North American 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

Thanks to Dario Dimare sharing his extensive and excellent collection of threadless insulators for photographs, this section has been significnatly updated with many new CDs and variations. Also note that Dario owns the assignments for new CDs as he has taken over for N.R. Woodward for this important responsibility.

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

CD 700 through CD 702 threadless "egg" style insulators

CD 700 CD 700 CD 701 CD 701.2 CD 701.5 CD 701.6 CD 701.8 CD 718

CD 720 through CD 725 are "Wade" style insulators designed to fit within a protective wood cover.

CD 721 CD 722 CD 723 CD 723.3 CD 723.5 CD_723.6 CD 724 CD 724.3 CD 725

CD 726 through CD 728 are later styles with a straight skirt

CD 726 CD 727 CD 728 CD 728.2 CD 728.4 CD 728.5 CD 728.7 CD 728.8

CD 729 through CD 733 are later styles with a concave skirt

CD 729 CD 729.3 CD 729.4 CD 729.6 CD 731 CD 731.2 CD 731.3 CD 732 CD 732.2 CD 732.4

CD 734 through CD 735 are hat style insulators with no bottom wire ridge

CD 734 CD 734.1 CD 734.5 CD 734.8 CD 735 CD 735.3 CD 735.6 CD 735.7

CD 736 through CD 739 are hat style insulators with two wire ridges

CD 736 CD 736.1 CD 736.3 CD 736.4 CD 736.5 CD 736.7

CD 737 CD 737.5 CD 737.6 CD 737.9 CD 738.5 CD 739 CD 739.2 CD 739.5

CD 740 through CD 742 are round dome hat style insulators with a single wire ridge

CD 740 CD 740.1 CD 740.3 CD 740.4 CD 740.6 CD 740.7 CD 740.8 CD 742 CD 742.3

CD 743 family are bee hive styles from Canada

CD 743.1 CD 743.2 CD 743.3

CD 780 to CD 799 are unique styles

CD 780 CD 785 CD 788 CD 790 CD 791

CD 1000 through CD 1015 are glass block insulators

CD 1000 CD 1015

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