I totally agree that a blade lift on the return stroke would be the ideal, and most industrial machines have this as well as a dashpot feed but these are heavily built affairs where such items are required. For the light amateur workshop machine I am not sure if this is really necessary, and a compromise can be achieved through geometry. As an example the machine I built http://www.homemadetools.net/forum/h...6648#post84095
does not have a start capacitor fitted and as such sometimes starts in reverse, if I run it like this it will hardly cut at all. Indicating to me that the geometry is working against it and not with it. As built the cutting stroke is a pull stroke with the motor arm rotating downwards and this works fine. In use the blade frame can be seen to lift slightly on the return as long as to much weight has not been added. I think what is happening is similar to using a hand hacksaw in that a reduced pressure is used on the back stroke rather than lifting the blade.
I freely admit that this was not factored in at the design stage and simply worked out that way (we can get lucky sometimes). I use standard by-flex blades which are cheap and plentiful and they seem to last a reasonable time and I use it a lot for quite large lumps of steel.
If I wanted something with a better performance I would go for a home built horizontal band saw for metal which gets rid of the problem.
I look forward to any ideas to enhance my machine that are not to complicated.