Trying different fly-cutter designs

Work in progress

Shop made Flycutters, made on the mini-lathe

Not only making tooling is for me a pleasure and a good practice exercise, as I also like to try different things to see what works better. Flycutters can be very cheap, but they are also very easy to make. These ones were entirely made on the lathe. Milling work was made with compound mounted vertically, with a angle plate, on the mini-lathe cross slide.

This plan, available at GrizzHFMinimill group, was the starting reference to make the larger one on right. I haven't followed strictly plans as I use metric rather than inch measures. Made it with 35mm diameter for 8mm toolbit and with 12mm shank. Shank is 35mm long to use with ER collets.

The reason to choose this plan to start with was the 10 degrees toolbit angle. I like to keep tool overhang low and a lower angle is just fine for this. Also, the higher the angle is, the more unbalanced the flycutter will be.

Later have made the smaller one with 27.5mm diameter for 6mm toolbit. On this one the angle used was 15 degrees. As it is smaller there is less unbalanced mass, and in fact it is smaller enough to not produce excessive vibrations.

After trying both I think that if I have made the larger one with 15 degrees, I would be in trouble with vibrations. I still need, at least, a larger one. Will try other designs / angles to see if I can make it as good as these ones, without excessive unbalancing.