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Spools & Mine Insulators
Another area I like to specialize in is Hemingray spools. Spool insulators came in a variety of different styles and sizes, and can be grouped into four main categories: mine insulators, break knob spools, dead-end spools, and special usage spools. The one thing almost all spools have in common is they have a hole all the way through the insulator. The hole can either be threaded or unthreaded. (Some people mistakenly refer to these as threadless, but that's an entirely different category of insulators that predate these by several decades.)
It's important to note that glass spools were made by several other glass companies as well, including Brookfield and KCGW (King City Glass Works). With unembossed spools, it's often difficult to tell who manufactured them.
You can click on any of the insulators below to get more information on that particular style.
As you can probably guess, mine insulators (also sometimes called Feeder Wire insulators) were specially made for mining applications, where one or more lines for electricity were brought into a mine shaft, either on the ceiling or on the side of the shaft. A special, hollow pin was often used in tandem, which would channel and drain the water through the hole in the middle of the insulator and help prevent it from shorting out the circuit.
Naturally, these insulators saw very rough service and are frequently found with damage. It's a rare treat to find one in mint condition!
CD 185
The CD 185 is probably the best known type of mine insulator. In fact, some specimens made by Hemingray are actually embossed "mine insulator", so there is no doubt as to what they were used for! A special, hollow pin was often used in tandem with these, which would channel and drain the water through the hole in the middle of the insulator and help prevent it from shorting out the circuit.
Hemingray made these with a variety of different embossings, including "Hemingray", "Jeffrey Mfg. Co.", "Mine Insulator", and possibly even unembossed ones (supposedly one exists, but I have yet to see it in person to determine if it's a Hemingray product or not).
CD 1025
The CD 1025 is a unique design and only a handful are currently known in the hobby. While they're only embossed with "Patent Applied For" (both above and below the wire groove), specimens have been dug from the Hemingray dump so we know for sure that Hemingray manufactured these. The special feature of this spool is a slotted/keyed pinhole where thei insulator would slide into place, be rotated 90 degrees, and the insulator would be locked into place.
Break knob spools are typically smaller than a regular insulator, and were more intended for low voltage, telephony and house wiring applications (though several styles have been found used in mines as well, so they could technically be called mine insulators!)
A third category of spools is referred to as "dead-end" spools, as they were often used at the end of a line for secondary power applications. Hemingray made these styles mainly during the 1900s-1940s.
