Metric threading, “b” gear engages the 120 tooth idler gear
Carriage travel in mm per spindle revolution
Top row is the “a” gear, left column is the “b” gear.
Gear box in position IA
27
36
40
44
45
46
48
52
56
60
27
na
na
na
na
na
na
na
na
na
na
36
1.0000
1.4815
1.6296
1.6667
1.7037
1.7778
1.9259
2.0741
2.2222
40
0.9000
1.2000
1.4667
1.5000
1.5333
1.6000
1.7333
1.8667
2.0000
44
0.8182
1.0909
1.2121
1.3636
1.3939
1.4545
1.5758
1.6970
1.8182
45
0.8000
1.0667
1.1852
1.3037
1.3630
1.4222
1.5407
1.6593
1.7778
46
0.7826
1.0435
1.1594
1.2754
1.3043
1.3913
1.5072
1.6232
1.7391
48
0.7500
1.0000
1.1111
1.2222
1.2500
1.2778
1.4444
1.5556
1.6667
52
0.6923
0.9231
1.0256
1.1282
1.1538
1.1795
1.2308
1.4359
1.5385
56
0.6429
0.8571
0.9524
1.0476
1.0714
1.0952
1.1429
1.2381
1.4286
60
0.6000
0.8000
0.8889
0.9778
1.0000
1.0222
1.0667
1.1556
1.2444
Gear box in position IIA
27
36
40
44
45
46
48
52
56
60
27
na
na
na
na
na
na
na
na
na
na
36
0.8330
1.2341
1.3575
1.3883
1.4192
1.4809
1.6043
1.7277
1.8511
40
0.7497
0.9996
1.2217
1.2495
1.2773
1.3328
1.4439
1.5549
1.6660
44
0.6815
0.9087
1.0097
1.1359
1.1612
1.2116
1.3126
1.4136
1.5145
45
0.6664
0.8885
0.9873
1.0860
1.1353
1.1847
1.2834
1.3822
1.4809
46
0.6519
0.8692
0.9658
1.0624
1.0865
1.1590
1.2555
1.3521
1.4487
48
0.6248
0.8330
0.9256
1.0181
1.0413
1.0644
1.2032
1.2958
1.3883
52
0.5767
0.7689
0.8544
0.9398
0.9612
0.9825
1.0252
1.1961
1.2815
56
0.5355
0.7140
0.7933
0.8727
0.8925
0.9123
0.9520
1.0313
1.1900
60
0.4998
0.6664
0.7404
0.8145
0.8330
0.8515
0.8885
0.9626
1.0366
Gear box in position IIIA
27
36
40
44
45
46
48
52
56
60
27
na
na
na
na
na
na
na
na
na
na
36
1.1667
1.7280
1.9008
1.9445
1.9877
2.0741
2.2470
2.4198
2.5927
40
1.0500
1.4000
1.7107
1.7501
1.7889
1.8667
2.0223
2.1778
2.3334
44
0.9546
1.2728
1.4142
1.5910
1.6263
1.6970
1.8384
1.9799
2.1213
45
0.9334
1.2445
1.3828
1.5210
1.5902
1.6593
1.7976
1.9359
2.0741
46
0.9131
1.2174
1.3527
1.4880
1.5218
1.6232
1.7585
1.8938
2.0290
48
0.8750
1.1667
1.2963
1.4260
1.4584
1.4908
1.6852
1.8149
1.9445
52
0.8077
1.0770
1.1966
1.3163
1.3462
1.3761
1.4359
1.6753
1.7949
56
0.7500
1.0000
1.1111
1.2223
1.2500
1.2778
1.3334
1.4445
1.6667
60
0.7000
0.9334
1.0371
1.1408
1.1667
1.1926
1.2445
1.3482
1.4519
Metric – data in mm
Metric threading, “b” gear engages the 120 tooth idler gear
Carriage travel in mm per spindle revolution
Top row is the “a” gear, left column is the “b” gear.
Gear box in position IB
27
36
40
44
45
46
48
52
56
60
27
na
na
na
na
na
na
na
na
na
36
2.0000
2.9630
3.2593
3.3333
3.4074
3.5556
3.8519
4.1481
4.4444
40
1.8000
2.4000
2.9333
3.0000
3.0667
3.2000
3.4667
3.7333
4.0000
44
1.6364
2.1818
2.4242
2.7273
2.7879
2.9091
3.1515
3.3939
3.6364
45
1.6000
2.1333
2.3704
2.6074
2.7259
2.8444
3.0815
3.3185
3.5556
46
1.5652
2.0870
2.3188
2.5507
2.6087
2.7826
3.0145
3.2464
3.4783
48
1.5000
2.0000
2.2222
2.4444
2.5000
2.5556
2.8889
3.1111
3.3333
52
1.3846
1.8462
2.0513
2.2564
2.3077
2.3590
2.4615
2.8718
3.0769
56
1.2857
1.7143
1.9048
2.0952
2.1429
2.1905
2.2857
2.4762
2.8571
60
1.2000
1.6000
1.7778
1.9556
2.0000
2.0444
2.1333
2.3111
2.4889
Gear box in position IIB
27
36
40
44
45
46
48
52
56
60
27
na
na
na
na
na
na
na
na
na
na
36
1.6660
2.4681
2.7150
2.7767
2.8384
2.9618
3.2086
3.4554
3.7022
40
1.4994
1.9992
2.4435
2.4990
2.5545
2.6656
2.8877
3.1099
3.3320
44
1.3631
1.8175
2.0194
2.2718
2.3223
2.4233
2.6252
2.8272
3.0291
45
1.3328
1.7771
1.9745
2.1720
2.2707
2.3694
2.5669
2.7643
2.9618
46
1.3038
1.7384
1.9316
2.1248
2.1730
2.3179
2.5111
2.7042
2.8974
48
1.2495
1.6660
1.8511
2.0362
2.0825
2.1288
2.4064
2.5916
2.7767
52
1.1534
1.5378
1.7087
1.8796
1.9223
1.9650
2.0505
2.3922
2.5631
56
1.0710
1.4280
1.5867
1.7453
1.7850
1.8247
1.9040
2.0627
2.3800
60
0.9996
1.3328
1.4809
1.6290
1.6660
1.7030
1.7771
1.9252
2.0732
Gear box in position IIIB
27
36
40
44
45
46
48
52
56
60
27
na
na
na
na
na
na
na
na
na
36
2.3340
3.4578
3.8036
3.8900
3.9764
4.1493
4.4951
4.8409
5.1867
40
2.1006
2.8008
3.4232
3.5010
3.5788
3.7344
4.0456
4.3568
4.6680
44
1.9096
2.5462
2.8291
3.1827
3.2535
3.3949
3.6778
3.9607
4.2436
45
1.8672
2.4896
2.7662
3.0428
3.1812
3.3195
3.5961
3.8727
4.1493
46
1.8266
2.4355
2.7061
2.9767
3.0443
3.2473
3.5179
3.7885
4.0591
48
1.7505
2.3340
2.5933
2.8527
2.9175
2.9823
3.3713
3.6307
3.8900
52
1.6158
2.1545
2.3938
2.6332
2.6931
2.7529
2.8726
3.3514
3.5908
56
1.5004
2.0006
2.2229
2.4451
2.5007
2.5563
2.6674
2.8897
3.3343
60
1.4004
1.8672
2.0747
2.2821
2.3340
2.3859
2.4896
2.6971
2.9045
Metric – data in mm
Metric threading, “b” gear engages the 120 tooth idler gear
Carriage travel in mm per spindle revolution
Top row is the “a” gear, left column is the “b” gear.
Gear box in position IC
27
36
40
44
45
46
48
52
56
60
27
na
na
na
na
na
na
na
na
na
na
36
0.5000
0.7407
0.8148
0.8333
0.8519
0.8889
0.9630
1.0370
1.1111
40
0.4500
0.6000
0.7333
0.7500
0.7667
0.8000
0.8667
0.9333
1.0000
44
0.4091
0.5455
0.6061
0.6818
0.6970
0.7273
0.7879
0.8485
0.9091
45
0.4000
0.5333
0.5926
0.6519
0.6815
0.7111
0.7704
0.8296
0.8889
46
0.3913
0.5217
0.5797
0.6377
0.6522
0.6957
0.7536
0.8116
0.8696
48
0.3750
0.5000
0.5556
0.6111
0.6250
0.6389
0.7222
0.7778
0.8333
52
0.3462
0.4615
0.5128
0.5641
0.5769
0.5897
0.6154
0.7179
0.7692
56
0.3214
0.4286
0.4762
0.5238
0.5357
0.5476
0.5714
0.6190
0.7143
60
0.3000
0.4000
0.4444
0.4889
0.5000
0.5111
0.5333
0.5778
0.6222
Gear Box in position IIC
27
36
40
44
45
46
48
52
56
60
27
na
na
na
na
na
na
na
na
na
na
36
0.4165
0.6170
0.6787
0.6942
0.7096
0.7404
0.8021
0.8639
0.9256
40
0.3749
0.4998
0.6109
0.6248
0.6386
0.6664
0.7219
0.7775
0.8330
44
0.3408
0.4544
0.5048
0.5680
0.5806
0.6058
0.6563
0.7068
0.7573
45
0.3332
0.4443
0.4936
0.5430
0.5677
0.5924
0.6417
0.6911
0.7404
46
0.3260
0.4346
0.4829
0.5312
0.5433
0.5795
0.6278
0.6761
0.7243
48
0.3124
0.4165
0.4628
0.5091
0.5206
0.5322
0.6016
0.6479
0.6942
52
0.2883
0.3845
0.4272
0.4699
0.4806
0.4913
0.5126
0.5981
0.6408
56
0.2678
0.3570
0.3967
0.4363
0.4463
0.4562
0.4760
0.5157
0.5950
60
0.2499
0.3332
0.3702
0.4072
0.4165
0.4258
0.4443
0.4813
0.5183
Gear box in position IIIC
27
36
40
44
45
46
48
52
56
60
27
na
na
na
na
na
na
na
na
na
na
36
0.5834
0.8642
0.9506
0.9723
0.9939
1.0371
1.1235
1.2099
1.2963
40
0.5250
0.7000
0.8556
0.8750
0.8945
0.9334
1.0111
1.0889
1.1667
44
0.4773
0.6364
0.7071
0.7955
0.8132
0.8485
0.9192
0.9899
1.0606
45
0.4667
0.6222
0.6914
0.7605
0.7951
0.8297
0.8988
0.9679
1.0371
46
0.4565
0.6087
0.6763
0.7440
0.7609
0.8116
0.8793
0.9469
1.0145
48
0.4375
0.5834
0.6482
0.7130
0.7292
0.7454
0.8426
0.9074
0.9723
52
0.4039
0.5385
0.5983
0.6581
0.6731
0.6881
0.7180
0.8376
0.8975
56
0.3750
0.5000
0.5556
0.6111
0.6250
0.6389
0.6667
0.7222
0.8334
60
0.3500
0.4667
0.5185
0.5704
0.5834
0.5963
0.6222
0.6741
0.7259
Metric – data in mm
Gear ratios and formulas.
Ratio of gear train output (input to gear box) = Z
Z = 40/60 x “a”/127 x 120/”b”
Example: “a” = 44, “b” = 46
One turn of the spindle will result in 0.6025 turns of the gearbox input shaft.
The lead screw is 12 TPI or 0.0833” or 2.1167mm.
Gear box ratios:
Position “A” = 1:1
Position “B” = 1:2
Position “C” = 2:1
Position I = 1:1
Position II = 1:0.833
Position III = 1:1.1667
Overall gearbox ratios:
C
A
B
II
0.4165
0.8330
1.6660
I
0.5000
1.0000
2.0000
III
0.5834
1.1667
2.3340
One turn on the input shaft will result in the lead screw turning at the rate shown in the above table.