Bronze Castings

Here is a bronze casting in the form of a rectangular solid bar, and a reel foot made from this material.

Bronze alloy C954 is supplied as a casting, made by the “continuous casting” method. The cast bar is quite uniform and is oversize; this 1/4 x 3 inch nominal bar measures 0.34 x 3.07. That is so it will clean up to at least 0.25 x 3.00. In my experience, it would have clean surfaces at 0.32 x 3.05. A bar of nominal 2 – 1/2 width is easily wide enough to make a 2.50 long reel foot.

C954 machines well, having a machineability index of 70 (ref. brass C360 at 100). But there is a problem using it for reel parts: it has some porosity. Below are the outcomes of starting six reel feet. Three of them are useable and have no surface flaws, once I sand them. But three others have small voids that appeared during machining. The voids are small, about 1/16 inch diameter, but are definite cosmetic flaws.

What came to my attention is that all the voids are very close to the center of the bar. I believe that the voids form as the metals solidifies after casting, and that the center of the bar is the location of maximum material stress. So here is the solution for future reel feet: buy C954 with nominal 1/4 x 1-1/2 section and orient the blanks longitudinally rather than across. A 2.6 inch cutoff will then provide two reel feet (which finish at 0.525 wide) and a bit of waste from the center that has possible voids.

Common metals like brass C360 and aluminum 6061 are made into bar stock by extrusion; I have never encountered a void in an extrusion. A sensible person would probably be making reel feet from C360 instead of cast bronze.

For the front end ring and back end plate of my “bronze frame reel”, I use bronze alloy C544, which is made by extrusion and has no voids. It has a machineability index of 80. I would like to use it for the feet as well, but it is only made as round rod stock, so is a very inconvenient starting point for a foot. Alloy C932 would be much easier for a home shop machinist to source, and comes as round rod. But these rods are made by casting, and I would expect to see voids. Not a problem for front end rings, but fatal for making rear end plates.

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