〔 PRODUCT DATA 〕 CALCULATING HEATER CAPACITY/TAPERED SCREWS FOR JIS TUBES
〔 PRODUCT DATA 〕 COOLING–USE PLUG ATTACHMENT FEMALE THREADS
■ Calculating Heater Capacity ■ Formula
■ Explanation of Cooling–use Plug Attachment Female Threads
• Please process using a tap meant for JIS tube tapered thread (PT). • Please note that tapping the female thread with a straight thread tap (PS, PF) for tubes will result in only some threads being seated, as shown in the illustration, which could lead to leakage of water. • Please note that the tapered thread for American tubing (NPT) has a different number of threads than the tapered thread for JIS tubing (PT), making them completely incompatible.
○ When used with a JIS tube tapered thread (PT) tap
× When used with a JIS tube straight thread (PS, PF) tap
W 1 (kg) × C (kcal/m∙h∙°C) × (T1–T2) 860 × h (Hour) × η (efficiency)
Cooling-use Plug
Cooling-use Plug
Heater capacity {kW} =
R (PT)
R (PT)
JIS tapered external thread
JIS tapered external thread
Rc (PT)
(PS,PF)
JIS tapered internal thread
Straight internal thread
W 1 (kg): total weight of the heated section
C (kcal/m∙h∙°C): specific heat
T1 (°C): risen temperature
T2 (°C): ambient temperature
860: 1kWh = 860kcal η (efficiency): an effective percentage contributing to heating (Example) S uppose that an entire mold is controlled by the heater, and that the weight of the mold is 130 kg, the ambient temperature is 21°C, the setting temperature of the mold is 110°C, and heating time is 30 minutes. The heater capacity that is required for the mold in this case using the above formula is calculated as follows. h (Hour): heating time
Threads are seated.
Only a few threads are seated.
■ Dimensions of the Prepared Hole for Tapered Internal Threads for JIS Tubing (reference values)
W 1 = 130 (kg) C = 0.11 (kcal/h∙m∙°C) T1 = 110 (°C) T2 = 20 (°C) h = 0.5 (30 minutes) η (efficiency) = 0.5
Prepared hole depth (f)
Prepared hole diameter recommended value (d 2 )
130 × 0.11 × (110–21) 860 × 0.5 (h) × ※ 0.5 ≒
Drill
Nominal size (No.)
Tapered thread (PT)
④ Dangerous
① Unsuitable
② Dangerous
③ Optimum
⑤ or greater
6 {kW}
( ※ Efficiency is assumed as 0.5.)
Recommended value
17 or greater
d 2
1 PT 1/8
8.5
■ Heater Selection Suppose a mold size of (230 × 270) and the outside diameter of the heater to be used as φ 12.6 and it's length as 250mm. The wattage of the MCH12.6–250 is 950W. Therefore the required number of heaters would be 6000W ÷ 950W ≒ 6 (heaters) This was a rather simple example. Actually, it is difficult to compute η (efficiency) and it is necessary to raise η (efficiency) by insulating the heated area and through uniform positioning of the heaters. Generally, a value between 0.2–0.5 is appropriate for η (efficiency). In addition, please be aware of the fact that temperature and heat are entirely different things.
■ Terminology Specific heat: With a unit of (kcal/h∙m∙°C), it is the amount of heat required to raise the temperature of mass m by 1(°C) within the unit time. If the temperature of an object of mass m and specific heat C(kcal/h∙m∙°C) rises by t°C, with absorbed heat of Q (kcal), the relationship would be Q = m/C/t
8.0 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8
Recommended value
25 or greater
2 PT 1/4
11.4
d 1
10.8
10.9 11.0 11.1 11.2 11.3
11.4
11.5
11.6
11.7
Die
Recommended value
25 or greater
Prepared hole internal thread diameter (d 2 ) ≧ Water hole diameter (d 1 )
3 PT 3/8
14.9
14.2
14.3 14.4 14.5 14.6 14.7 14.8
14.9
15.0
15.1
15.2
■ Simple Test Method for Tapered Internal Threads for JIS Tubing (reference data) ① Unsuitable : U nsuitable for setting up the tap because the prepared hole is too small. ② Dangerous : T he rate of the tap damage occurrence when setting up the tap is extremely high because the prepared hole is small. Setting up the tap requires a high level of skill and technique, and painstaking care, therefore it cannot be recommended because of the danger. ③ Optimum : The prepared hole diameter is the ideal size for tapping. ④ Dangerous : It is not possible to tap a thread that conforms to JIS standards because the prepared hole is large; and the probability of water leakage problems occurring is high. Setting up the tap requires a high level of skill and technique, and painstaking care, therefore it cannot be recommended because of the danger. ⑤ Unsuitable : U nsuitable for setting up the tap because the prepared hole diameter is too large. ※ Sizes at which problems occur at a high frequency rate, even when tapped by a skilled technician exercising painstaking care, have been classified “unsuitable,” although they may fall within the realm of theoretical possibility.
Regarding dimensions of prepared holes for tapered internal threading, JIS recommends “setting prepared hole dimension based on thread seating”, but does not delineate a recommended value for the prepared hole. “Di- mensions of the Prepared Hole for JIS Tube Tapered Internal Threads” are values that MISUMI has investigated and prepared on its own, using plastic mold/cooling–use plug mounting internal thread processing as a point of reference.
■ Tapered External Threads for JIS Tubing −Differences in Appearance Stemming from Processing Methods− (reference data) ① Thread produced by "Rolling" ② Thread produced by "NC lathes" ③ Thread produced by "Dies"
Mold Division, MISUMI
JIS tapered tap
Detailed view of section A
JIS Tapered Tap Blade Length ( ℓ ) (reference from JIS B4446)
Nominal size (No.)
Tapered thread (PT)
x
Regular type (for long threads)
Short–thread type (for short threads)
Section A
6 ± 1.13
1
PT 1/8
19
16.5
7 ± 1.67
2
PT 1/4
28
19.5
※ The above photo uses MISUMI long type LJPS (PT 1/4) Cooling–use Plug. ● Processing of tapered external thread by "dies" is normally used in large variety, small lot production (reference volume: 1 unit and above).
※ The above photo uses MISUMI MSWT (PT 1/4) screw plug.
※ The above photo uses MISUMI standard type JPS (PT 1/4) Cooling–use Plug. ● Processing of tapered external thread by "NC lathes" is normally used in semi mass–production (reference volume:several hundred units and above).
Die
7 ± 1.67
3
PT 3/8
28
21.0
● Processing of tapered external thread by "rolling" is normally used in mass–production (reference volume: several tens of thousand units).
● It is possible to confirm that the amount of thread–cut is proper and that the internal thread is in conformance with JIS stan- dards, when a JIS–standard (B4446) tapered tap is used to achieve a condition in which dimension x is left from point of the maximum diameter of the tap thread ridge. ● Dimension x is the same, regardless of whether a regular or short JIS–type tapered tap is used. Please note that use of a tapered tap with a blade length (ℓ) that does not conform with JIS standards may result in a change in dimension x. For details, please confirm in the user's manual, catalog and other material for the tap you are using. ※ If dimension x is long, the amount of the tap thread–cut will become small. Please note that this will result in a smaller thread–seating area, which may result in water leakage. Note that screwing in the male threaded screw too tightly when mounting the male thread may damage the threads and result in water leakage. ※ If dimension x is short, the amount of the tap thread–cut will become large. Note that this will result in the internal thread becoming wider than JIS standards, which may result in water leakage. ※ Dimension x can be used as a guide for tap thread–cut dimensions but we recommend that for safety, you inspect and test after tapping.
Regarding testing after finish processing of tapered internal threads, JIS recommends "confirmation using a JIS–standard testing gauge (B0253)". “Simple Test Method for Tapered Internal Threads for JIS Tubing” was researched and developed by MISUMI for use as a guideline for simplified testing following mounting internal thread processing of plugs for use with plastic molds and for cooling–use.
● The appearance may differ depending on the method of processing; however, all conform to standards of tapered external thread for JIS tubes. (in accordance with JIS screw gauge testing) Normally, the order of difficulty of hand tightening when mounting is ① → ② → ③ , with ① being comparatively the easiest and ③ being comparatively the most difficult to hand tighten. It can be tightened with Allen wrenches without problem by using the proper torque. E Note that mounting the tapered external thread for tubes by hand tightening alone may lead to water leakage.
Mold Division, MISUMI
1199
1200
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