Mold Components Pages 51 to 64 How to Machine and Seal Metric Cooling Line Threads By Brenda Clark A common challenge for North American mold designers and mold builders is ind-ing good information on how to seal a metric straight cooling plug or itting. In North America, shops more widely use national pipe thread (NPT) itting threads, so they are less familiar with British standard pipe parallel (BSPP) straight thread pipe plug use. Here we will focus on metric thread ittings for pipe threads (G-thread or BSPP and R-thread or BSPT), and the itting and sealing speciically. Machining Tips The most critical aspect of machining for straight-type cooling plugs and ittings is the cooling line core diameter, which should never exceed the minimum thread core ID. Adhering to this rule while also using threading compound (for example, pipe tape) allows the plug or itting to seal. Some cooling line plugs include a copper sealing washer or a recommenda-BSPP (G) male and female parallel thread ID/OD (Fig. 1, top), BSPT (R) male taper thread OD/ tion to use an o-ring for positive sealing. female parallel thread ID (Fig. 2, bottom). Each pipe designation identiies a fuel type, not a thread classiication. For example, the “F” in NPTF is for fuel. NPTF threads generally screwed into the female parallel (G) threads, but (R) BSPT do not require additional Teflon tape or sealant. They seal off male ittings can be screwed into the female parallel (G) and with the tapered thread. The “G” in BSPP and the “R” in BSPT female tapered (R) threads. refer to gas parallel and gas taper, and both require additional After selecting your thread type for the itting and cool-sealing tape or application of a sealant to seal off. ing lines, calculate the minor cooling line and tap drill NPT and BSPP threads are not compatible. The NPT thread diameters. These two measurements ensure that you suc-has a 60-degree angle with flattened peaks and valleys. A BSP cessfully assemble the cooling line plug or itting to seal thread has a 55-degree angle with rounded peaks and valleys. off. If the main cooling line is larger than the minor cooling You should never mate a BSP thread and an NPT thread, as the line and tap drill diameters, you will not achieve seal off incompatibility prevents reaching the required pressure ratings no matter how much sealing tape you add. Take caution and will damage threads. when drilling the cooling lines — even before machining A BSPP thread is parallel on the male itting and female thread the female thread — so enough steel remains for the entire in the cooling line (G). A BSPT thread is tapered on the male thread detail. itting (R) and the female thread in the cooling line is either FOR MORE INFORMATION tapered or parallel. This means you can machine the ID or a female thread tapered or parallel on the cooling lines for (R) only. HASCO America Inc. / 828-650-2619 / hasco.com Brenda Clark, Engineering Manager Pay special attention to the itting type you are using on the cooling line. For example, (G) BSPP male ittings can only be 6 64 M MoldMaking g Technology y — — JU JULY 2022 Images courtesy of Hasco America Inc.