Newbie lathe question - turning a disk


I have a disk of aluminium alloy, thickness 8 mm, OD approx 70 mm, with
a 25 mm hole in the centre. I need to turn this down to OD 50mm.
Can anyone suggest a good way to do this in a mini lathe (a Sieg C2A),
please?
(In searching I found this

which may not be the way to do it but looked interesting anyway)
Reply to
Dave A
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I don't know the C2A, but on my C3 the inmost section of the three-jaw will fit into a 25mm hole... surely it can't be that easy?
-- Peter Fairbrother
Reply to
Peter Fairbrother
You could do it that way but you've got a lot of metal to remove.
I would mount a piece of say 2" bar in the lathe chuck, turn it down to give a short spigot 25mm diameter to a good fit in your centre hole and say 6mm long, then drill and tap for a bolt. Without removing it from the chuck, mount the work and hold it in place with a bolt and a big washer then turn away - guaranteed concentricity of rim and hole and a good solid grip.
Reply to
Norman Billingham
Will the inside jaws go in the 25mm hole?
Or turn up a mandrel from say 30mm or larger stock with a 25mm dia section 7.5mm long, drill and tap the centre, bolt and washer to hold the disk on and go for it.
25mm bolt and a nut.
Depends what you have lying around and how accurate you need it to be.
Andy
Reply to
news
In article , Norman Billingham writes
A much posher version of Norman's suggestion, for more than a one-off- task, might be:
formatting link
Much more work obviously, but you have made a tool for keeps. looks like a grand item for wheels and similar in the small workshop. And good enough precision for a Clockmaker it seems......
John
Reply to
JC Morrice
I would remove the chuck jaws completely and use a piece of rubber sheet between the chuck body and the work to provide the friction and plenty of support.
John
Reply to
John

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