.

With Our Large Selection of Standardized Products, We Can Meet All Your Precision Linear Motion Requirements.

Please select the most suitable products by carefully considering the characteristics of items and contents of the product tables. It is also important to read all applicable "CAUTION" notes before the final selection. Use of catalog numbers when ordering will simplify and expedite the processing of your order.

1. Caution in Selecting the Mating Gears

(1) With the exception of helical racks, KHK stock racks can mate with any spur gears of the same module. However, the face width of a rack may not match that of the mating gear.
(2) There are limited choices of mating gears for KRHG (F) ground helical racks and SH helical racks. Make sure to take the hand of helix into account when choosing. (See table on the right.)

Selection on Mating Gear (Allowable Not allowable)
Catalog No.
 KRHG(F) SRH
RH LH RH LH
KHG LH



RH



SH LH



RH



2. Caution in Selecting Gears Based on Gear Strength

The gear strength values shown in the product pages were computed by assuming a certain application environment. Therefore, they should be used as references. We recommend that each user computes his own values by applying the actual usage conditions. The table below contains the assumptions established for these products in order to compute gear strengths.

Calculation of Bending Strength of Racks

Item Catalog No.
KRG,KRHG
KRGF,KRHGF
KRGD,KRF		 SR,SRO
SRF,SROS
SRFD,SRH		 SUR
SURF
SURO		 BSR PR
PRF		 DR
Formula Formula of spur and helical gears on bending strength(JGMA401-01) The Lewis formula
No. of teeth of mating gears 30
(30)
Rotation 100rpm
(100rpm)
Durability Over 107 cycles Allowable bending stress
Impact from motor Uniform load 1.15kgf/mm2
40 with no
lubricant
 m0.8 4.0
m1.0 3.5
m1.5 1.8
m2.0 1.2
kgf/mm2
Impact from load Uniform load
Direction of load Bidirectional
Allowable root beam stressFlim 21.33kgf/mm2 213.33kgf/mm2 27kgf/mm2 22.67kgf/mm2
Safety factor SF 1.2

Calculation of Surface Durability (Except where it is common with bending Strength)

Formula Formula of spur and helical gears on bending strength (JGMA401-01)
Kinematic viscosity of lubricant 100cSt(50)
Gear support Gears are supported on one end.
Allowable Hertz stressHlim 79kgf/mm2 52.5kgf/mm2 41.3kgf/mm2
Safety factor SH 1.15

CAUTION: Since the load is bidirectional, the allowable root bending stress Flim, calculated from JGMA 401-01, is set to 2/3 of the value. The values for DR m1.5 racks are our own estimates.

REFERENCE: JGMA (Japanese Gear Manufacturer's Association). "MC Nylon Technical Data" by Nippon Polypenco Co. and "Duracon Gear" by Polyplastic Co.


3. Selecting Racks by Precision

The precision standards of KHK stock racks are established by us. The table below indicates the tolerance ranges of our racks.

(1) Pitch Errors of Racks (KHK R 001)

The following method was used to establish our own precision grades of racks. First, the length of the rack is divided by pi () to obtain the pitch diameter of an equivalent spur gear of the same module. Then, JIS B 1702 Standards, "Precision of Spur and Helical Gears", is applied to this equivalent spur gear to obtain the error tolerances of precision grades 1 to 8.

Precision Grades of Racks (KHK R 001)

Grade Pitch error over M0.4 up to 1 over M1 up to 1.6 over M1.6 up to 2.5 over M2.5 up to 4 over M4 up to 6 over M6 up to 10
Rack length (nominal)
3
0
0		 5
0
0		 1
0
0
0		 1
5
0
0		 2
0
0
0		 3
0
0		 5
0
0		 1
0
0
0		 1
5
0
0		 2
0
0
0		 3
0
0		 5
0
0		 1
0
0
0		 1
5
0
0		 2
0
0
0		 3
0
0		 5
0
0		 1
0
0
0		 1
5
0
0		 2
0
0
0		 3
0
0		 5
0
0		 1
0
0
0		 1
5
0
0		 2
0
0
0		 3
0
0		 5
0
0		 1
0
0
0		 1
5
0
0		 2
0
0
0
1 Single pitch error 7 9 10

8 9 10 12 12 8 9 11 12 12 9 10 11 13 13 10 11 13 14 14 12 13 14 16 16
Tooth-to-tooth error 8 9 10

8 9 11 13 13 9 10 12 14 14 10 11 13 15 15 11 13 14 16 16 13 15 16 18 18
Total composite error 21 24 28

22 25 29 33 33 23 26 30 35 35 25 28 32 37 37 28 32 35 40 40 34 37 40 45 45
2 Single pitch error 10 12 14

11 12 14 17 17 12 13 15 17 17 13 14 16 18 18 14 16 18 20 20 17 18 20 23 23
Tooth-to-tooth error 12 13 16

12 14 16 19 19 13 15 17 19 19 14 15 18 21 21 16 18 20 24 24 19 21 24 27 27
Total composite error 30 34 39

31 35 41 48 48 33 37 43 49 49 36 40 46 53 53 40 45 50 57 57 48 52 58 64 64
3 Single pitch error 15 17 20

16 18 20 24 24 16 19 21 25 25 18 20 23 26 26 20 22 25 29 29 24 26 29 32 32
Tooth-to-tooth error 17 19 22

17 20 24 28 28 18 21 25 29 29 20 24 27 31 31 24 26 30 34 34 28 31 34 40 40
Total composite error 42 48 56

44 50 57 57 67 46 52 60 70 70 51 57 64 74 74 57 63 71 80 80 67 73 81 91 91
4 Single pitch error 21 24 28

22 25 29 33 33 23 26 30 35 35 25 28 32 37 37 28 32 35 40 40 34 37 40 45 45
Tooth-to-tooth error 25 28 33

26 29 34 42 42 27 31 38 43 43 30 33 40 46 46 34 39 44 50 50 42 46 51 57 57
Total composite error 60 68 79

62 71 81 95 95 66 74 85 99 99 72 81 91 105 105 81 90 100 115 115 96 105 115 130 130
5 Single pitch error 30 34 39

31 35 41 48 48 33 37 43 49 49 36 40 46 53 53 40 45 50 57 57 48 52 58 64 64
Tooth-to-tooth error 35 43 49

39 44 51 59 59 41 47 53 62 62 45 50 57 69 69 51 56 66 75 75 60 69 76 85 85
Total composite error 83 95 110

87 99 115 135 135 92 105 120 140 140 100 115 130 145 145 115 125 140 160 160 135 145 160 180 180

8 Single pitch error 160 177 206

166 184 212 232 248 173 190 219 238 254














Tooth-to-tooth error 256 283 330

266 294 339 371 397 277 304 350 381 406














Total composite error - - -

- - - - - - - - - -














Pitch inspection and a sample report using Karl Zeiss UMC-550 Coordinate Measuring Machine. (KHK R 001 Grade 1)

(2) Precision of Rack Blanks (KHK R 002)

Tolerance on Face Width and Height (unit: mm)

Face width &
height		 Precision grade
(KHK R 001)
Grade1
KRG Series		 Grade4
SR Series		 Grade5
SUR Series		 Grade8
Flexible
Racks
below 6 -
0
-0.09
-
0.25
6 up to10 0
-0.05
0
-0.09
0
-0.22
0.30
10 up to 18 0
-0.05
0
-0.11
0
-0.27
0.35
18 up to 30 0
-0.05
0
-0.13
0
-0.33
0.40
30 up to 50 0
-0.05
0
-0.16
0
-0.39
-
50 up to 90 0
-0.05
0
-0.19
0
-0.46
-

NOTE: The width and height tolerances of KHK R 001 grades 4 and 5 products are measured at 1mm inside from each corner.

Tolerance on Diameter of Round Racks

KHK stock round racks are made to h9 tolerance, except 60 (SRO 6-1000) has h10.

Tolerance on Perpendicularity, K (unit: mm)

Cross sectional dimensions
(WH) 		Precision grade
(KHK R 001)
Grade 1
KRG Series		 Grades 4 & 5
SR Series
1012 0.010 0.035
1520 0.010 0.047
2025 0.015 0.044
2530 0.015 0.052
3035 0.015 0.051
4045 - 0.065
5055 - 0.058
6060 - 0.070
7575 - 0.075
9090 - 0.080

Tolerance on Straightness, L (unit: mm)

Length (nominal) Precision grade
(KHK R 001)
Grade 1 Grades 4 & 5
500 0.05 0.2
1000 0.05 0.3
1500 - 0.3
2000 - 0.4

NOTE: The straightness tolerances of round racks are 0.15/500mm and 0.2/1000mm.
The straightness tolerances of plastic racks are 5/1000mm.

Tolerance on Overall Length (unit: mm)

Type of product Allowable error
Type F racks with machined ends O
-0.2
FRCP,DR flexible racks 10
Other racks +3
-2

4. Caution with Regard to the Special Characteristics

(1) The black oxide finish is somewhat effective in preventing rust but is not rustproof.
(2) With treatments such as solution heat treatment* :and passivation**, SUR(F) and SURO stainless steel racks can resist rusting to a great degree; yet they are not totally rustproof.
*Solution Heat Treatment
Heat treatment by which the carbon formed on the surface during the blank manufacturing is made to migrate into the material interior.
** Passivation
Immersion of the metal in nitric acid to make it more rust-resistant.
(3) Due to their material, PR (F) plastic racks may be affected by significant variations in temperature or humidity. This is especially true for the overall lengths and pitch errors.
(4) SSR, SIR corner racks are easily deformable and may develop changes in dimensions.
(5) Racks in general (but particularly long racks) have the tendency to warp with age. Caution needs to be exercised.

5. Other Points to Consider in the Selection Process

(1) KHK Co. is glad to quote items not shown in this catalog or modifications of standard products (material, module, no. of teeth, etc.).
(2) There are various footnotes to the product pages under the headings of "CAUTION" and "USEFUL HINTS". Please consider them carefully when selecting these products.
(3) There may be slight differences in color or shape of products shown in the photographs from the actual products.
(4) KHK Co. reserves the right to make changes in specifications and dimensions without notice. In the event parts you received are different from the specifications given in the table, notify us immediately.

 

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