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What Lathe Chuck Backplate

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Laurentic:
Despite being a lifelong member of the "Deep Pockets and Short Arms" club, I have just treated my 60 or so year old lathe to a new self-centring 3 jaw chuck.  That's new out the box new, not just new to me, so proper new!  The old 3 jaw was once a quality item in all probability, but now the jaws are a rattling good fit and if I can get a part to run ro within a 5 thou run-out then it's a very good day; enough was enough.

Now I was intending to re-use the old 3 jaw backplate, after all, it just needed 5mm off the location spigot diameter and three new bolt holes drilling and the job's a good 'un.  Except that it's either hardened or case hardened steel.  It just laughed at my HSS toolbit and promptly flattened the tip without taking a scratch itself.  I don't have carbide tooling, or know if that would work on hardened surfaces.

So I feel I need to machine up a new one.

The choices for buying I have are:
an unmachined casting in cast iron, or, from my usual metals supplier, either a billet of
cast iron, or
EN1A bright steel, or
EN3 black steel.

The unmachined casting is available at a reasonable (in todays terms) price.
The billet of CI would be a fair bit more, the
EN1A bright steel a couple of quid less, and the
EN3 black steel a few quid less still.
But the killer for any billet is the supplier would charge nearly £14 for postage due to its weight, whereas with the casting the delivery cost is built into the price (they call it delivery free!).

Now machining the casting should not be too much of a problem providing the surface can be machined off without difficulty, but it is a messy, dirty, job from memory, CI dust everywhere.  The same would apply to the CI billet except the skin would not be a problem,  The EN1A machines beautifully, not sure of the EN3, how that would machine, had very little experience of it.

Given that I have just had my second cataract op on my eyes, so both eyes now done, and for the first time in years my vision is bright, sharp and very clear, I need to stay away from dusty conditions as much as possible.  So my choice of material is very much my decision on how I manage the machining, and obviously the financial aspects are my decision alone, but i am interested to know:

What does the Team think would be the best material from which to machine the required backplate if it were their lathe chuck backplate?  Thinking in terms of strength and rigidity and machinability type issues here rather than cost. :old:

Many thanks in advance for any opinions offered.  :cheers:

Chris

Jo:
I would give it 4 weeks post op before you make dust/swarf again...


Buy yourself one of the backplate castings: They are much nicer to machine (normally) and CI is easier on the lathe nose. If you are worried about the CI dust set up the workshop vac under the lathe tool to slurp up the dust as it is machined off.

Jo

uuu:
I like cast iron, and have made backplates for my lathe from it.  If you're going for a casting, you may want to invest in some carbide tooling, either brazed tip or inserts.  The skin of a casting can be quite abrasive on HSS tooling.

Wilf

Edit - I have found plain backplates available - so the lathe side is already done and only the chuck side needs machining.  Also see this article, which may be useful:  https://www.arceurotrade.co.uk/reviews/Backplate%20Fitting%20-%20MEW%20141.pdf

Jasonb:
I don't know what your lathe is but if the option of a part machined backplate is available that would also be worth considering as they just need the face skimming and the register cutting.

I've machined the cast backplates as well as making from a slice of steel and there is not much between the two. If you are getting a lot of dust from cast iron you need to look at your tools as there should be very little, look at the paper here hardly a trace of dust, just chips.

http://www.youtube.com/watch?v=z57PJPN6WzQ

Same when facing

http://www.youtube.com/watch?v=gwB9PeUSMpI

And some EN3 for comparrison

http://www.youtube.com/watch?v=vT4-tZeDxSY

john mills:
what size is the chuck and what is the lathe
what type of spindle is it screwed  if back plates are available that would be good
a vacum could control dest  try to take bigger cuts producing bigger chips
if you use steel i would prefer the black bar
a cast back plate  would  good

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