Machining Aluminium Bronze

Probably due to the various grades of aluminium bronze I think that advice / tips for machining the stuff can be a bit confusing unless the advice is applied to specific grade/s. (Then of course, the recipient of the advice would need to know the grade of his own material to take advantage of said advice.)

I say this because I have had no problem tapping the stuff I have. I did not experienced any grabbing or any other problem. Given the horror stories I have read about this material I just proceeded with caution with frequent backing out of the tap to prevent swarf jamming. The tapped holes in the steam manifold I pictured earlier in this thread are 1/4" - 40 and I used a good quality little used American HSS "SOSSNER" tap.

Unfortunately I can only relate my experience with the stuff rather than offer advice as I have no idea of the grade I have been machining.

Rik

+1 to Rick Shaw.

I have a project, started years ago that got 'postponed' due to health issues.

The casting was knocked up by a local small foundry and it machined easily in the lathe. So no idea what precise grade and not yet started a whole lot of tappings. I hope to continue shortly, but will take note of the tapping comments.

I turned, bored and single point threaded some aluminium bronze hex bar without any special treatment, should I have been concerned then?

There must be many different grades with different qualities. Back in the 1970s I was involved in tuning model aircraft diesels, and I wanted a highly heat conductive material for contra-pistons. I asked a friend who worked in the BRM F1 team workshops at Bourne, Lincs, and he recommended the aluminium-bronze they used for valve guides. They allowed me to buy a length of bar from their stores, and it was lovely stuff to work with if you treated it like steel but machined it dry. As it was quite a length of one-inch bar I had to buy to make three components each about a quarter of an inch long, I also used it for the internal bits of the fishing reels I used to make in the era, and it was also very easy to tap. Wish I could get some stuff of the same grade now.

We make bushes from it all the time from 20mm ID to 100mm ID. I use coolant and sharp tools, ie the same geometry as Aluminium, but use the surface speed and feed of Stainless steel. The grade we use will work harden like BeCu does , if it rubs and gets too hot. Drilling is the process that will make it work harden the most, centre point sharp drills with the square edge like for brass works very well.

Neil