Does anyone have a method of cutting the center out of a magneto flywheel for using it as part of a 2 part prop hub that won't ruin the fit on the crankshaft? I tried a few things like a hole saw without any luck, my flywheel is 5/8" thick where I need to cut thru it. Is it possible to maybe make a tapered mandrel to mount it in a lathe? The engine is an older Stihl about a 25cc. The part I am trying to save resembles a larger Supertiger prop drive which I want to use for my magnet mount ring.
If there is an easy way to do this, I'll try it. There are already two threaded holes in it to mount the second half of the prop drive which I can machine on the lathe. Any ideas? I can provide a picture if needed.

Thanks for any ideas you may have.
John

I believe that your best option is to reproduce the shaft in the lathe, install the flywheel on it (without removing the mandrel) and then cut it.

If too cumbersome to do all on the lathe, you could do a rough cut above the diameter that you need by any means (multiple holes, hacksaw, etc.)

Proper centering is the key for what you want to achieve.

Pictures always help

Reproducing the tapered shaft and mounting the flywheel to it is probably my best option in this case. I will post a picture or two today of the flywheel so you can see why I want to preserve as much of the center as possible. In my opinion, it will give plenty of support and provide a mounting method. Resembling the largish prop driver from a Supertiger. This is the end result I want to accomplish. It has two webs inside of it which can be drilled for the magnet, or I can do the outer diameter like all commercially made hubs. I hope this works. I have a semi scale rough drawing of what I want it to look like which I will post also.

John

I have done this numerous times and it works fine. I usually just cut the center out with a hole saw in the drill press however, and then true the center piece up in the lathe.

AV8TOR

If you can reproduce the shaft,then you can make the hub you need, why go through all the other work?

Maybe I'm not understanding the question. If so disregard.

Make a prop hub and the nut that retains the flywheel the same piece, like a G-38. You will need a lathe to do this kind of work. Otherwise it will never be in balance, except by luck.

Take any crankshaft with the taper you need to mount flywheel (in lathe) and use a hacksaw and cut it off and use the stub shaft you have now to mount the shaft and the flywheel in lathe. Use a cut-off tool and cut the outsidepart of the flywheel off ...cutting from face. Then turn down the edge or outside dia of the hub you are making too the size you want. I got a collection of stub shafts with various tapers...just to place flywheels on too turn down to make a hub. Capt,n

Captinjohn, I will have to make a stubshaft, since I don't have any cranks that aren't being used. I haven't measured the taper yet but it looks different from Ryobi's and Macs. The shaft is very short with very few metric threads on it.
Haven't had a chance to setup my lathe since we moved last year but now that I am retired, hoping to get all setup in the coming weeks. Been busy building ignitions and advance boards... Must have 30 or so sitting on my bench ready for wires and testing. The design works well in my planes so I'm not building anymore till these are sent out.

Do you make alot of prop hubs? I had bought a 20 foot length of 1-3/4" hex aluminum about 5 years ago and only have 4 feet left. Did alot of hubs and parts for helicopters I built. Using a harbor freight lathe and small milling machine I built from a Taig Microlathe. I'd like to make a few of the stubshafts for the rest of the engines I have in my garage. A few Echo's, Ryobi's, but mostly Macs. Have to trash the plastic and junk metal to make room for the new planes I'm building this winter.

John

Go to a few small engine repair shops and look for a dead engine for a crank. They throw they away or stock pile them and sell em cheap to a metal buyer. It is a lot faster and very easy. Make good friends with the shop owners (buy them a meal) and they will give you all kinds of deals...including FREE!!!! Capt,n

Also use av8tor,s Idea ....and use a circle saw to cut the hub...then true it in the Lathe.

Hope I can post a few pics of the flywheels I want to use the centers from. [img][/img]

It depends on the construction of the flywheel too. If any steel intrudes on the area you want to cut out, the hole saw won't cut it. Been there, tried that...

AV8TOR

Av8tor, i will attempt again to put some pics here of what the flywheels look like..first one is a 5/16" straight thru hole so it's not a problem putting it on a mandrel and chucking on that in the lathe.. the second one has the taper..

John