DIY micro fly cutter

       Using my micro mill, it takes a while when I resurface a material stock as I only have a 1/8 inch endmill as the biggest I can use. A fly cutter would be nice but I could not find one small enough with a 1/8 shank and is balanced enough as my mill runs at 5000rpm minimum.

       I stumbled upon a few pieces of carbide lathe bits from the scrapper and figured I just make my own. Here is the result.

I started with a brass disc and a 1/8 inch shank from a broken carbide drill.

Not having a lathe at home, I just used the mill to do the lathe work.

A bunch of the different carbide bits I got.

And it is magically completed.

Was on a roll so I forgot to take pics. The idea is there and more pics of the complete unit below.

First test cut

Size comparison with a M3 screw.

Looking good.

Testing a larger piece.

Surface looks ok.

Trying out different insert styles.


This is the best surface I got so far.

This is how my resurfacing job looks like before - going back and forth with a 1/8 bit.

Final insert arrangement that gave the best finish.

One insert would have been enough (as only one touches the part, the other was set back a little) but I still used two for balance.

The carbide bit that worked best for the use.


       This fly cutter worked well but I could only take small cuts at a time as the mill motor does not have a lot of torque. With T6 alloy aluminum at 0.37inch wide, I could go 0.4mm per pass but only 0.2mm for best finish without bogging the motor too much. It still worked wonderfully and still faster than going back and forth with the tiny end mill bits. It might be possible to offset the two inserts such that one removes bulk of the material and the other for finishing the surface, I have not tested it though but will do when I make something with this.

Page created and copyright R.Quan ©15 Oct 2017.