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  • #16
    Originally posted by darryl View Post
    Ok, you say arbor size .75- why not turn a matching taper on the square stock so it can be inserted directly into your spindle instead. Maybe I'm missing something-

    [snip]
    What you missed is what I didn't say 😁 My spindle takes a type Y double angle collet. They're small - the largest is 1/2" & the closing nut only has 0.580+- opening. So making the fly cutter arbor to fit the collet socket would gain very little.

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    • #17
      Originally posted by BCRider View Post

      ...
      And the smaller swept diameter you are indicating with that point on the tool means that it'll be more in tune with the required 1/2" arbor. I'm seeing it end up at around a 2" swept diameter. So relatively small by most standards but in keeping with your limit on the shank diameter.
      yeah, it's in tune with the mill size itself: it's a Rusnok head, 1/4(!)hp.

      It does mean that you'll be rotating in the reverse direction. Not a big deal other than remembering to push the right button or flick the switch the right way.
      It does run both directions. But I'm thinking that I should do the mirror image, so that I can use a left-hand turning tool, as it's rarely used on the lathe.

      [snip]
      One other thing you might consider since you're limiting the diameter and shank size and thus working within the rigidity limits. If you swap your 1/2" square cutter for a 3/8sq that would also give you a beefier thin side due to the smaller cutter. And for the size of the sweep a 3/8, or even 1/4 square tool bit would be just fine.
      The tool that I am planning on using is an index holder, so I'm stuck with 1/2". (I've gotten to like not sharpening bits.)

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      • #18
        Originally posted by BaronJ View Post
        Hi Guys,

        I posted my fly cutter design on here a little while ago !

        Click image for larger version

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        [snip]
        I was going to make a cutter whose cutting radius was adjustable. I just assumed that would be desirable. But is it?

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        • #19
          Originally posted by Bob Engelhardt View Post

          I was going to make a cutter whose cutting radius was adjustable. I just assumed that would be desirable. But is it?
          The opposite of adjustable is rigid. In machining rigid is a desirable quality. Making a fly cutter is a basic, do it yourself home shop project. Even store bought ones can be had fairly inexpensively. I would prefer to have multiple rigid fly cutters in an assortment of sizes rather than one less rigid adjustable one.

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          • #20
            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?
            Last edited by plunger; 04-17-2021, 04:58 AM.

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            • #21
              Originally posted by Bented View Post
              The fly cutters that utilize cheap triangular positive rake inserts work a charm on light milling machines, either make one or buy one and you will not be disappointed.
              Similar to this
              http://www.kristitool.com/shop/b-52-fly-cutter/
              That is a little bit on the expensive side for a hobbyist tool !
              Best Regards:
              Baron J

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              • #22
                Originally posted by Bob Engelhardt View Post

                What you missed is what I didn't say 😁 My spindle takes a type Y double angle collet. They're small - the largest is 1/2" & the closing nut only has 0.580+- opening. So making the fly cutter arbor to fit the collet socket would gain very little.
                Hi Bob, Using a 12 mm (1/2" inch") spindle won't make too much difference, I've seen and used much bigger fly cutters on 12 mm shafts. Thinking about it how many hole cutters only use 6 mm (1/4" inch) shafts. I've got a four inch one that is on a 1/4" inch shaft, mind you it is much less likely to bend with a symmetrical load on it.
                Best Regards:
                Baron J

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                • #23
                  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?
                  Hi Plunger, If you think about it the cutter that sticks out the most is going to do all the work ! Yes the mass of the disc does make a difference ! However I wouldn’t be using a 10" inch fly cutter !!!
                  Best Regards:
                  Baron J

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                  • #24
                    Originally posted by BaronJ View Post

                    Hi Plunger, If you think about it the cutter that sticks out the most is going to do all the work ! Yes the mass of the disc does make a difference ! However I wouldn’t be using a 10" inch fly cutter !!!
                    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.

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                    • #25
                      Originally posted by Bob Engelhardt View Post

                      I was going to make a cutter whose cutting radius was adjustable. I just assumed that would be desirable. But is it?
                      Yes it is, very...

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                      • #26
                        Plunger you are correct.
                        John b. SW Chicago burbs.

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                        • #27
                          Originally posted by BaronJ View Post
                          Hi Guys,

                          I posted my fly cutter design on here a little while ago !
                          I also posted a drawing, but don't seem to be able to locate it at the moment.

                          The shaft on this one is 20 mm and the disc is 20 mm thick. I'm using 1/4" square hss tool bits.
                          I Like that design, it looks like it cuts smoothly, and its easy to make.
                          25 miles north of Buffalo NY, USA

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                          • #28
                            Originally posted by Bob Engelhardt View Post

                            I was going to make a cutter whose cutting radius was adjustable. I just assumed that would be desirable. But is it?
                            How about a flycutter whose radius is 12/pi ? That way the SFM equals the RPM. I think that's what Paul Alciatore did on his.
                            25 miles north of Buffalo NY, USA

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                            • #29
                              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.
                              I don’t think you need radial stagger. As table feeds each tip will “see” something to cut as it takes its turn in the cut.

                              Some insert face mills have a wiper insert that puts the finishing touch on the cut.

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                              • #30
                                Originally posted by Bob Engelhardt View Post

                                I was going to make a cutter whose cutting radius was adjustable. I just assumed that would be desirable. But is it?
                                It depends upon what you are prepared to trade off ! Rigidity or swept area. Don't forget that you can always move the "Y" slide to get a wider cut.
                                Best Regards:
                                Baron J

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