29 September 2016
29 September 2016,

Sure manual machinists are big on flycutters.  But conventional wisdom holds that for CNC machining you should use a face mill.  Hogwash. It doesn’t matter if you are machining by hand or CNC, physics are physics and they just don’t change.    An experienced CNC machinist knows that to get an ultrafine finish you just use a CNC flycutter.

Using a CNC Flycutter for the Finishing Pass

The first step in successful machining is to get the piece to the dimensions specified.  If you take pride in your work, you want to make sure that the final product looks good too.  That means you have one more step. The final touch is the finishing pass.  Here’s some tips.

Chip Load.  Control the chips.  If the chips are coming in contact with the work surface they can mar the finish.  Use air or coolant or a combination of both to keep chips evacuated. The important of flooding the cutting area was discussed in our blog on slitting saws.  Read more about that here.

Feeds and Speeds.  Make sure you keep the RPMs up.  The less time the material spends in contact with the tool the less possibility of edge buildup.  The less edge buildup the smoother the finish.  Whether you use the CNC Cookbook or another g-wizard calculator make sure you’ve got it set up right.


Correct Angle.  Make sure the lead angle is correct.  Higher lead angles produce better results.  A correct tool nose radius is crucial to a good finish.  When you have a large chipload in relation to the radius of the cutting edge you cleanly slice off chips.  If you have a large cutting edge radius in relation to the chipload the cutter can’t get under the chip and slice it off cleanly.  Heat will build up and that shortens the life of your tool.

Reduce Wobble and Chatter.  Make sure that the set screws are tightened properly.  If you over torque you can create the same problem as not tightening enough.

Sierra American CNC flycuttersUsing the Right CNC Flycutter

You can follow all the tips in the blog and study all the geometry in the textbooks, but if you don’t have a good CNC flycutter you aren’t going to get a good finish.

Select a flycutter by Sierra America Multi-Systems.  These flycutters out perform all others.  They are available in 3 sizes, ranging from 1 ½” to 2 ½” in diameter.  Sold individually or in a set.  Sierra American flycutters are the best because they are:

  • American made
  • Heat treated for long tool life
  • Come with large set screws for more stability
  • Balanced and ready to run at high RPMs.

small fly cuttersWhen you want the best finish use the best flycutter; use a flycutter made by Sierra American.  Demand Sierra American by name.  If your supplier doesn’t carry Sierra American ask for them to order it for you.  You can call direct (800) 576-5331 and ask for the dealer near you or just send a message.

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