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  • #31
    Originally posted by plunger View Post

    I was trying to wrap my head around that. But if you make the longer cutter inboard of the outer cutter would it not then make a difference.
    Yes it would ! Your fly cutter has just become smaller !
    Best Regards:
    Baron J

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    • #32
      Originally posted by plunger View Post
      If you have a fairly substantial milling machine and wanted a decent homemade flycutter does inertia or mass of the flycutter go anywhere into making a better flycutter. Would a bigger chunk of steel give a smoother cut by absorbing the interupted cut. In other words using lets say a chunk of steel of 250mm by 20 mm thick give a better finish than what bented showed on those t bar type black flycutters. ?
      Also if one staggered three hss cutters at different height would it help in taking deeper cuts?. In other words would you get a first cut, second cut and then final cut so there is less work done onr the final or longest protuding hss cutter?
      Laws of physics always apply. A body in motion tends to stay in motion. The larger fly(wheel) cutter's inertia will help smooth out the interrupted cut, but this benefit will be felt more in the reduced shock from an interrupted cut on the machines drive line than on the finished part. The larger and heavier the machine, the less it's influenced by the cutter, but the workpiece still sees that interrupted cut.

      Staggered cutters are an excellent way of reducing chip load per tooth. How much benefit do you wish to gain? If the chip load is heavy enough, and the cut deep enough, then a fly cutter might not be the weapon of choice. This is where the heavy face mills with indexable inserts start to pay off. They have tremendous metal removal rates, and have tool geometry designed to require the least amount of power to attain those removal rates.

      Often times the flycutter size is selected to match the workpiece size so that a step-over cut is avoided. This is especially important if the machine head is not, or can not be in the best of alignment with the table travel.

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      • #33
        i have been trying to understand the obsession wih flycutters for a few decades. still dont. why dont you get a facemill for $40?

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        • #34
          Originally posted by dian View Post
          i have been trying to understand the obsession wih flycutters for a few decades. still dont. why dont you get a facemill for $40?
          I think tom_d answered that above: "Often times the flycutter size is selected to match the workpiece size so that a step-over cut is avoided. This is especially important if the machine head is not, or can not be in the best of alignment with the table travel."

          BTW does that $40 include the inserts and cover a 8" (200mm) width in a single pass?
          The flycutter is a popular shop project because it can easily be made to do that, for a lot less money -- and gain some valuable machining experience. The commercial shops that I have been in, all have face mills -- that cost more than my entire lathe. A home shop person usually won't spend that kind of money.
          25 miles north of Buffalo NY, USA

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          • #35
            Originally posted by nickel-city-fab View Post

            I think tom_d answered that above: "Often times the flycutter size is selected to match the workpiece size so that a step-over cut is avoided. This is especially important if the machine head is not, or can not be in the best of alignment with the table travel."

            BTW does that $40 include the inserts and cover a 8" (200mm) width in a single pass?
            The flycutter is a popular shop project because it can easily be made to do that, for a lot less money -- and gain some valuable machining experience. The commercial shops that I have been in, all have face mills -- that cost more than my entire lathe. A home shop person usually won't spend that kind of money.
            For cylinder head skimming of an ali block a flycutter works real well I would think for a penny in costs for a homeshop environment. And here in Darkest Africa you are not going to buy a facemill for 40 dollars.

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            • #36
              Originally posted by plunger View Post

              For cylinder head skimming of an ali block a flycutter works real well I would think for a penny in costs for a homeshop environment. And here in Darkest Africa you are not going to buy a facemill for 40 dollars.
              It's hard to find them here in the US at that price too. The usual Chinese importers want well over $100 not including inserts. And none of them have an MT3 shank that I could use, I would have to get a straight shank and use it in a chuck. So the flycutter with some HSS is indeed the way to go.
              25 miles north of Buffalo NY, USA

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              • #37
                Originally posted by BaronJ View Post

                That is a little bit on the expensive side for a hobbyist tool !
                He’s saying “like that one” as in designed like that. That particular one is pretty big but the concept is simple and can be done in expensively. It looks like a cheap boring bar welded to a shank.

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                • #38
                  if the tram is out a fly cutter is a really bad idea for a cylinder head. dou get a dish. the picture in post #1 looks like 4". they come with inserts, replacements are $1.50 and the arbor is another $15 or so. id chose stepover anytime over having to mess with sharpening cutters and getting bored to death. if you dont have $50-100 for a facemill you shouldnt be machining.

                  but yes, a good way to gain machining experience, as you usually wind up doing such "projects" at least twice, before they work. come on, folks, you only live once.

                  edit: somehow its often assumed material is free. usually its not the case. if i order steel it ends up around $10/lbs and even ebay-drops are not much cheaper. besides bob said he would use a lathe tool, must cost something too. and if you are in the out back without access to commerce, take a disc and attach 6 inserts to it. wait, you dont have inserts either, right?

                  imho flycutters are mental dynosaurs from the period where indeed only professional facemills were available, still spooking around in "bedside-readers".
                  Last edited by dian; 04-18-2021, 10:18 AM.

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                  • #39
                    Originally posted by dian View Post
                    i have been trying to understand the obsession wih flycutters for a few decades. still dont. why dont you get a facemill for $40?
                    And, just WHAT do you suppose the difference is between a "flycutter" and a "facemill"?

                    Not a great deal, actually. And, your $40 purchased facemill is a wild dream....... Maybe YOU once got one from your brother-in-law for $40, but it just "don't happen" in general. More like $90 to $140, maybe, for smaller, low quality versions.

                    Options include:

                    1) Use a shaper (so who has one big enough?)

                    2) Use a large shell end mill (I have one 4 or 5" diameter, but most do not)

                    3) buy a flycutter or make a flycutter than uses the cutters YOU ALREADY HAVE for lathe work, and using metal YOU ALREADY HAVE.

                    4) Buy a commercial facemill for well over $100, and then spend another $40 outfitting it with inserts designed for the purpose.

                    Many prefer to use a single point cutter, such as the traditional flycutter. That avoids "grooving" because there is only one cutter. A flycutter of that type is a facemill with one edge. Above in this thread has been shown one with two cutters, which is now even more obviously a variety of facemill.
                    CNC machines only go through the motions

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                    • #40
                      Originally posted by dian View Post
                      if the tram is out a fly cutter is a really bad idea for a cylinder head. dou get a dish. the picture in post #1 looks like 4". they come with inserts, replacements are $1.50 and the arbor is another $15 or so. id chose stepover anytime over having to mess with sharpening cutters and getting bored to death. if you dont have $50-100 for a facemill you shouldnt be machining.

                      but yes, a good way to gain machining experience, as you usually wind up doing such "projects" at least twice, before they work. come on, folks, you only live once.

                      edit: somehow its often assumed material is free. usually its not the case. if i order steel it ends up around $10/lbs and even ebay-drops are not much cheaper. besides bob said he would use a lathe tool, must cost something too. and if you are in the out back without access to commerce, take a disc and attach 6 inserts to it. wait, you dont have inserts either, right?

                      imho flycutters are mental dynosaurs from the period where indeed only professional facemills were available, still spooking around in "bedside-readers".
                      I don't have $50 or $100 for a face mill --- oh but I still machine, and as far as tram being out you just simply make sure it's not,,, tram is of the utmost importance at all times so get it freaking right... Note the proof of a good tram with the nice crosshatch pattern, and this was not a simple clean up it was upping the ante on my comprendo ratio of my Del-Sol. fact is - is my flycutter not only makes a facemill look like it's standing still - it keeps me from wearing out the leadscrew on the X axis...


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                      Below is a pic of a properly engineered flycutter, It was built from total SCRAP material so did not cost me a penny - the black lower lathe turning tool with insert I already had, the longer one mounted in the cutter I built again from scrap, the set screws are in the correct positioning so they do not get loaded by the tooling during the cut as they press the tool against the stout wall of the flycutter,

                      there is no 30 or 45 degree angle - that's when machinists were "frightened" to have the cutter base so close to the work piece as they thought it bad practice due to gremlins and such, the insert hangs down .018" further than another other rotational pieces - this is ample room for clearance even for chips but if you get frightened keep an air hose by and blow them off once in awhile,

                      All my swath adjustment goes to increasing the radius - why would you want to toss half of that away with a 45 degree cutter that also gets further away from the quill at the same time making your work more unstable? the Cutter always remains in good balance by your decision of what size swath you need and selecting the proper length cutting tool... Yeah - it's a beautiful thing.



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                      • #41
                        Originally posted by dian View Post
                        i have been trying to understand the obsession wih flycutters for a few decades. still dont. why dont you get a facemill for $40?
                        Because face mills in days gone past needed careful sharpening and at one point the ones with inserts cost the world. And until the last 10 to 15 years were costly things. So a historically made and used single point fhy cutter made, and still makes, more practical and financial sense to a hobbyist with shallow hobby money pockets.

                        But these days with far less expensive options out there using a face mill does make a lot more sense as an option. Still..... this is a hobby. And so flycutters are still common and are far easier to make than something that needs to be trued carefully to get matching or correctly aligned step cuts.

                        And there's still the issue of minimum depth of cut needed for some inserts in order to get a nice finish. And the power needed to drive a multi tooth cutter if a minimum depth of cut to get a good finish off the inserts is something a lot more generous than what can be done with fly cutter.
                        Chilliwack BC, Canada

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                        • #42
                          Originally posted by J Tiers View Post

                          And, just WHAT do you suppose the difference is between a "flycutter" and a "facemill"?

                          Not a great deal, actually. And, your $40 purchased facemill is a wild dream....... Maybe YOU once got one from your brother-in-law for $40, but it just "don't happen" in general. More like $90 to $140, maybe, for smaller, low quality versions.

                          Options include:

                          1) Use a shaper (so who has one big enough?)

                          2) Use a large shell end mill (I have one 4 or 5" diameter, but most do not)

                          3) buy a flycutter or make a flycutter than uses the cutters YOU ALREADY HAVE for lathe work, and using metal YOU ALREADY HAVE.

                          4) Buy a commercial facemill for well over $100, and then spend another $40 outfitting it with inserts designed for the purpose.

                          Many prefer to use a single point cutter, such as the traditional flycutter. That avoids "grooving" because there is only one cutter. A flycutter of that type is a facemill with one edge. Above in this thread has been shown one with two cutters, which is now even more obviously a variety of facemill.
                          please check my "wild dream" online. what i quoted are curent prices. and as to low quality, a home made flycutter will cut better, yes?

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                          • #43
                            Originally posted by dian View Post
                            and as to low quality, a home made flycutter will cut better, yes?
                            Why wouldn't it?

                            You are making "home made stuff" with it...... Are you saying that your technique is so bad that the flycutter you make would wobble around, cutting unstable surfaces?

                            I suspect not. What does it have to do?

                            ALL it has to do is to hold the cutter solidly in position. Then you need to tram the mill

                            If you cannot make a flycutter that is solid, then perhaps knitting, or Mah-Jong are better pastimes for you.

                            Is that a bit cold? Well, YES. But a flycutter is a single piece of metal, which is turned, milled, drilled, and tapped in extremely basic ways. A project which is often suggested for beginners.

                            That wild dream....... In the US I have not seen those low prices for a face mill tool that I would consider having spinning near me..... Call me crazy, but I do not think buying such a thing from "some guy in china" is a good plan.

                            "Shars" is a low cost source here that has some potentially "sketchy" stuff, although mostly it is decent. All import of some type. No $40 prices there.
                            Last edited by J Tiers; 04-18-2021, 01:02 PM.
                            CNC machines only go through the motions

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                            • #44
                              I think the whole point of a flycutter is that you can cut something wider than 50mm. You can find chinese-made tooling at banggood around $40, but I've onlly wasted my money there once... lesson learned. Like i said, a decent face mill that is larger than 50mm will be well over $100, I've looked.
                              25 miles north of Buffalo NY, USA

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                              • #45
                                Hi Guys,

                                A lot of interesting posts in this thread ! I wonder how many have cut dovetails using a fly cutter ?

                                Up to the beginning of WW2 fly cutters were a common lathe tool. Its only really the advent of vertical mills that things like face cutters came into use. I note that "tramming" has been mentioned, few realise that the tram on a mill becomes much more important as the width of the cut gets bigger, however this isn't an issue on fixed head mills. Once you start talking "Side & Face" mills you also need the horsepower to drive them, most hobby mills struggle with a 20 mm drill !
                                Best Regards:
                                Baron J

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