Woodruff & Keyseat Cutters: Easy Guide to Keyway, Key, & Keyseat CNC Work

Whenever we need to affix a part to a shaft, such as a gear or pulley, keyways, keys, and keyseat work or woodruff work comes into play.  So, let's begin by getting our terminology straight.

A Keyway is a slot of some kind that is used to align the part on a shaft and prevent the part slipping as the shaft rotates.  A Key goes into the Keyway to lock things up.  Another name for a Keyway is a Keyseat, since the Key is seated in the Keyseat.  When a specialized cutter is used to cut the Keyseat, it's a Keyseat Cutter.  A Woodruff Cutter is a Keyseat Cutter.

There are several kinds of Keys in common use.

Parallel Keyways & Keys

Parallel keys are the simplest, and involve a slot that goes all the way through at least the part with the shortest axial mating length (i.e. the gear or the pulley.  Cutting a parallel key is straightforward-just use an endmill and treat it as cutting any other slot.  Alternatively, you could use a Keyseat Cutter such as a Woodruff Cutter.

Key stock is available pre-cut in standard inch and metric sizes, and the ends may either be squared or rounded.

Parallel  Inch Key Sizes

Shaft Diameter

Width

Keyway (Shaft

Keyway (Hub)

Radius r

Height

Width

Height

Width

height

Over

To/Inc

W & T

Min

Max

Max

Min

Min

Max

Min

Max

1/4

1/2

1/8

0.124

0.125

0.072

0.078

0.125

0.126

0.06

0.066

0.01

1/2

3/4

3/16

0.187

0.188

0.107

0.113

0.188

0.189

0.088

0.094

0.01

3/4

1

1/4

0.249

0.25

0.142

0.148

0.25

0.251

0.115

0.121

0.01

1

1 1/4

5/16

0.311

0.312

0.177

0.183

0.312

0.313

0.142

0.148

0.01

1 1/4

1 1/2

3/8

0.374

0.375

0.213

0.219

0.375

0.376

0.169

0.175

0.01

1 1/2

1 3/4

7/16

0.437

0.438

0.248

0.254

0.438

0.439

0.197

0.203

0.02

1 3/4

2

1/2

0.499

0.5

0.283

0.289

0.5

0.501

0.224

0.23

0.02

2

2 1/2

5/8

0.624

0.625

0.354

0.36

0.625

0.626

0.278

0.284

0.02

2 1/2

3

3/4

0.749

0.75

0.424

0.43

0.75

0.751

0.333

0.339

0.02

3

3 1/2

7/8

0.874

0.875

0.495

0.501

0.875

0.876

0.387

0.393

0.062

3 1/2

4

1

0.999

1

0.566

0.572

1

1.001

0.442

0.448

0.062

4

5

1 1/4

1.248

1.25

0.707

0.713

1.25

1.252

0.551

0.557

0.062

5

6

1 1/2

1.498

1.5

0.848

0.854

1.5

1.502

0.661

0.667

0.062

Per BS 46 Part 1 : 1958 Keys and keyways and taper pins. Specification. Keys and keyways.

Parallel Metric Key Sizes

Nominal Diameter

Key

KeyWay

d

b x h width x thck

Width b

Depth

Radius r

Nom

Tolerance Class

Shaft t1

Hub t2

Over

Incl

Free

Normal

Close/Int

Shaft

Hub

Shaft

Hub

Shaft/Hub

Nom

Tol

Nom

Tol

Max

min

H9

D10

N9

Js9

P9

6

8

2×2

2

+0,025

+0,06

• 0,004

+0,012

• 0,006

1,2

+0,1

1,0

+0,1

0,16

0,08

8

10

3×3

3

0

+0,02

• 0,029
• 0,012
• 0,031

1,8

0

1,4

0

0,16

0,08

10

12

4×4

4

+0,03

+0,078

0

+0,015

• 0,012

2,5

1,8

0,16

0,08

12

17

5×5

5

0

+0,030

• 0,030
• 0,015
• 0,042

3,0

2,3

0,25

0,16

17

22

6×6

6

3,5

2,8

0,25

0,16

22

30

8×7

8

+0,036

+0,098

0

+0,018

• 0,015

4,0

+0,2

3,3

+0,2

0,25

0,16

30

38

10×8

10

0

+0,040

• 0,036
• 0,018
• 0,051

5,0

0

3,3

0

0,40

0,25

38

44

12×8

12

+0,043

+0,12

0

+0,021

• 0,018

5,0

+0,2

3,3

+0,2

0,40

0,25

44

50

14×9

14

0

+0,050

• 0,043
• 0,021
• 0,061

5,5

0

3,8

0

0,40

0,25

50

58

16×10

16

6,0

4,3

0,40

0,25

58

65

18×11

18

7,0

4,4

0,40

0,25

65

75

20×12

20

+0,052

+0,149

0

+0,026

• 0,022

7,5

4,9

0,60

0,40

75

85

22×14

22

0

+0,065

• 0,052
• 0,026
• 0,074

9,0

5,4

0,60

0,40

85

95

25×14

25

9,0

5,4

0,60

0,40

95

110

28×16

28

10,0

6,4

0,60

0,40

110

130

32×18

32

+0,062

+0,18

0

+0,031

• 0,026

11,0

7,4

0,6

0,4

130

150

36×20

36

0

+0,080

• 0,062
• 0,031
• 0,088

12,0

+0,3

8,4

+0,3

1,0

0,7

150

170

40×22

40

13,0

0

9,4

0

1,0

0,7

170

200

45×25

45

15,0

10,4

1,0

0,7

200

230

50×28

50

17,0

11,4

1,0

0,7

230

260

56×32

56

+0,074

+0,220

0

+0,037

• 0,032

20,0

12,4

1,6

1,2

260

290

63×32

63

0

0,100

• 0,074
• 0,037
• 0,106

20,0

12,4

1,6

1,2

290

330

70×36

70

22,0

14,4

1,6

1,2

330

380

80×40

80

25,0

15,4

2,5

2,0

380

440

90×45

90

+0,087

+0,260

0

+0,043

• 0,037

28,0

17,4

2,5

2,0

440

500

100×50

100

0

0,120

• 0,087
• 0,043
• 0,124

31,0

20

2,5

2,0

Per BS 4235-1:1972: Specification for metric keys and keyways - Parallel and taper keys.

Woodruff Keyways & Keys

Woodruff Keys are an alternative to Parallel Keys.  They are semi-circular, and fit into a Keyway shaped as a circular-segment in the shaft and a rectangular slot in the mating part.  The semi-circular slot is cut by plunging a Woodruff Cutter (the correct Keyseat Cutter  for this style Keyway) into the workpiece.

The advantages of Woodruff Keys over Parallel Keys are:

• They eliminate the milling near shaft shoulders which reduces stress concentrations and makes it easier to maintain circularity constraints.
• They are therefore better suited to higher speed operation of the rotating shaft.
• The key typically has a more exact fit which reduces play and improves the reliability of the key.
• A Woodruff key may be easier to remove with a hammer blow since the circular profile will push the key out of the slot.  A Parallel key requires the key to be pushed axially a longer distance.

Woodruff Keys were developed in 1888 by W.N. Woodruff of Connecticut, USA.

Woodruff keys may be full radius or flat bottom, but the keyseat will always be radiused by the Keyseat Cutter / Woodruff Cutter.  A flat bottom Woodruff Key has part of the radius shaved right at the bottom:

Woodruff Key Dimensions (Inch)

Like Parallel Keys, Woodruff Keys come in standard sizes:

KEY NUMBER

KEY DIMENSIONS

SHAFT DIAMETER

HEIGHT OF KEY ABOVE SHAFT

DEPTH OF KEYWAY

DIAMETER

WIDTH

MINIMUM

MAXIMUM

204

1/2

1/16

5/16

3/8

0.0312

0.1718

304

1/2

3/32

5/16

1/2

0.0469

0.1 561

404

1/2

1/8

9/16

3/4

0.0625

0.1405

405

5/8

1/8

9/16

3/4

0.0625

0.1875

505

5/8

5/32

13/16

15/16

0.0781

0.1719

406

3/4

1/8

11/16

3/4

0.0625

0.2505

606

3/4

3/16

1

1 1/8

0.0937

0.2193

507

7/8

5/32

1 1/8

15/16

0.0781

0.2969

807

7/8

1/4

1  5/16

1 1/8

0.125

0.25

608

1

5/16

1

1  7/16

0.0937

0.3443

1008

1

5/16

1  1/16

1 5/8

0.1562

0.2818

609

1 1/8

5/16

1  1/16

1  7/16

0.0937

0.3903

810

1 1/4

1/4

1 1/4

1 3/4

0.125

0.422

1210

1 1/4

3/8

1 1/2

1 7/8

0.1875

0.3595

1011

1 3/8

1/2

1 13/16

2

0.1562

0.4378

Woodruff Key Dimensions (Metric)

w x  h1  x  D......

Width b

Depth

Radius R

Nom

Tolerance Class

Shaft t1

Hub t2

Normal

Close

Shaft

Hub

Shaft & Hub P6

Nom

Tol

Nom

Tol

Max

min

N9

Js9

1,0 x 1,4 x 4

1

• 0,004

+0,012

• 0,006

1,0

+0,1

0,6

+0,1

0,16

0,08

1,5 x 2,6 x 7

1,5

• 0,029
• 0,012
• 0,0031

2,0

0

0,8

0

0,16

0,08

2,0 x 2,6 x 7

2,0

1,8

1,0

0,16

0,08

2,0 x 3,7 x 10

2,0

2,9

1,0

0,16

0,08

2,5 x 3,7 x 10

2,5

2,7

1,2

0,16

0,08

3,0 x 5,0 x 13

3,0

3,8

+0,2

1,4

0,16

0,08

3,0 x 6,5 x 16

3,0

5,3

0

1,4

0,16

0,08

4,0 x 6,5 x 16

4,0

0

+0,015

• 0,012

5,0

1,8

0,25

0,16

4,0 x 7,5 x 19

4,0

• 0,030
• 0,015
• 0,042

6,0

1,8

0,25

0,16

5,0 x 6,5 x 16

5,0

4,5

2,3

0,25

0,16

5,0 x 7,5 x 19

5,0

5,5

2,3

0,25

0,16

5,0 x 9.0 x 22

5,0

7,0

+0,3

2,3

0,25

0,16

6,0 x 9,0 x 22

6,0

6,5

0

2,8

0,25

0,16

6,0 x 11,0 x 28

6,0

7,5

2,8

+0,2

0,25

0,16

8,0 x 11,0 x 28

8,0

0

+0,018

+0,015

8,0

3,3

0

0,40

0,25

10,0 x 13,0 x 32

10,0

• 0.036
• 0.018
• 0.051

10,0

3,3

0,4

0,25

Keyseat Cutters (aka Woodruff Cutters or Woodruff Key Cutters)

Woodruff Keys take a special Keyseat Cutter called a Woodruff Cutter.  It's basically a small saw.  They look like this:

Woodruff Cutters are a subset of the broader category of Slotting Cutters.

A Woodruff Cutter may be constructed from HSS or Solid Carbide.  The solid carbide versions are capable of both higher material removal rates (e.g. shorter cycle times) and longer tool life, so they are often preferred for production work.

Woodruff Cutter & Keyseat Cutter Feeds and Speeds Calculator

Woodruff and Keyseat Cutters behave like Saws.  Learn a lot more tips and deeper feeds and speeds info from our article on Slitting Saw Feeds and Speeds, Tips, and Techniques.

Our G-Wizard Feeds and Speeds Calculator has special support for Woodruff Cutters & Keyseat Cutters. To set up the Woodruff Cutter cut in the Calculator, we go left to right, top to bottom:

1. Select the Machine

2. Select the Material

3. Select the Woodruff Cutter from the tool menu (Note:  Keyseat cutters are referred to as Woodruff cutters for feeds and speeds):

4. Select what material the tool is made from, either HSS or Solid Carbide, and what coating it has (if any).  A good coating can provide some added lubricity to make the material cut more easily.

5. Enter your cutter’s diameter and number of teeth.

6. Enter your cutter’s thickness

7. You can optionally add information such as shank length, neck diameter, and overall length.  This information won't affect feeds and speeds but will make your tool tables more complete.

8. Enter the Depth of Cut. This is the total depth of the keyseat.  G-Wizard should remind you to keep cut depth less than 4x saw thickness:

Note that in the case of a Woodruff key, you want to choose a saw diameter (cut diameter) that is equal to your woodruff key's diameter.

Here is the finished result:

Typical setup to find Feeds and Speeds for a Slitting Saw…

If you’re not a registered G-Wizard user and you’d like to try our free 30-day trial, check it out on this page.

Sneaky Stuff:  What Else Can a Woodruff Cutter Do?

They can be quit useful for making undercuts in a workpiece.