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Thread: Fly Cutting

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    Default Fly Cutting

    I am a home shop machinist with a Bridgeport Mill
    I have been reading about fly cutting
    using an insert in a lathe tool holder
    however I can not find any suggestions of which
    style to get. I just know it should be left handed cutting
    I would appreciate some recommendations
    Thank You

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    CCMT inserts are fairly commonly used on small boring bars for lathes. Often, there will be 2 corners of those inserts that never gets used (with the 95 ° included angle). So it might be reasonable to try to find a toolholder that will hold those inserts and make use of that corner. I know that such toolholders exist for larger shank tools, not sure how small you can get them.

    But I've used a lot of Triangular inserts for boring and facing on the mill. The relatively pointy corner of a T insert is less likely to chatter than a C insert.

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    If I understand your question correctly using the term "lathe tool holder" than that suggests carbide inserts and a single cutting edge. You can use carbide but I've never been a fan of this due to the shock of an interrupted cut which chips the brittle cutting edge. While spindle speeds are much slower I prefer using HSS for use in a fly cutter as it resists shock much better and touching up the cutting edge is much less work. Fly cutting demands you tram the mill head fairly close or you'll be cutting an angled and/or concave surface. Hot chips are thrown everywhere so guards are important or you'll catch a hot chip down your shirt or have a large area around the machine to sweep up. The other type some call a fly cutter is a multi insert tool that does use carbide inserts. This is useful for harder materials, stainless steel, or have a large plate to deck down to thickness. The multi insert type isn't as susceptible to shock like the single bit are but still have comparatively short life for the inserts, particularly in a mill like a Bridgeport. If you're new at this I suggest a "lathe tool" type of single bit using a HSS bit to get familiar for the lowest cost. Do make sure the set screws are locking the bit in for safety. Use cutting oil, set your spindle speeds per diameter and material (use guards when cutting) and find what works for you. You can always spend more money later on more expensive tooling if you need/want to. Carbide isn't always the best choice for cutting metal but it is more expensive.

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    Save yourself a lot of trouble, get something like an iscar f45st face mill 3" max diameter, square polished positive rake inserts. They also make them with integral r8 shanks, very low profile. Produces near mirror finishes with correct feeds/speeds, without beating the poor little bp spindle bearings to death. Havent rotated the inserts yet after 3 years and lots of aluminum, fair amount of steel, and a bit of cast iron (prototyping intermittent use).

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    Check out Joe Pieczynski on You Tube. He has a couple videos on fly cutting as well as many others with very useful info for both ameteur and professional machinists.

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    Quote Originally Posted by AD Design View Post
    If I understand your question correctly using the term "lathe tool holder" than that suggests carbide inserts and a single cutting edge. You can use carbide but I've never been a fan of this due to the shock of an interrupted cut which chips the brittle cutting edge. While spindle speeds are much slower I prefer using HSS for use in a fly cutter as it resists shock much better and touching up the cutting edge is much less work. Fly cutting demands you tram the mill head fairly close or you'll be cutting an angled and/or concave surface. Hot chips are thrown everywhere so guards are important or you'll catch a hot chip down your shirt or have a large area around the machine to sweep up. The other type some call a fly cutter is a multi insert tool that does use carbide inserts. This is useful for harder materials, stainless steel, or have a large plate to deck down to thickness. The multi insert type isn't as susceptible to shock like the single bit are but still have comparatively short life for the inserts, particularly in a mill like a Bridgeport. If you're new at this I suggest a "lathe tool" type of single bit using a HSS bit to get familiar for the lowest cost. Do make sure the set screws are locking the bit in for safety. Use cutting oil, set your spindle speeds per diameter and material (use guards when cutting) and find what works for you. You can always spend more money later on more expensive tooling if you need/want to. Carbide isn't always the best choice for cutting metal but it is more expensive.
    There's a lot of good advice here. My vote would be for an HSS tool also unless you're cutting a meteorite.

    Regards Tyrone.

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    Quote Originally Posted by AD Design View Post
    If I understand your question correctly using the term "lathe tool holder" than that suggests carbide inserts and a single cutting edge. You can use carbide but I've never been a fan of this due to the shock of an interrupted cut which chips the brittle cutting edge.
    Brazed carbide tools in fly cutters will cut miles of steel, they don't mind the interrupted cut. It will dull just like HSS only it will take longer.

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    With a carbide insert face mill, you can feed a lot faster due to multiple inserts, and the carbide generally allows higher cutting speeds/feeds. Another useful aspect is that although the inserts produce a 45' edge, you can sometimes employ it as a big "roughing"/surfacing cutter for non-planer features. I use lots of HSS on the BP and lathe, but the 3" facing mill (Iscar F45ST, 3" dia, 5 SEHT polished uncoated inserts) works really well and easily on the BP, no fiddling required.

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    Grinding your own tools is a machinist right of passage
    So learn that
    But carbide is so much faster
    My current small insert and a couple of tools I made two use the (other) corners

    20190201_103014.jpg

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    I 2nd the thought on going with a 2.5" to 3" face mill in the long run you will be far further ahead

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    Hi Thank You for all your suggestions
    I purchased an Iscar F45ST 3 inch diameter face mill on ebay
    I have experimented with the inserts it came with
    the inserts are unmarked
    and am pretty happy
    I purchased some Iscar SEHT-AFN IC328 inserts
    and plan to experiment more
    I also plan to learn to grind my own cutters for fly cutting
    Again thank you for all your suggestions
    practical machinist forum is an excellent resource
    Bob

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    It depends on what you are cutting, of course. We fly cut silver contacts with a HSS bit hand ground. Silver needs to have a very sharp tool. As sharp as you can get it isn't good enough and there can be no dragging or the silver will ball up. We used the radius of the grinding wheel to form a concave clearance on the end of the tool and then laid a fine stone across the radius and slid it back and forth parallel to the top of the bit. The idea of the concave surface is to hold the stone at a constant angle, eliminating rounding of the edge. The idea is to make the cut and then have the tool get away from the surface as fast as possible. We used unsulfurized gear lube instead of cutting oil to lubricate the surface and reduce scuffing. Did thousands that way with great results.

    Bill

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    One thing that hasn't been mentioned is the width of cut you can get with a flycutter. I agree with the idea that
    a 3" facemill--or in some cases, a roughing endmill--will quickly remove a lot of material but there may be situations
    on a wider workpiece where you want to finish with a single, seamless face. In this case, especially on a lighter
    machine like a Bridgeport, a flycutter can be used to cut a 6" or even wider swath in one pass...

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    Quote Originally Posted by RWasiczko View Post
    I am a home shop machinist with a Bridgeport Mill
    I have been reading about fly cutting
    using an insert in a lathe tool holder
    however I can not find any suggestions of which
    style to get. I just know it should be left handed cutting
    I would appreciate some recommendations
    Thank You
    .
    usually a series 1 bridgeport has 1 hp at spindle (after gearing) and it will vibrate and chatter a lot when you get near using 1hp plus more importantly a R8 collet has a little setscrew key that engages tool holder collet keyway.
    .
    when over loaded the set screw key gets damages and tool holder keyway is often damaged too. just saying dont plan on 0.100" depth of cuts at 4" cutting width in steel or stainless. not only will spindle easily stall or stop turning but it damages the key and keyway.
    .
    basically 1hp with average cutter you can remove about 0.8 cubic inches per minute milling 1018 steel. but your machine doesnt have the hp or rigidity or a heavy duty enough tool holder system to do it very good for long periods of time. plan on limited cuts or plan on doing repairs
    .
    usually even a 1"dia end mill needs more hp that a bridgeport has and it will vibrate too much from heavy cuts. my experience is go easy on the flycutting

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    Quote Originally Posted by DMF_TomB View Post
    .
    usually a series 1 bridgeport has 1 hp at spindle (after gearing) and it will vibrate and chatter a lot when you get near using 1hp plus more importantly a R8 collet has a little setscrew key that engages tool holder collet keyway.
    .
    when over loaded the set screw key gets damages and tool holder keyway is often damaged too. just saying dont plan on 0.100" depth of cuts at 4" cutting width in steel or stainless. not only will spindle easily stall or stop turning but it damages the key and keyway.
    .
    basically 1hp with average cutter you can remove about 0.8 cubic inches per minute milling 1018 steel. but your machine doesnt have the hp or rigidity or a heavy duty enough tool holder system to do it very good for long periods of time. plan on limited cuts or plan on doing repairs
    .
    usually even a 1"dia end mill needs more hp that a bridgeport has and it will vibrate too much from heavy cuts. my experience is go easy on the flycutting
    WTF Tom?!

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    i have damaged key and key way on bridgeports before flycutting up to stall point. its easy to do manually milling. boss gives you a job and wants it done as fast as possible. when on low gear you have a relatively large amount of cutting forces but the wack wack wack is hard on the mill
    .
    set screw key replacement usually you need the maintenance manual as repairing the head often requires certain steps to do repairs successfully. set screw replacement is a relatively annoying thing to have to do. when damaged none of collets want to go in quite right cause set screw key squashed bent a bit
    .
    obviously if i knew it would get damaged so easily i wouldnt have pushed the mill so hard
    .
    this is very similar to using a big tap on a small lathe with the headstock lock pin engaged to hold chuck from turning. obviously if using a 1.5" dia tap and using a 18" wrench to turn tap the little lock pin maybe 0.2" in dia engaged in a soft aluminum or zinc alloy gear aint going to hold the back against the tapping force. once damaged repairs are not so easy without major disassembly. just saying you got any machine especially low hp machines got to think what damage will occur if you overdue it. sometimes things break immediately. other times things get bent or deformed. you can say those parts acts as a fuse but the fuse is not so easy to replace if damaged

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    Good morning all.


    As Huflungdung says, triangular inserts will work on a fly cutter. Just for fun I made a rather large fly cutter for my mill using an 18mm left handed boring bar that takes TPUN16 triangular inserts, & it works very well on everything from alloy to high carbon steel. It's much slower than my face mills, but for a finish pass on wider items it's the Dog's wotsits.


    Cheers.

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    Quote Originally Posted by DMF_TomB View Post
    i have damaged key and key way on bridgeports before flycutting up to stall point. its easy to do manually milling. boss gives you a job and wants it done as fast as possible. when on low gear you have a relatively large amount of cutting forces but the wack wack wack is hard on the mill
    .
    set screw key replacement usually you need the maintenance manual as repairing the head often requires certain steps to do repairs successfully. set screw replacement is a relatively annoying thing to have to do. when damaged none of collets want to go in quite right cause set screw key squashed bent a bit
    .
    obviously if i knew it would get damaged so easily i wouldnt have pushed the mill so hard
    .
    this is very similar to using a big tap on a small lathe with the headstock lock pin engaged to hold chuck from turning. obviously if using a 1.5" dia tap and using a 18" wrench to turn tap the little lock pin maybe 0.2" in dia engaged in a soft aluminum or zinc alloy gear aint going to hold the back against the tapping force. once damaged repairs are not so easy without major disassembly. just saying you got any machine especially low hp machines got to think what damage will occur if you overdue it. sometimes things break immediately. other times things get bent or deformed. you can say those parts acts as a fuse but the fuse is not so easy to replace if damaged
    WTF are you talking about? If the pin in an R8 taper you should thrown that POS out years ago.
    W

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    the set screw key for R8 collet keeps it from spinning and damaging taper. so its a choice stall motor if cutting too much or have collet spin damaging taper on overload.
    .
    my point is a series 1 bridgeport like all machines has its limits and its usually roughly 1hp and even using 3/4hp at the tool you can get serve vibration chatter tool damage and possible machine damage at collet set screw key especially at low rpm. when cutting the same cubic inches per minute the slower the rpm the higher the cutting forces
    .
    thus a 1" end mill cutting 1.0 cubic inches per minute uses less torque than a 4" dia cutter going 1/4 the rpm it is using 4x the torque cutting the same 1.0 cubic inches per minute. the slow rpm wack wack wack is actually harder on the machine.
    .
    when manually milling or using feed its easy to go from 0.5 inches per minute to 1.0 inches per minute and over load machine especially if taking 0.1" or more depth of cut with a 4"dia flycutter milling steel and especially harder metals like 304 SS
    .
    4" dia flycutter on a series 1 bridgeport just saying you have to be careful to not overload it and damage the machine. the slow rpm of a flycutter can actually be wacking it at over 500lbs of force. also easy for part to move in a vise obviously.

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    An old timer called fly cutters "Spline wreckers".

    Bill

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