I’ve got a couple of steel backplates, probably EN3. I also made a similar DIN backplate for the Emcomat 8.6 that I had previously from unknown steel

There is a YouTube video by This Old Tony describing the successful making of a steel L0 backplate.

I think that back then the old ladies found CI easier to machine!

From a production cost viewpoint a cast iron backplate blank can be made very close to final size minimising machining time and material turned into chips.

Wonder which is more faff and cost. Casting a simple backplate or chopping a slice off a big round bar.

Possibly not so much of a worry on ME / Home Shop size machines but the D1-5 backplate on my 14″ Taylor chuck is a big lump and that isn’t a particularly big chuck for the larger variety of industrial machines. I’d be unsurprised if cast iron became favoured simply due to being the sensible way for biggish chucks soaking them all from the same material meant that various process optimisations could be developed and exploited.

Clive

Hi, I’ve made a few steel back plates, but the biggest one was a 6″ one. Cast iron ones are quite suitable for most lathes, however they have restrictions on high speeds, as they may not be able to stand the centrifugal forces on them, and so the bigger the diameter, the slower they should go, this also applies to cast iron chucks.

Regards Nick.