Keyway, Key, & Keyseat Work with Keyseat Cutters

Whenever we need to affix a part to a shaft, such as a gear or pulley, keyways, keys, and keyseat 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 keyways and 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 +0,021 -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 +0,031 -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 key woodruff key cutter

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:

flat bottom woodruff key

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 +0,015 -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 +0,018  +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 cutter woodruff key cutter keyseat cutter

Woodruff Cutter & Keyseat Cutter Feeds and Speeds Calculator

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, either HSS or Carbide:

slitting saw speeds and feeds calculator

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

5. Enter your cutter’s thickness

6. Enter the Depth of Cut. This is the total depth of the keyseat.

Here is the finished result:

slitting saw feeds and speeds calculator carbide hss

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.

 

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