Gear ratios – Smithy Midas 1220 XL User Manual
Page 37
Gear Ratios
The lathe lets you use various indicated gear combinations to cut the desired number of
threads per inch (tpi), or the metric equivalent, or to advance the tool at a specified
amount each revolution (feed rate expressed as inches per revolution (ipr))
The Midas 1220 XL has a pick-gear gearbox (Figure 5.2); gears are picked and placed to
change the gear ratios. The gearbox mechanism determines the leadscrew's rotation rate
in relation to the spindle's for threading, turning and facing. To change the thread pitch
(tpi), replace the gears per Table 7.2.
Table 7.2 Gear Ratios
Threads Per Inch
Metric Pitches
1
2
A
B
C
D
.003
.006
30
60
27
63
30
15
70
32
40
45
28
14
70
32
40
42
26
13
70
32
40
39
24
12
70
32
40
36
22
11
70
32
40
33
20
10
70
32
40
30
18
9
70
27
45
36
16
8
70
27
45
32
14
7
60
27
60
32
12
6
70
27
60
32
A
B
C
D
E
MM
Speeds Gear Position
Speeds Gear Position
1
2
A
B
C
D
0.50
1.00
49
32
42
56
0.60
49
32
45
50
0.70
49
32
42
40
0.75
1.50
63
32
42
48
0.80
49
50
60
32
1.75
49
48
63
32
1.00
2.00
63
32
49
42
1.25
2.50
60
32
49
32
1.50
3.00
63
32
56
32
7-3
Or Visit www.smithy.com
Turning