Creating a Fly Cutter Bit

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ksastronomer

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Being a novice machinist I find myself searching high and low for useful information to help me get started. Information regarding how to create a fly cutter bit has been difficult to come by, so I created this guide to describe the cutting bit design I adopted. It also shares the results I got with this first attempt. While I'm sure there is much room for improvement, I hope this article is useful to other newbies fishing for similar information. I welcome your thoughts and comments.

Rick
 

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Rick,welcome to the forum. You're hitting the ground running, with a presentation like that. Since you ask, I'll try to add a few comments that may help. I have the same flycutter set.

First, there's no arguing with success. Obviously, your first bit worked for you. Good going. Since there are two ends on each tool blank, you might experiment with the other end.

You don't need to take quite so much off to get it to cut. Your drawing shows bottom clearance, looking at the end of your cutter. Just what you need. Because the bit is held at a downward angle and already has the end cut back at an angle, it gives you some back clearance. Here's the experiment: Try just rounding the tip of the bit that will contact the work with a very slight radius - say, 1/32". Then hone it sharp and flat, as you've already commented. I find a small diamond hone to be the best for this. They seem to come up on sale quite cheaply from time to time.

The amount of radius that you add to the tip depends on your use of the cutter. 1/32" radius may work well for roughing cuts, while half that may be best for finish cuts, combined with a slower feed rate.

Your pdf file is excellent. When you get it to where you want it, please submit it to the downloads or articles sections of the forum. It will indeed be useful for members.
 
I put my fly cutting tools in the bottom drawer because I couldn't get an edge on the tool to do what it was intended to do. I could not locate anything on the web that explained how to sharpen the tool for fly cutting. I think I will dig them out of the drawer and give it another try. Thanks Rick.

Patrick
 
ok guys you are talking to someone who knows nothing about this stuff but has a mill and wants to learn :)):))

so what is a fly cutter ?

thanks in advance:thumbsup:
 
With those particular fly cutters you can take a carbide soldered bit, a 1/4", 5/16" or 3/8" square and mount in one and you can get an idea of how to shape a HSS tool bit. Like Hawkeye says you don't need to take a whole bunch off like the soldered carbide but you can see what going to cut and where your relief needs to be. The radius is very important. Hope I didn't confuse the works.
dickr
 
Great comments, thanks for pitching in. Dennis, the fly cutter is a great tool for milling a large surface area on metal stock. It cleans up a surface very nicely, creating a smooth level plane. I envision using it to mill material down to a target thickness. For wide plates of material you simply mill adjacent paths along the surface until you have covered the entire plate - just like mowing, but on a smaller scale.
 
ok now i am getting it, it is used to true up a side correct. it isnt meant for large cuts correct?
 
Large areas, not heavy cuts. Several light passes are safer than trying to dig out a deep cut. And make sure the setscrews are tight enough.
 
Dennis, generally speaking, these types of cutters aren't used for large depth of cuts, but rather for their reach in width. So yes, surfacing is their strong point. I would point out however, that you must be particular about the perpendicularity of your spindle to the table. A flycutter can create a dished trough if it is run out of square. It's pretty easy to tell though. If the trailing edge of the cut still removes material, it is out of square. If it doesn't touch at all, obviously it isn't square then, and if you reverse the direction of your cut and chances are the trailing edge will cut then. If you see a moire pattern lightly in the surface, you probably have it pretty close.

ksastronomer, that is a nice writeup, and I thank you for posting it. One thing I noticed though is that you mentioned as an alternative to grinding the tool, you could have filed it. If you are using any tool steel hard enough to cut, you won't be able to file it, as it is as hard or harder than the file itself.

I noticed that it was brought up that a small radius will improve the finish of a flycut, and that is very true. And that the tool will hold up better. About the only think I don't like about them other than the dishing I mentioned is the hammering on the spindle that can happen if you run the cutter large enough to get off the sides of the material, which you really should do.
 
ksastronomer said:
Being a novice machinist I find myself searching high and low for useful information to help me get started. Information regarding how to create a fly cutter bit has been difficult to come by, so I created this guide to describe the cutting bit design I adopted. It also shares the results I got with this first attempt. While I'm sure there is much room for improvement, I hope this article is useful to other newbies fishing for similar information. I welcome your thoughts and comments.

Rick
Click to expand...



That is a very good description for newbies to learn from. A lot better than some books.

They will appreciate the time it took you to create this PDF.

My first fly cutting adventure came from watching the old timers, and OJT.


Some guys catch on to the geometry pretty quick.
 
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