Welcome to the Mirage Machines Portable Performance Blog

How to machine an ASME B16.5 flange finish


Finding information on the correct ASME specifications for flange surface finishes is easy enough, but how do you actually machine the correct flange surface finish you need?

The principle of surface finishes for flanges facing is easy enough to understand and is simply determined by the depth of cut, the feed rate and the nose profile of the cutting tool.

Let’s assume you want to create a stock finish on a raised face flange that’s positioned in a vertical orientation.

To do this you will need a flange facing machine, which are available as internal and external mount versions and in a number of different sizes. In most situations a pneumatically powered machine will be the most appropriate option, but hydraulically powered versions are available too.

Example: How to re-face a 21” diameter flange

Machining an ASME stock finish onto a flange face of this size can be carried out using a Mirage MM610i internally mounted flange facing machine.

Machine Setup

The set up process of an ID mounted type of flange facer begins with the installation of the base unit into the flange bore. The base is lowered into the bore and locked in place by tightening the 4 jacking bolts. This also has setting straps attached for initial alignment with the top of the machine which are removed prior to machining.

Next, the machine is bolted onto the base unit and the whole assembly is levelled more accurately using the 4 adjustable jacking bolts. Checking the machine is perfectly level carried out using a clock dial indicator.


Above: A Clock Dial Indicator


If the flange facer is to be mounted in the vertical orientation it will need to be balanced by adding and adjusting the supplied counterweight assembly. Balancing the machine ensures the facing arm rotates at an even speed, helping to produce an even finish around the flange surface.



Next, a suitable round nose cutting tool with the correct end radius is inserted into the tool post. To achieve a ‘stock finish’ ASME states that the tool nose should have a radius of 0.063” (1.6mm).

The clock dial indicator is now set to zero and then a depth of cut is added by turning the feed knob located on the top of the toolpost. The depth of cut for a stock finish should be 0.006” (0.15mm).

The toolpost should then be moved to the edge of the flange ready for the correct gear to be selected.

Gear selection

On the standard Mirage MM610i flange facer there are 2 gears providing finishes of Coarse (32 grooves per inch) and Fine (128 grooves per inch).

In addition, by using a different pitch ball screw provided with the machine, surface finishes with 45 and 179 grooves per inch can be achieved.  An optional ball screw makes it possible to machine 56 and 224 grooves per inch.

To create a stock finish using the Mirage MM610i flange facing machine, simply choose facing ‘In’ using the lever ‘A’.


Now turn on the pneumatic supply and the machine will start to rotate and begin facing the flange surface. The machine is stopped by switching of the air supply.


Summary: How to create an ASME B16.5 stock finish

  • Select the correct flange facer based upon flange and mounting diameters
  • Install base and remove setting straps
  • Attach machine and carry out fine levelling adjustment
  • Insert 1.6mm diameter round nose tool into toolpost
  • Set clock dial to zero and apply 0.15mm depth of cut
  • Move toolpost to position cutting tool at thedge of the flange
  • Select correct gear to produce a 32 grooves per inch
  • Switch on the power supply

You can learn more about the full range of Mirage flange facing machines by downloading our buyers guide. If you are ready to discuss your requirements you can get in touch with your regional contact Mirage contact here.

 Download the Flange Facing Machine Buyers Guide

Recent Posts