Hole Diameter | CNC Machining Blog

How can I mill a circle on a bridgeport milling machine?

I would like to learn how you can use a normal 3 axis milling machine to cut or mill reasonable circles in steel. machine has no cnc function although it has a digital readout on two axis. Many thanks!
The hole in a 350 mm diameter pipe and the hole diameter is about 150mm. Rotary tables are no good for this, aint got one anyway! Spoke to a guy in a pub (always a good place for reliable info) and he talked about "equation of a circle" which is pythagoras to most of us, but he was well oiled and mumbled

I know what you want to do. Its cut a nice circle in pipes without all that pattern development and grinding to shape.
OK use polar to rectangular coordinates for each of 360 degrees to get your x,y figures. you will have to remember to turn the right handle first as the order will change each quarter circle. Sketch things out on paper first and then have a trial run on some scrap.
You dont have to use 360 degrees it just depends on the finnish.
remember to get the +y -y and +x -x the right way for each quarter

Tags: axis milling machine, circle, hole, hole diameter, machine, rectangular coordinates