the Bosch U.S. history quoted by VintageMachinery.org.1

Where the sources disagree

Who invented the hand-held electric router?

George L. Kelley, whose 1908 patent covers a portable routing machine with an electric motor; VintageMachinery.org says he is generally recognized as the inventor of the handheld router.1 2
Patent 877,894; VintageMachinery.org
Ray L. Carter developed the first successful general-purpose router, according to a VintageMachinery.org note on Carter’s patent 1,433,497; the same site says his first attempt was a modified electric tool for barbers.1 2
VintageMachinery.org

When did Stanley acquire R. L. Carter Co.?

Late 1929: Stanley announced the purchase of R. L. Carter Co., Inc. in the month after its Electric Tool subsidiary was incorporated on 7 November 1929.1 2
VintageMachinery.org (Carter and Stanley histories, citing the Hartford Courant, 8 November 1929, and the Akron Beacon Journal, 18 December 1929)
The early 1930s: a note on Carter’s patents says the business was acquired by Stanley in the early 1930s.1
VintageMachinery.org (patent annotations)

Gaps in the record (6)

Wikipedia gives 1906 as the patent date of Kelley’s router and credits ELU of Germany with inventing the plunge router around 1949; the patent record shows filing in 1906 and issue in 1908, and no usable primary or published source for the ELU date was located, so the plunge router’s origin is left open.
Onsrud’s 1915 air-powered Jet Motor Hand Router, mentioned in lead material, was not verified from a company source.
The connection of Carter’s designs to the later Stanley and Bosch routers is documented only through VintageMachinery.org, a hobbyist reference compiled from trade journals and patents; the Bosch 1980 acquisition is quoted from the Bosch U.S. website via that site and the website itself was not reached.
Stanley and Carter catalogs on the Internet Archive were found but had no extracted text.
The history of router bit design (carbide tipping, bearing-guided bits) is not covered.
Standard slugs are guesses and have not been checked against the standards themselves.

Oscillating multi-tool