TECHNICAL INFORMATION
418
GPI Thread Finishes
GPI THREAD FINISHES GPI refers to the “Glass Packaging Institute” which is responsible for establishing and issuing uniform standards regarding the types of finishes produced by American Glass Manufacturers. GPI replaces the former GCMI or “Glass Container Manufacturers Institute”. When a cap is designated as 15-425, it means that the diameter across the threaded area is approximately 15 millimeters. (See “T” dimension on illustration below.) The numerical 425 designates a specific style. The methods employed
in manufacturing containers and culture tubes from tubing do not include a transfer ring as commonly observed on mold blown vessels. As a result the “H” dimension may vary slightly from GPI’s published values. Since the “H” dimension is not designated in the size code, the chart below will assist in differentiating styles of finishes having similar thread diameters. The dimensions listed are averages. The finishes below appear in this catalog.
GPI Thread Finish Comparison Chart
400
415
425
430
“H” Measurements in millimeters (mm) 400 410 415 425
“T” Dimension
430
8
—
—
— 6.52
—
10
—
—
— 6.86
—
13
—
— 11.22
7.50
—
15
—
— 13.90
7.50
—
18
9.05
13.03
15.42
— 15.34
20
9.50
13.82
18.59
— 15.34
22
9.50
14.60
21.01
— 15.34
24
10.25
16.15
24.05
— 16.43
28
10.25
17.73
27.23
— 18.39
33
9.85
—
—
— 19.69
38
9.85
—
—
— 24.03
38
—
—
—
— 22.00
SUGGESTED SCREW CAP APPLICATION TORQUE
The figures at left are offered as guidelines for automatic capping machines. Obviously, variables such as cap and liner material and product characteristics play an important part in correct torque application. The recommended procedure for checking capping machine torque application is as follows: Apply caps to a representative number of product filled containers with the torque required. Then, the cap removal torque is established. Once the removal torque for a known application is established, the machine can be checked at intervals for proper application torque by measuring removal cap torque.
Cap Size
Torque
Cap Size
Torque
(Millimeters)
(Inch-Pounds)
(Millimeters)
(Inch-Pounds)
38 43 48 53 58 63 70 83 89
15-23 17-26 19-29 21-32 23-35 25-38 28-42 34-49 36-53 48-72
8
3-5 4-6 5-7 6-9
10 13 15 18 20 22 24 28 33
7-11 8-12 9-13
10-15 11-17 13-20
120
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