Popular self spacing frames
In the last half of the 19th century commercial beekeeping made great strides in the U.S.A. with many innovations to help larger scale beekeepers, some of which are still in common use today well over 100 years later. The Hoffman self spacing frame was one of those introductions.
Julius Hoffman was born in October 1838 at Grottkau, Silesia, now named Grodków which is now part of Poland. At the age of 24 in 1862 Julius Hoffman emigrated to London, then four years later to New York, moving again in 1873 to the small village of Fort Plain in NY state. It was here that he is reputed to have built up to 700 colonies.
The Hoffman frame is self spacing because the side bar is the same width as the intended spacing. It is wasted away, so it is not full width for the whole depth. It is most common for one edge to be flat, the other bevelled, to reduce the area of contact, although in some countries I have seen both edges flat.
The popular story is that in 1890 Hoffman was visited by A.I. Root, who saw the frame and subsequently used it in his own apiaries. Although I haven't seen it, there was apparently a letter published in "The Bee Keepers Exchange" magazine Vol 1. No.3 March 1879 that was written by Hoffman's neighbour about the frame. On Page 218 of the March 1st 1880 issue of the British Bee Journal there are drawings of a virtually identical frame, stating that it was part of an exhibit at the Alexandra Palace Show in 1876. It may be that Hoffman never saw the British frame and came up with the same idea, but the closeness of the dates makes me wonder. As with many things in beekeeping people often get credited with the ideas of others. "Hoffman frames" are what they have been known as for a long time, so that's what they will stay.
Hoffman spacing varies, Dadant frames are 38mm wide, British Standard and Langstroth are 35mm. These sizes are what are termed "narrow spacing", which are for normal spacing of brood frames or in super frames for drawing out foundation or producing cut comb.
Although Hoffman frames are the most used I don't like them very much. They use up more wood than is needed, you need another type of spacing if you want to use "wide" and in my experience they get heavily propolised.
There have been several convertor clips designed and marketed to clip on standard frames to make them compatible with wooden Hoffman frames. All those I have seen are plastic and are nailed onto the frame.
I have taken material from several sources for the above. Bearing in mind that historical material may have been distorted, I believe it is as accurate as possible.