11 December 2018
11 December 2018,

The fly cutter is the ultimate finishing tool. It produces a flawless finish in one pass (provided you use the right size cutter). Both manual and CNC’ers rely on fly cutters to remove small amounts of material, smooth surfaces, or even cut a gear. Take all the cutters out of a face mill but one and you’ve got a fly cutter. Here are some other interesting facts about this common shop tool

Right Hand or Left Hand?

Did you know cutters were handed just like people? Most common cutters are right handed. Most fly cutters are left handed. How can you tell the difference? It’s easy. According to Fundamental of Machine Tools, you just need to loot at the cutter straight on.

Right hand cutters rotate counterclockwise.  Left hand cutters rotate clockwise. The cutters may not know what a clock is, but they know which way to rotate. You need to know this information too.

A fly cutter has a single tooth face. That’s the forward facing surface of the tool that makes the cut.

courtesy Stuart Miles

Fly Cutting Takes Patience

If a large fly cutter can remove a large amount of material in a short amount of time, then why does fly cutting take patience? That’s because most material that is shaped with a fly cutter is a soft material. For example, if you are machining aluminum, you just can’t rush the job. Slow and steady will always win this race. Because the sharf curls when fly cutting, rotating slowly gives more time for the chips to evacuate before the cutter returns.

In addition, fly cutting any surface is a great way to tell if your bed is still flat and level. If it is not, the fly cutter will not perform evenly. For example, if the bed is slightly off, then when the cutter rotates it will either dip down or jog up as it spins.

The good news is that a fly cutter is perfect for leveling that uneven bed.

Sierra American fly cutter

Take Care of Your Fly Cutter and It Takes Care of You

No cutter lasts forever. But with proper care, your fly cutter will give you hours of excellent performance. When it is dull, just use a grinder to sharpen it and you’re ready to go again.

Prevent overheating by running at the right speed. If you aren’t sure about the feeds and speeds for the job, refer to your software. If you don’t have software, get it. The CNC Cookbook is a great place for the hobbyist to start. Overheating your fly cutter leads to a shorter life. The cutter gets dull and the mill must work harder to turn the cutter. Not good for the cutter or the mill.

Never operate the cutter backwards. Can’t believe we have to say it, but there it is. Don’t be stupid.

Do lightly oil your cutter before you store it. This prevents rust and corrosion.

Only use quality American-made fly cutters. Ask for Sierra American Multi-Systems by name where you buy your tools. A fly cutter on the fly is dangerous. Don’t get hurt by cheap foreign imports. Sierra American fly cutters are heat treated and balanced. They’ll last.

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