There are lots of pictures here so please wait while they load.
First, chuck a piece of stainless steel that is bigger than the valve that you want to make. Turn this down to the size of the valve stem and cut the notch for the keepers. (below left)
This (above right) is a close-up of the notch for the keepers. You can see that I beveled the bottom of the notch, I did that mostly for ease of construction. It helped me to get the cutter in on an angle.
This (above) is a view of the keepers. They are laying next to a quarter for size comparison. The angles used on the keepers and spring seat are 60 deg.(a standard center drill).
Then turn down another section. I did the stem in sections because I don't have a follow rest. The short sections will not flex too much. (pic below)
Then turn down to the seat, cut the seat on a 45 deg. angle. (pic below left)
This is a closeup of the seat.(above right) The seat and the stem have not been blended together yet.
Next, blend the seat and the stem together with a rounding cutter. (pic below left)
This close up view (pic above right) shows the stem and seat after blending together.
Then part off the valve, chuck the stem, and cut the face and you have a valve!
This is how I made the valves for my engine. I made the intake and exaust the same size. I know that the intake is normally a bigger valve, but I didn't think that it was worth all that worry. I don't know how much bigger it should be. I am making this engine just for the fun and experiance. Once it is made, I don't have a use for it. I just want it to run!
All work was done on a Smithy 1220XL by someone (me) who doesn't know anything about machining or the engines he is trying to make.
The specifications of the valves shown are (in inches):
Stem Dia:.......... .1875"
Notch Dia.......... .140"
Face Dia........... .430"
Overall Length.... 2.030"
You may have noticed that the valve stem is rather large compared with the rest of the valve. This is because I don't know a good way to turn such a thin shank and keep it straight. It seemed to me that if it was larger that it would be stronger and easier to make. On the next engine that I build I plan to make them smaller.