How to do a excentric shaft on the lathe???

[mag]

Hey folks, just one question I can´t find a solution for in the web or in my books.

I want to build a small crankshaft for a little engine on my lathe. The problem is, how thick hast the part to be which I have to put under one of the 3 jaws of the chuck. There should be a formula so I could find out how thick it has to be.

the center of the excentric shaft should be 15mm away from the center of the main shaft, i will start with a 45mm round steel.


Thanks in advance for any helpfull hints!

[GRIM]

Hey Mag
To answer your question , USE A 4 JAW CHUCK,
The attach should help explain , doing this in a 3 jaw is dangerous and inaccurate,

Just the same, I have done similar things in the past , it can be done , and usually after many hours of very small cuts you finish up having to re make the con rod due to inaccuracies in the crank

Good luck and let us know how you get on

[mag]

Thank you very much! I´ll take your advice and see how to atach the 4jaw chuck on my lathe, better safe then sorry.

Many Thank!

Could you explain how you got the measurement? Any straight formula for that?

Thanks, mag

[GRIM]

No magic formulas , Autocad ,
Beware , with a 4JAW you will be looking for a total excentric displacement of 30mm , which should be the stroke of your engine , given the 15mm between centres.
good luck