Tuesday , February 20 2018
Home > Lathe Projects > Free Metalworking Project Plans: A Fly Cutter

Free Metalworking Project Plans: A Fly Cutter

Material: Steel

Here’s another great weekend project from Ken, a Fly Cutter.

Here’s what Ken has to say about his Fly Cutter plans:

“No, it’s not for cutting up flies, it’s for skimming metal up to say 50mm wide.

This was also designed to screw straight onto my Unimat 3 mill spindle, so again, the rear end was drilled and tapped M14x1 to suit. Make any changes to thread size, to suit your mini mill.

Made of 30mm brt ms x 40mm long, it consists of only three parts, the body and three M6x10 grub screws – couldn’t be simpler. Just add your cutting tool, up to 8mm sq. shank.

Clamping is via two grub screws, and a jacking screw is positioned inside the slot to adjust the angle of the cutting tool.

To be honest, I have not had a lot of success with this cutter, I don’t think my mini mill is strong enough, or I have got something else wrong.

Attached are a couple of pictures, and a pdf drawing. Coming up next is a scissor action knurling tool, and there’s more after that, so stay tuned, the best is yet to come.”

– Ken

Ken originally posted these plans back in 2007 (along with 4 others) on the Metalworking section of Woodworking Australia’s Woodwork Forums. Here’s a link to Ken’s original Fly Cutter post in the Metalworking section of the forum. Check back next Thursday for Ken’s next project, a Scissor Action Knurling Tool.

Thanks for contributing Ken! If anyone has advise for Ken on why he’s not having the best of luck with his Fly Cutter, please leave a comment.

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About Tyler

Tyler is a hobby machinist and 3D printing aficionado. He teaches computer programming and web development at Highline College near Seattle. Tyler founded Projects In Metal in 2008 because he was frustrated by the lack of free plans available for hobby machinists.

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  1. Hi

    I think problems are these (most common first):

    1. Mill has not enough power (decrease cutting radius and depth of cut)
    2. Tool bit is not shaped correctly (use a regular left handed lathe tool bit with a rounded nose)
    3. Too much rpm’s (tip: 6000 / diameter_mm = RPM)
    4. Too much feed (tip: 0.1 x 1 x RPM = feedrate mm/min)
    5. Too small tool bit shank (deflects because of cutting forces)

  2. Thanks for the tips Jaakko!

  3. Oh and forgot one thing: That number 6000 is for HSS tool bits. For carbide you can multiply by 6, so the constant is 36.000.

  4. And still one, quite important detail: The fly cutters tool slot should be positioned so that when you insert a tool, the tools cutting edge is in line with the center of the fly cutter.

    Otherwise the cutting angles are changed dramatically (think of a boring bar too low or too high) and it will produce bad quality or will not cut at all.

  5. Good example of the tool slots position: http://www.aoou85.dsl.pipex.com/horizontal%20fly%20cutter1.jpg

    I think that is the authors main problem.