# machining a cast flywheel



## McNeillMachine (May 8, 2008)

Hi All,

I guess I should introduce myself, eh? I'm Phil, a mechanical engineer in Boston. I've been interested in machining since I was brought to my grandpa's shop as a little kid (hence the McNeillMachine handle). I do a lot of my own machining at work on a bridgport and clausing 14". I've been lurking here a couple of months, I really like the board.

Right now I'm working on a treadle engine I designed. I bought a couple of 3" flywheels from Tiny Power, and I'm unsure of how to finish them. I need both, so I can't afford to screw up. I have access to a 3 jaw chuck and 5c collets. The main hub and outer rim should be machined, but in what order? Also, there's a lot of flash and pitting on the spokes. I figure on painting this area, but does anyone have a good way of cleaning it up? I'm not afraid of using some elbow grease if thats what it takes.

Thanks,
Phil


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## rake60 (May 8, 2008)

Welcome to HMEM Phil.

When I'm working with a casting, the first step is to determine what area has the most
stock on it. If there is more stock on the hub than the OD, I'll chuck on the OD and rough
the hub. Then chuck on the roughed hub to turn the OD. If the opposite is the case that
procedure reverses. If the available stock is equal it doesn't matter which one is cut first.

Rick


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## tel (May 9, 2008)

As for the spokes, a few files, some emery cloth, a little Bondo for the holes and a lot of the aforementioned elbow grease


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## DickDastardly40 (May 9, 2008)

Hi Phil,

Welcome!

Further to what Rick said as to the machining order, I think I would approach it like this:

Grip on major diameter in 3 jaw, face off, drill & ream hub, flip it round and face the opposite side.

Make threaded mandrell for a collet to suit bore & mount flywheel with nut & washer. Machine OD of flywheel & hub so they are concentric. Reverse job on mandrell and bring OD of opposite hub to match.

Hope this is clear and it helps

Al


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## TinkerJohn (May 9, 2008)

Phil,

Everything so far is right on. I've turned several of Tiny Power flywheels, both in aluminum and brass. They have all been good castings so yours should turn out fine. 

I typically use a Dremel tool for cleaning up the flash on spokes and it works very well. In fact, the last couple of flywheels I've turned I did *all* the clean up first and even painted the final color. Then when turned down you have some really clean lines between the turned area and the casting.

One word of warning: Although this has never happened to me ;D, I had a friend one time tighten the chuck down too much on a small flywheel and broke the casting!

TinkerJohn


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## Divided He ad (May 9, 2008)

Hello Phil, I am afraid I can't give you any direct tips on machining a casting but I can show you some pictures of the type of thing I think Al is describing.
I just finished my new flywheel and posted the pics in the Work in progress section 
http://www.homemodelenginemachinist.com/index.php?topic=1644.15

Hope this helps you to solve your problem?  


Ralph.


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## McNeillMachine (May 10, 2008)

Hi all,


Thanks for all the great feedback. I machined the hub, chucked that up and touched off on the OD - except I forgot to turn down the RPMs from 1500. Boy did that baby sing! All was adjusted, and in due course, it turned out great. Right now I'm going at the spokes with a dremel, trying to polish it all up and get it looking nice. Which leads me to my next question - what kind of paint do you guys reccomend for bronze? Should I do some special type of priming?

Thanks,
Phil


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