B
Bogstandard
Guest
Bar material in the larger sizes does get slightly expensive if you buy from a merchant but if you have some thick plate it is just as easy to make a flywheel from that.
First off mark up the size you require and centre drill the centre point, make sure your centre drill hole isn't larger than the hole you need in the centre.
Then just rough cut off, you don't need to take it this close but it will mean more time turning it down, and stick some masking tape on the back to cover the whole area, doesn't need to be neat.
Now chuck a piece of bar in your three jaw that makes the outside edges of the jaws just a bit smaller than the flywheel size, but have it sitting inside the jaws.
This bit now looks a little unsteady, but rest assured that it is safe. You have to have a rotating centre to do it this way, a solid centre just will not work. Trap the plate between the chuck jaws and the rotating centre, leaving enough room for the saddle to traverse the cutter across the outside edge. This is called friction turning and can be used for all sorts of things like cutting discs out of perspex etc, but the centre is mounted in a slightly different way. Take cuts across the outside edge of about 10 to 15 thou, don't worry if you put on too heavy a cut, all that will happen is the plate will stop turning, just take the cut off, and come in with a shallower one. I have done lapping plates up to 2 feet diameter using this method.
After a few minutes you should end up with something like this. Don't turn to finished size, leave a little bit on for final finishing and trueing up.
Deburr the edges.
Put your outside jaws on the chuck and mount up the plate into it and drill and bore or ream your finished size hole.
The next bit is how to get everything running true to the bore so you don't end up with a 'wobbly' flywheel. Put your normal jaws back on your chuck and chuck a piece of bar sticking out of the chuck by the thickness of the flywheel plus about 1/4". Turn this bar down until it is a very close fit for the flywheel centre hole, and about 1/8" shorter than the thickness. drill and tap the end for a bolt and washer to clamp the flywheel onto it. All processes on the flywheel from now on are done using this mandrel, so DO NOT remove it from the chuck until everything is completed.
This is where you find out just how far your chuck is out of kilter. Put a spot of superglue on the machined part of the mandrel at the chuck end and put your flywheel onto the mandrel and lock it on with the screw and washer. Turn the outside edge to size. Then face down the front until you nearly reach the locating screw and washer. Turn off the machine without taking off the cut and remove the screw and washer, turn back on and carry on with the cut until the centre is reached, the superglue should hold it well enough for light cuts. Apply a bit of heat from a blowlamp and this should break the superglue seal and allow you to remove the disc from the mandrel. Borrow your friends best woodcutting chisel and use it for scraping off the old superglue, remount the disc the other way round using superglue again, and face this side to the thickness required but don't take out the screw until thickness is reached. The boss that is left in the middle is now machined away very gently using the superglue only to hold the disc in place. The pic here shows me machining the face with just supeglue holding it.
Reinsert the screw and washer and do all your decorative bits to the flywheel.
Recess
Concentric circles
The mandrel can now be removed from the chuck, but can be reused when you come to the polishing stage as this isn't critical on concentricity.
All this was done in less than an hour.
John
First off mark up the size you require and centre drill the centre point, make sure your centre drill hole isn't larger than the hole you need in the centre.
Then just rough cut off, you don't need to take it this close but it will mean more time turning it down, and stick some masking tape on the back to cover the whole area, doesn't need to be neat.
Now chuck a piece of bar in your three jaw that makes the outside edges of the jaws just a bit smaller than the flywheel size, but have it sitting inside the jaws.
This bit now looks a little unsteady, but rest assured that it is safe. You have to have a rotating centre to do it this way, a solid centre just will not work. Trap the plate between the chuck jaws and the rotating centre, leaving enough room for the saddle to traverse the cutter across the outside edge. This is called friction turning and can be used for all sorts of things like cutting discs out of perspex etc, but the centre is mounted in a slightly different way. Take cuts across the outside edge of about 10 to 15 thou, don't worry if you put on too heavy a cut, all that will happen is the plate will stop turning, just take the cut off, and come in with a shallower one. I have done lapping plates up to 2 feet diameter using this method.
After a few minutes you should end up with something like this. Don't turn to finished size, leave a little bit on for final finishing and trueing up.
Deburr the edges.
Put your outside jaws on the chuck and mount up the plate into it and drill and bore or ream your finished size hole.
The next bit is how to get everything running true to the bore so you don't end up with a 'wobbly' flywheel. Put your normal jaws back on your chuck and chuck a piece of bar sticking out of the chuck by the thickness of the flywheel plus about 1/4". Turn this bar down until it is a very close fit for the flywheel centre hole, and about 1/8" shorter than the thickness. drill and tap the end for a bolt and washer to clamp the flywheel onto it. All processes on the flywheel from now on are done using this mandrel, so DO NOT remove it from the chuck until everything is completed.
This is where you find out just how far your chuck is out of kilter. Put a spot of superglue on the machined part of the mandrel at the chuck end and put your flywheel onto the mandrel and lock it on with the screw and washer. Turn the outside edge to size. Then face down the front until you nearly reach the locating screw and washer. Turn off the machine without taking off the cut and remove the screw and washer, turn back on and carry on with the cut until the centre is reached, the superglue should hold it well enough for light cuts. Apply a bit of heat from a blowlamp and this should break the superglue seal and allow you to remove the disc from the mandrel. Borrow your friends best woodcutting chisel and use it for scraping off the old superglue, remount the disc the other way round using superglue again, and face this side to the thickness required but don't take out the screw until thickness is reached. The boss that is left in the middle is now machined away very gently using the superglue only to hold the disc in place. The pic here shows me machining the face with just supeglue holding it.
Reinsert the screw and washer and do all your decorative bits to the flywheel.
Recess
Concentric circles
The mandrel can now be removed from the chuck, but can be reused when you come to the polishing stage as this isn't critical on concentricity.
All this was done in less than an hour.
John
