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Model Forum / General / Models / May 2010Newbie 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 <http://www.machinistblog.com/use-friction-turning-to-make-thin-disks-and-flywhee ls-on-the-lathe/> which may not be the way to do it but looked interesting anyway)  SignatureDave > 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. [quoted text clipped - 5 lines] > <http://www.machinistblog.com/use-friction-turning-to-make-thin-disks-and-flywhee ls-on-the-lathe/> > which may not be the way to do it but looked interesting anyway) 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 >> 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? > 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 Yes, it is! They will go down to around 18mm. Thanks for prompting me to check! SignatureDave >>> 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. [quoted text clipped - 9 lines] > Yes, it is! They will go down to around 18mm. Thanks for prompting me to > check! Sorry: I meant 23mm. About 1mm clearance all round in the case of my disk. SignatureDave >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. [quoted text clipped - 5 lines] > <http://www.machinistblog.com/use-friction-turning-to-make-thin-disks-and-flywhee ls-on-the-lathe/> > which may not be the way to do it but looked interesting anyway) 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. >>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. [quoted text clipped - 14 lines] >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. A much posher version of Norman's suggestion, for more than a one-off- task, might be: http://www.davewestclocks.co.uk/Wheel%20holding%20device.htm 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 SignatureJC Morrice john@pentode.demon.co.uk 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 On 22 May, 16:21, Dave A <n...@themagicspamtractortrap.freeserve.co.uk> wrote: > 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. [quoted text clipped - 8 lines] > -- > Dave 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 |
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