Fly cutter questions

[mikey]

Can fly cutters be used on a lathe as well as a mill?

What would the major working differences be?

What sort of stuff is important to understand about fly cutters to the 1st time user of one?

Thanks, very interesting thread, love learning a new method technique!!

Yes, fly cutters can conceivably be used in a lathe, although that isn't something I've seen done. You would need some way to solidly mount the work piece vertically to the cross slide so you could fly cut it.

Fly cutting is most commonly used to flatten a surface. Depending on the work and the operator, this can be done with great precision over a rather large surface area, like a cylinder head. Most commonly, fly cutting is used to prepare a work piece on a mill. Most milling projects start out as rough stock that may or may not resemble something square and you need to make it square. To do that, you fly cut it in a specific sequence so that all 6 sides are square to each other. Then you can work that piece however you need to. If the sides are not square then every single operation you do will likewise be out of square so this is an important process. You can also do the same thing with an end mill or face mill. The former is very slow and tedious, the latter is much faster but a fly cutter is usually faster still.

If you want to use a fly cutter, best get yourself a mill first.

 

[Silverbullet]

Yes, fly cutters can conceivably be used in a lathe, although that isn't something I've seen done. You would need some way to solidly mount the work piece vertically to the cross slide so you could fly cut it.

Fly cutting is most commonly used to flatten a surface. Depending on the work and the operator, this can be done with great precision over a rather large surface area, like a cylinder head. Most commonly, fly cutting is used to prepare a work piece on a mill. Most milling projects start out as rough stock that may or may not resemble something square and you need to make it square. To do that, you fly cut it in a specific sequence so that all 6 sides are square to each other. Then you can work that piece however you need to. If the sides are not square then every single operation you do will likewise be out of square so this is an important process. You can also do the same thing with an end mill or face mill. The former is very slow and tedious, the latter is much faster but a fly cutter is usually faster still.

If you want to use a fly cutter, best get yourself a mill first.

Many use the lathe like a horizontal mill. It takes a sturdy work platform with y , vertical adjustability. Ck Ables shed,,,I think,,, is his title on YouTube , he does some amazing builds with a small China lathe . Milling slotting , fly cutting and all other aspects even boring head.

 

[MarkM]

Flycutters are more for just surface finish. They can be used to bore holes accurately, use for tools, cut grooves, splines radiuses and probably more.
I made five. I don t like to stick my tool out too far so I use the next size. Here is a project I did. All the radiuses and the 1.25" hole were all done with flycutters. Those radiuses are exact. The two pcs. Put together gets you the same 1.500" and 2.500" every spot on the hole. A groove cut on some jaws I made for a small vise. These for now will be my boring head as well as regular flycutting duties.
You may want to use brazed carbide at that diameter. Much better than inserts if you can grind a tool.

 

[MarkM]

One thing that you have to be aware of grinding your tool. Be very careful adding side relief. If you take it too far you may take yourself out from having your tool on centre. Put your screws in the position with the cutting forces. Not going against them. I don t really like sticking my tool out more than an inch.

 

[WCraig]

Ck Ables shed,,,I think,,, is his title on YouTube , he does some amazing builds with a small China lathe . Milling slotting , fly cutting and all other aspects even boring head.

I searched for "Ables shed" with no luck. Can you post a link?

Craig

 

[jdedmon91]

I was thinking of using carbide insert tooling bits if that makes a difference

I made one my self that uses a tool holder that uses the unused corners of a CNMG 432 insert. Now it isn’t 4” in Dia. However you could modify the design

I’m attaching a YouTube video of the build.

Sent from my iPhone using Tapatalk

 

[Investigator]

OK, I have a plan I'm working on.......
Tell me, how important is it to have the cutting edge precisely on center? What happens if it isn't on center line?

 

[pontiac428]

To add to the question, what tool bit grinding profiles produce the best finish and performance (for surface fly cuts)? Are there any formulae for depth of cut and feeds/speeds? I am not sure that my books cover that.

 

[mikey]

OK, I have a plan I'm working on.......
Tell me, how important is it to have the cutting edge precisely on center? What happens if it isn't on center line?

Ideally, the cutting edge of the tool where it contacts the work should be on the centerline of the tool. I would try hard to make it so.

To add to the question, what tool bit grinding profiles produce the best finish and performance (for surface fly cuts)? Are there any formulae for depth of cut and feeds/speeds? I am not sure that my books cover that.

I'm assuming you're referring to a HSS tool for use in a flycutter. You are grinding a LH turning tool, the profile of which is up to you. Keep in mind what the flycutter has to do: Interrupted cuts, stock removal, fine consistent finish.

• The interrupted cut part suggests to me that M2 HSS would be the best material to use as it is the most impact resistant HSS available. Impacting cuts require greater edge strength so I would keep the relief angles to a max of about 15 degrees or so.
• Stock removal implies deep cuts. If you plan to use it to bring parts to size and rough with this tool then you are going to generate pretty healthy cutting forces. To do that, I would increase side rake to reduce cutting forces instead of increasing the relief angles, for the reason noted in bullet 1. For use in multiple materials, I should think that 12-15 degrees of side rake would work. If cutting soft stuff like aluminum, you can increase side rake and back rake a lot more.
• Fine finishes are thought to be brought about with large nose radii. You can do that but it will increase deflection. Personally, I would limit the nose radius to 1/32". I prefer to increase speed and decrease feed to improve finishes. The benefit is that increasing speed will reduce cutting forces all by itself.

I think @ttabbal made a LH Square Tool that he used in a flycutter; perhaps he can give you some input on how that worked.

I no longer use HSS because I got tired of grinding them. Inserts last much longer, work fine and give a decent finish (but not better than HSS will). Hope this helps.

 

[ThinWoodsman]

To add to the question, what tool bit grinding profiles produce the best finish and performance (for surface fly cuts)? Are there any formulae for depth of cut and feeds/speeds? I am not sure that my books cover that.

I have a couple of flycutter bits to grind, and noticed the lack of coverage in the books as well.

So far, Totally Awesome Flycutter Grind seems the best of a sparse lot. Nothing very comprehensive out there. Tom's Techniques has a Cutting Tool Geometry page with an excellent diagram for a fly cutter, though it's just the one. In the video for this he says the diagram shows a right-handed cutter and is wrong, but that seems to have been fixed.