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Glass Threadless Insulators

The idea of threading glass insulators to secure them to pins was patented in 1865.  Before that time (and for a few years after by companies that did not license this patent) insulators were made without threads and were wedged on the pins by numerous means (Burlap, tar, and other materials were used to help the insulator hold to the pin.).  Threadless insulators are assigned CD numbers from 700-799 and glass block styles from 1000-1014.  There is a large variety of threadless insulators known, and they are all relatively scarce as most were taken out of service over 100 years ago.  The following is an excellent reference on these styles:

A History and Guide to North American Pintype Glass Insulators - John & Carol McDougald

Note:  Click on each insulator for larger pictures and more information!

CD 700 through CD 796 are threadless pintype insulators

CD 700

CD 700.1

CD 701

CD 701.1

CD 701.2

CD 701.6

CD 718

CD 722

CD 723

CD 723.3

CD 723.5

CD 725

CD 726

CD 728

CD 728.5

CD 728.7

CD 729

CD 729.4

CD 729.6

CD 731

CD 731.3

CD 732

CD 732.2

CD 734

CD 734.1

CD 734.5

CD 734.8

CD 735

CD 735.3

CD 736

CD 736.1

CD 736.3

CD 736.4

CD 736.7

CD 737

CD 737.5

CD 737.6

CD 738

CD 739

CD 739.5

CD 740

CD 740.1

CD 740.3

CD 740.4

CD 740.7

CD 740.8

CD 742

CD 742.3

CD 743.1

CD 743.2

CD 743.3

CD 790

CD 1000 through CD 1015 are glass block insulators

CD 1000

CD 1015


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