Holding a disc to jaws / faceplate

Hi,
I am pretty new at machining.
How can I attach a disc that is larger than my jaws and machine all
sides without putting a hole in it?
An example would be a 200mm dia disc, 1/2" thick made from mild steel.
Reply to
greg
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What about: make a holder that you grip in the chuck. Use grubs around the periphery to clamp the work into the holder.
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Reply to
Rob
Chuck a short bar , as big as will fit. Face it off true, then superglue your part to the bar. It helps to have a few grooves in the face of the bar in the chuck to allow a bit of air access to the glue/part interface.
Remove with heat from a propane torch. Don't heat it enough to smoke the superglue, and if you do, don't breathe the fumes. It takes around 350 to 450 degrees F to get the bond to break.
Clean part with acetone.
Take light cuts with a sharp tool.
Cheers Trevor Jones
Reply to
Trevor Jones
Clamp it radially with 3 or 4 set screws (see dwg above) or even clamp tabs with the clamp bolts in-line with the lathe axis.
Strt by welding some 25mm + bar stock to some plate and build on it from there.
Reply to
Rob
Depending on desired finish and accuracy, you could maybe do half the edge thickness at a time, then flip the disc over to do the other half.
Reply to
Jordan
I made something that goes in the tailstock that is somewhat like a live center, except instead of a 60 degree point it has a flat disk. I used a roller bearing for a car front wheel. So I can put a mandrel with a disk in the chuck and this thing in the tailstock and clamp the two together to machine the edges of disks. A piece of rubber or double sided tape on the disk clamped in the chuck improves the friction.
The bit that goes in the tailstock also has some alternate parts so it can work as a pipe center too.
Dan
Reply to
dcaster
Mount a large diameter chunk of something in the chuck and face it off, and turn the OD to slightly less than the diameter of the workpiece, if necessary. Make sure one face of the workpiece is completely flat. Use wax, superglue, double-stick tape or whatever you have to attach the disc to the mandrel you just made. Now, you have the other face and the OD of the disc completely exposed for facing and turning. Obviously you need to go easy on it of it will come off the mandrel.
Another method is to use some kind of "pusher" attached to a live center to press the disc against the mandrel. This won't allow you to face all the way to the center, though.
Jon
Reply to
Jon Elson
Will using superglue on a very heavy disc that is only rough cut really hold it on there?
Reply to
gdenehy
It can. You need to face one side of the thing any way you can to get it flat, first. If it is so big that you can't get the jaws around it, then you might need to use a 4-jaw and reverse the jaws. Once one face is flat, you can then glue it to the mandrel. it works best if the mandrel is at least 3/4 the diameter of the workpiece. You can also use a faced piece of thick-walled pipe as a mandrel.
And, of course, you can't take heavy interrupted cuts when mounting work like this. But, if you want to face and turn the OD of a part in one mounting, you have to make compromises. The only other way to do it is to mount a thicker piece in a chuck, face it, turn OD, and then part it off.
Jon
Reply to
Jon Elson

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