Proportional dividers are ancient tools, dating back to Roman era, though as late as 1955 some thought they were a Renaissance invention. The Alvin 450 is really handy when making miniatures, like the triangle and engineer’s square above, that I made for Fritz Otto Buchbinder. They allow you to quickly see and measure what a reduction in the actual reduction size would be. Using one is a much more intuitive than having to divide 100ths of an inch into something. But don’t get me started on numeric measuring!
Other uses are to convert a given length of line into equal parts, divide a circle into equal parts, and even generate angles. All of which are useful for bookbinders. The 450 can generate proportions down to 10:1 for lines, and 20 :1 for circles. A regular dividers can do these things, but it takes some set up time.
They make a great addition to my dividers collection. I found them at a flea market, still in a fake leather covered wooden box, with a nifty sliding pin latch, all for $10. They originally sold for $9.75, so they have held their value. New ones are still available, though considerably more costly, having a list price of $216, though commonly found for $132.
Obviously, though, one can never have too many tools. I’m still looking for a used 458 (10 inches long) and a 950 (stainless steel)….