Machining a flywheel

[RonLyke]

OK, Here's where I show my ignorance.

When machining a simple flywheel (basically a disk), after machining the first side, and reversing the piece in the 3 jaw chuck, how do I set it up so the second side will be parallel with the first side (assuming the jaws are deeper than the thickness of the stock)?

This would probably be obvious to a smart person.

 

[rac37]

I will often use a parallel or two behind the work piece to get it square to the chuck. Just be sure to remove them before starting. Works for me most of the time.
Bob

 

[Boot]

If your chuck has t-slots bolt the Paras on to keep them from launching. If not like Rac37 says slip them out from under it. Some jobs you will find are able to rest on top of the jaws which should be parallel and they can hold the part on either the o.d. or i.d.. Don't forget you can reverse the jaws to make some setups also and then grip the part accordingly. Boot

 

[Fabrickator]

You can find "close" center of any disk, bar or square stock using the crisscross/90* line method. Drill a hole smaller than the final plans call for. Then run a bolt through and tap into an appropriate size bar stock (depending on the weight of the piece) using the same method. Chuck the bar stock and back the disk into the chuck for additional support. This also works good in the event that your jaws wont go large enough. Once chucked, start by running at a very low speed until you get the OD rough cut to try and establish some balance, or the face, whichever is worst. Once you get one face done, flip it and do the other and then rough finish the OD. After that, if it's larger than your jaws-turn a hub to chuck on and lose the bar stock.

I use this method a lot for this type of task and also for truing up large chunks of logs for bowl turning.

Rick

 

[GWRdriver]

Your chuck jaw flats should be plenty accurate enough to hold the wheel rim close enough that you can't see any runout, but if the jaws are not coplanar, or that's not accurate enough for you, there is another way. If there is enough space between the back of the wheel and the chuck to get the wiggly bit of a DTI (dial test indicator, or just indicator) behind the wheel you can indicate (square) the back of the wheel. This can be done by snugging the chuck jaws a weensy bit and tapping the face of the wheel lightly. The DTI will need to be backed out every 1/4 revolution to allow the chuck jaw to go past.

 

[RonLyke]

Thanks for all the suggestions. No T slots here.
I did find something that helped, quite by accident. I have 2 lathes---a South Bend 10L, and a SB 9a. Mostly, I use the 10L, but the 9a has a chuck--a 3 jaw Buck Adjust Tru, which a previous owner butchered (or so I thought). The face of the jaws were turned about 3/16" deep, with a radius just right for holding a 1-1/2" flywheel. I guess all my projects will have 1-1/2" flywheels.

 

[Chiptosser]

I have glued pieces of flat stock to the jaws, phenolic material, wood ect.
you can make a light cut on these pieces to make sure that they are the same height.
You can make spacers that saddle the jaws , basically a U shape, an add a set screw to lock them on the jaw.

 

[TimTaylor]

What are you starting with for raw material?

1. If it's a piece of round bar stock, start with a piece long enough that it sticks out of the chuck an inch or so more than the final width of the flywheel.

2. Next step is to face it and turn the OD to desired final diameter.

3. Without removing it from the chuck, use a drill chuck in the tailstock to drill the center hole, which will be co-linear with the rotational center.

4. Part it off to the desired width.

You can then bolt it to a piece of bar stock as Rick suggested to finish the other side, but before you do, face the piece of bar stock so that it is square to the rotational center.

You can use this procedure up to the max diameter your chuck will hold.

If you're starting with a casting it's a little different - depends on how consistent the OD of the casting is, but it's the same general idea.

For a part larger in diameter than your chuck will hold, your best bet is to find the center as Rick described and go from there......

 

[GailInNM]

On your 3 jaw Buck Adjust Tru you can slip in some soft aluminum strips of about 1/32 or 3/64 thick between the jaws and the work for doing parts greater than the 1-1/2 inch diameter. The aluminum strip will deform and prevent the edges of the jaws from marring the work.
Gail in NM

 

[RonLyke]

Great suggestions! Thanks very much.

 

[gus]

Here is how I did the Webster engine 4'' flywheel with my very small lathe using a 4'' three jaw chuck.

 

[deverett]

Another way for machining small flywheels is to use a super glue chuck.

Machine the first face. Then get a piece of ali bar of larger diameter than your work. Face one end and cut some shallow (5 thou or so) concentric grooves.

Use some super glue and stick the good face onto the ali. It doesn't have to be concentric. Face the second side of the flywheel.

If you need to work on the diameter, after machining the first face drill/ream a hole the same size as the crankshaft. Make a tapered mandrel (just a few file strokes with the embryo mandrel spinning in the chuck to give a very fine taper ) and mount the flywheel onto this. Again you can use super glue if the hold is not too good. Before working on the diameter, check that the face of the flywheel is running true with a DTI.

The super glue joint can be broken with gentle heat.

Your new super glue chuck can be used over and over. Each time, just face it true and cut some more grooves if necessary.

Dave
The Emerald Isle