smooth surface finish by milling?

[autobot]

Is it possile to get smooth or as close to mirrior as possible surface finish by milling or fly cutting etc? Or are there always going to be those cutting parts when you need to do more than 1 pass to clear a surface?

[txcncman]

"Smooth" is a relative term. What rA are you looking to get? Or microinch? Give us some clues. What material? What machine?

I have gotten 32 or better finishes on aluminum and steel with face mills, almost always having to run coolant.

[autobot]

Aluminum. Well I mean as close to a mirror finish and more importantly without the obvious streak marks due to the multi-pass of the end mill across the surface.

[keebler303]

Nice mold machining centers will give you a great finish.

"http://www.youtube.com/watch?v=78ANHmWyFNs"]Kitamura Mycenter-4XiF Vertical Machining Center - Pipe Mold Demo - YouTube

[Geof]

All you need is a six figure sum of money floating around in your back pocket.

The difference between machines that can produce an almost mirror finish and those that cannot is simply greater rigidity, greater alignment accuracy and better bearings both on the spindle and guideways. Although that is a big 'simply'.

On manual machines the most common cause of the streak marks is mis-alignment of the spindle centerline with the travel of the table. Then comes table wobble due to non 'perfect' guideways. If you have these optimised, which can be tedious but possible, chances are you will start to see regular imperfections that I am sure are due to bearing inaccuracies.

On lower cost CNC machines it is possible to get extremely good surfaces by moderating the feed. On these machines streaks or swirl marks are often visible at the start of a surfacing pass and they diminish along the travel. I ascribe this to the entire machine flexing which the impetus of accelerating the table up to the feed rate.

[RICHARD ZASTROW]

There are a few tools that burnish surfaces. Rollers, smooth diamond "buttons" and wiper inserts on milling cutters. Ask your tooling sales guys, they should know their products capabilities.

Dick Z

[underthetire]

We have measured a 4 right off a dura center Mori Seiki with a 6" shell mill. Looks and actual finish don't always coincide however. We do a lot of optics turning here, so what is a good finish?

[basalt]

I have had good success on aluminum by dialing in the machine head and flycutting with HSS using WD-40 as a cutting oil. The finish should be dull gray not shiny, shiny and orange peel finishes indicate that the cutter is dull and rubbing. A few strokes with scotchbrite should remove any cutter marks.
Hope this helps.
Colin