# Safe alternative to fly cutter?



## compressor man (May 23, 2010)

I have not long had my mill (X2) and am beginning to amass tooling for it. I feel that I need a fly cutter to surface large swathes of metal but have heard negative comments on this tool. The fact that it is not constantly in contact with the workpiece is hard on the mill (so I have read here). Looking for alternatives, I have found on ebay a 3" 5 FLUTE R8 INDEXABLE CARBIDE END MILL . Would this be a better (safer for the mill) alternative than a fly cutter? Could an X2 handle something like this or are my fears unfounded?


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## Kermit (May 23, 2010)

3 inch could be just a little to much 'tool' for the little X2

I've got a 1 inch, 2 insert carbide endmill. Taking a large bite without stalling is not the problem. The motor and spindle bearings overheat something terrible when I use the endmill too agressively. Too much for the machine to do as a steady feed. I have to take smaller bites or give the motor and bearings lots of cooling off time.

Kermit


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## Tin Falcon (May 23, 2010)

I have had my x-2 since October of 2001. And I have used fly cutters on it with no apparent detriment. I think one of he concerns is the gear train taking a beating. My gears held up fine. But if you change to a pulley system the gears are removed. The pulleys are a popular and recommended upgrade. The pulleys reduce noise and vibration. 
I was taught to use fly cutters in USAF tech school. They are versatile and easily made in the shop. With a bit of creativity, and a bit of tool grinding skill you can do a lot with them.Uses include: surfacing , boring ,counter boring, slotting on the top or side of part, you can round corners, or do decorative edges and even cut gears. 
You can usually find a set of three fly cutter for under $20. 
While there are certainly advantages of getting a indexable surfacing cutter I do not think you can beat the price simplicity and versatility of the humble fly cutter for a small mill in the home shop. 
Tin


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## kvom (May 23, 2010)

Flycutters are adjustable in width of cut, so that is is usually possible to set it to just over the width of the work. Then with the spindle centered the tip of the tool will contact the edge of the work at a nearly tangent angle.


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## cidrontmg (May 23, 2010)

I´ve used flycutters first with my lathe+vert. slide, and now on a small Quantum mill,
and I find them just wonderful things. Cheap, easy to make, easy to sharpen, easy to adjust for many types of jobs, and they sure make a nice finish. I´ve never had a thing like the "3" 5 FLUTE R8 INDEXABLE CARBIDE END MILL ", and I certainly wouldn´t want something like that spinning in my mill. That´s >70 mm in diam! The biggest endmill I have is 12 mm, and I don´t use that very often, if at all, it´s just too big. Maybe if I had a Bridgeport or a Deckel, but not on a Quantum BF16 Vario... But a flycutter set to sweep 50 mm (2") is just fine with me. 
Flycutters should not be pushed, they don´t like deep cuts. Light cuts, many passes is the ticket.


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## IanN (May 24, 2010)

Hi,



			
				aermotor8  said:
			
		

> i was always told that fly cutters were for light finish cuts.
> if you have allot of metal to remove you should use a roughing end mill.



If you do the arithmatic, for a given surface speed a single edged fly cutter will remove less material than a multitoothed end mill in a given time. Also, the end mill can take a deeper cut. This means that the end mill will get the job done quicker, but (as others have pointed out) the surface finish produced by the fly cutter is visually more attractive - it does not have the "stripes" that you get with multiple parallel passes of the end mill.

On the other hand, the wide sweep of the flycutter will amplify the effects of "tramming" errors.

Ian.


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## Troutsqueezer (May 24, 2010)

I'm with Tin. Installing the belt and pulley system was the best improvement I've made to my X2. I haven't had any probs with flycutting. 

-T


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## compressor man (May 24, 2010)

If I would have thought this thing through I would not even have asked this. I wonder what I was thinking? *club*
Especially after hearing that a "mere" 1" would put this little mill to the test. I think that a flycutter may not be such a poor alternative after all. Surely the potential/possible abuse from this tool is certainly less difficult on it than an overheated motor and speedcontroller that would result from a too-big endmill!! 

Feeling dumb now...


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## Tin Falcon (May 24, 2010)

do not feel dumb. No dumb questions here . we all learn as we go. machining is not something you lean over night. entire books have been written about such subjects as : Cutting tool selection , cutting fluids, machining plastics, selection of metals, Lathe operations , milling machines ..... The machinist handbook, the MSC and McMaster-Carr catalogs are 4" thick for a reason There is lots to learn.
Tin


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## firebird (May 25, 2010)

Hi Chris

There's another post on fly cutting further down but if you haven't seen it here's my first attempt.





Here I'm using a left hand turning tool to clean up the face of some 3 1/2 x 3 1/2 angle iron. I have just finished making a fly cutting tool that uses TCT and that works just fine.

Cheers

Rich


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## cidrontmg (May 25, 2010)

Here´s some of my recent efforts at fly cutting. Done with the Quantum mill, cutter sweep +/- 60 mm dia, and the blocks are brass. They started as 40x40 mm, but I needed them at 37.5x37.5mm, and the excess 2.5 mm was shaved off with the fly cutter (half that from all faces). It´s not the best of pictures, but it shows what the surface (should) look like with a reasonably well trammed mill (and with a not too sharp a cutter edge ;D). The cutter should cut coming and going, so there are two sets of arcs, "concave and convex". The surface is really silky smooth, I had to fumble some with the lighting to get the effect most visible.
It won´t much matter, though, I´m going to turn (= I already have) the blocks circular, leaving just a 6mm wide square part in them.


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