Carbide tangentials for small lathes

Discussion in 'Tools' started by Niels Abildgaard, Aug 19, 2016.

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  1. Aug 19, 2016 #1

    Niels Abildgaard

    Niels Abildgaard

    Niels Abildgaard

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    A friend of mine still feel happy with a Myford Super Seven we bougth together
    in 1964.The belt has been changed to Powertwist and motor is 3phase VFD.
    I made him a 3 mm round carbide tangential tool some times ago.

    [ame]https://www.youtube.com/watch?v=VZvs_4cADZ8[/ame]

    He uses it for most turning to day but I was never really happy with the Carbide fixing screw.It was a modified UNF 3/8 24 TPI.
    Metric fine thread screws are not easy to find and I want to try a differential screw that is made from a M8 countersunk with a UNF 3/8 head thread.
    This gives a resulting movement of 0.2 mm per turn.
    I have also invested in a swing grinder with a diamond disc and can modify 2 times 2 mm square carbide to very precise limits.
    A start has been made on a pair of Myford specific holders for 3 mm round and 2 times 2 almost square carbide.
    It is my hope that the Myford Church will test the holders compared to the most expensive QCTP systems,but in the meantime I will post pictures as I go along.First picture shows about 2 hours work.
    Material is 20 times 30 mm hot rolled steel.

    WP_20160819_004[1].jpg

    svingsliber[1].jpg
     
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  2. Aug 20, 2016 #2

    Niels Abildgaard

    Niels Abildgaard

    Niels Abildgaard

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    Have 2 hours more work and the round tool one can be ready in short time but the almost square need a press operation before being threaded and made beatifull.

    WP_20160820_002.jpg

    WP_20160820_007.jpg
     
  3. Aug 20, 2016 #3

    Niels Abildgaard

    Niels Abildgaard

    Niels Abildgaard

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    Pressforming complete

    WP_20160820_026.jpg

    WP_20160820_034.jpg
     
  4. Aug 20, 2016 #4

    Nick Hulme

    Nick Hulme

    Nick Hulme

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    Niels,
    Do you really mean QCTP or are you thinking of Inserted Tooling? If it's the latter then you have a point, up to a point, but still need to address many issues if you want to "Replace" them.

    Turning to LH & RH shoulders is one job where I reach for;
    an inserted parting tool (what I'd normally use on Brass);
    a pair of inserted tools in quick change tool holders (shown on Brass in the first photo but usually for Stainless/Titanium);
    an inserted profile cutter (big jobs where huge, fast material removal is required).

    If it's really the QCTP you aim to replace then you have a very steep slope to climb (the second photo shows some of the more common tooling I regularly use), most users of quick change tool posts have them to allow a wide range of tooling to be repeatably mounted, for many this includes not just turning tools but clamp and cut knurling tools, roller boxes, die heads, radius turning tools, boring bars, internal and external threading tools, grinding and milling spindles and more.

    I do some reasonably sized work on my long bed Super7, the QCTP with inserted tooling will give me 8mm reductions on stainless bar with showers of hot chips but no flex issues, the third photo shows a length of 30mm stainless in a chuck (although I'd more often mount round work up to 30mm in the ER40 nose of the spindle).

    If I use tangential cutting tools they will be a great addition to my arsenal, a quickly sharpened general purpose material removal tool, they won't be a replacement for something else though, and they'll have to be in quick change tool holders! ;-)

    - Nick

    Turning to LH & RH shoulders.jpg

    QCTHolders.jpg

    30mm Stainless.jpg
     
  5. Aug 21, 2016 #5

    Niels Abildgaard

    Niels Abildgaard

    Niels Abildgaard

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    I remember Myfords as wildly overprized amateur machines in dire need of more rigidity.
    Last nigth was the first try of my differential screw theme.The closing action is very nice and swiss.
    It is nessecary to think of a scheme for hindering rotation of the M8 nut.
    The screw head has been mahined to UNF 3/8 and runs direct in holder.
    Hacksawing is good for health but i have to think of a better way of positioning the almost square tingh during first pressing.

    WP_20160821_001[1].jpg

    WP_20160821_005[1].jpg

    WP_20160821_006[1].jpg

    WP_20160821_008[1].jpg
     
  6. Aug 21, 2016 #6

    Nick Hulme

    Nick Hulme

    Nick Hulme

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    They still are in some quarters, I bought mine as an ex-production machine before model engineering demand via the internet pushed the prices up beyond actual worth

    Yours must have been worn out, poorly utilised or badly adjusted, or perhaps mine being the long-bed with 31" between centres and having the heavier bed casting doesn't suffer from the rigidity problems yours did.

    Amateur is not a slight in English, it simply means that one doesn't do it for a living.
    On the other hand professional means one does it for a living and not necessarily that one is any good at it ;-)

    I will continue to give a balanced view from the other side of the fence whenever some misguided soul erroneously implies that inserted tooling or QCTPs are easily replaceable when the truth is that needs vary and that there is always space for tooling which fulfils your needs.

    Some people will get by with tooling with severe limitations which can't then be quickly and easily be swapped to an alternate, these are most likely to be the amateurs with amateur equipment that you seem to hold in such contempt :D
     
  7. Aug 21, 2016 #7

    Nick Hulme

    Nick Hulme

    Nick Hulme

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    Make an under or over-length tool holder that can be used as a fixture to align a section of square tool steel with the new holder for pressing.
    Loosely align to the tool holder with a shaft through the tool-post mounting holes of holder and fixture.
    Press the work hot to reduce the force and improve metal flow, a No.3 fly press would probably ease and speed the process.
     
  8. Aug 21, 2016 #8

    Niels Abildgaard

    Niels Abildgaard

    Niels Abildgaard

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    I am an amateur myself and hate being fleeced by smart merchants selling superfluos and overpriced goods.
    Making something better myself is more fun,
    The almost square 2mm carbide holder is finished and ready for testing/comparing on a Myford.
    Free and with no obligation but words and pictures.
    It has already demonstrated to me that the differential closing screw is to powerfull and an overkill.
    Send me a mail with postal adress and it goes of tomorrow.
    Only limitt is that Future users/testers have either diamond or Carborundum for sharpening.
    Corund will not do.

    WP_20160821_010[1].jpg
     
  9. Aug 22, 2016 #9

    Nick Hulme

    Nick Hulme

    Nick Hulme

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    Niels,
    They're a great tool, the design is good, the concept is well proven, provided the user sharpens them correctly they will perform flawlessly.
    If you start with a fixture or a round hole and hot press for your square holder I'm sure you'll get a neater aperture.
    Let me know when you do one that will fit in a QCTP holder ;-)

    - Nick
     
  10. Aug 28, 2016 #10

    Jdunbar

    Jdunbar

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    Niels

    I made one of your tools several years ago. This quickly became my favorite tool. The only thing I dislike about the tool holder is taking the bit out to sharpen and reset the height. It is the version that a screw runs inside the holder and pulls the bit back against the holder to keep the bit in place. It is very rigid and never slips, but I have to remove the bolt that holds the tool holder to the top slide to access the screw. Can you please further explain how you are using two different thread pitches to tighten the bit.

    Thank you

    John Dunbar
     
  11. Aug 28, 2016 #11

    Niels Abildgaard

    Niels Abildgaard

    Niels Abildgaard

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    Hello John
    My present favourite way of manufacture is more or less shown here:

    http://www.homemodelenginemachinist.com/showthread.php?p=229361#post229361

    It is working to owners satisfaction near Seattle

    The differential clamping system parts are shown on sketch and photo.
    The red screw is a normal M8 countersunk Unbrako where head has been threaded UNF 3/8.
    M8 has a pitch of 1,25 mm and 3/8 Unf has ca 1.05.
    Resulting thigtening is thus .2mm per turn.
    The pink M8 nut is secured with a M5 grub screw (blind threaded hole) and goes nowhere.
    The holder shown is a not perfect prototype and the differential system it is really to powerful.
    The tool slot keeps on deforming.
    Its for a Myford and base needs a material with a higher elasticity limit.
    The holder shown had material from a scrap bin at the local farm machine mechanic.
    16MnCr5 will be much better and nice to work as well.

    2  differential.jpg

    WP_20160828_002[1].jpg
     
  12. Aug 28, 2016 #12

    DJP

    DJP

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    I'm not sure why this design needs to have a removable carbide cutter. A simpler holder with the carbide brazed in position might be cheaper and work just as well. Just curious if you have considered this approach.
     
  13. Aug 28, 2016 #13

    Niels Abildgaard

    Niels Abildgaard

    Niels Abildgaard

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    Hello DJP

    Have never considered brazed carbide.
    A 3mm round 65 mm long piece of carbide can be reground 200 times and cost 3 €.
    It takes ca 3 minutes every time.
    The almost square 2 times 2 mm cost much more but is even faster to redress.
    Tool rigidity is also much better in my system.
    Picture shows my newest suitable for a 920 lathe.

    WP_20160828_011[1].jpg
     
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  14. Aug 28, 2016 #14

    mcostello

    mcostello

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    A commercially made brazed carbide tool bit can also be used.
     
  15. Aug 28, 2016 #15

    Jdunbar

    Jdunbar

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    Thanks Niels, the drawing is very helpful. I am going to try this design.

    John Dunbar
     
  16. Aug 29, 2016 #16

    Niels Abildgaard

    Niels Abildgaard

    Niels Abildgaard

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    Hello John

    It is a pleasure that You will make another tangential holder.
    How high is the holder going to be?Square or round?What size carbide or HSS?
    My Boxford is 25.14mm, a Myford I know is 16.6mm ,the latest 920 holder is 22.6mm.
    Below 20mm the 2mm almost square or 3 mm round is rigth.The Myford 16.6 mm is a borderline case as I have no source of 1.5mm round or square carbide.
     
  17. Sep 4, 2016 #17

    Jdunbar

    Jdunbar

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    I have a Southbend 10K, which I believe is very similar to the Boxford. I prefer to use HSS bits because I can get a really nice edge easily. Thanks for the help.

    John Dunbar
     
  18. Sep 16, 2016 #18

    bazmak

    bazmak

    bazmak

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    Many thanks to Niels for supplying me with 2 pieces of solid carbide
    I have made 2 toolholders for the Sieg but I made them to mount in the 4 way toolpost.I had problems with the post being unable to swing with tool projecting to the underside.I then realized that the toolholder need not mount in the toolpost but could become itself a 1 way toolpost.I started with a piece of 40mm sq bar and proceeded to machine more in line with Niels design
    I cut the 4mm dia carbide x 60lg in half and fixed only with a grubscrew
    rather than a split clamp.Trial and error I machined a no of angles and facets
    until I got where I wanted.First impressions are very good.With a 1mm deep cut in MS the finish is excerlent and I can swing the tool around.With in the the correct posn I can turn and face.Time will tell.Next I will make one using the 2mm sq carbide.Many thanks Niels for sending me down this pathe



    [ame]https://www.youtube.com/watch?v=PywupZyd4iM[/ame]
     
  19. Sep 16, 2016 #19

    bazmak

    bazmak

    bazmak

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    Photos of the tool pos[​IMG][[​IMG]/URL]t[​IMG][​IMG]
     
  20. Sep 16, 2016 #20

    Niels Abildgaard

    Niels Abildgaard

    Niels Abildgaard

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    Hello Bazmak and Your are wellcome in the magic circle of non QCTP believers when You are ready.
    Your 4 mm round carbide can cut 2 mm deep before swarf misbehaves,but You can also run it much faster and/or more aggressive feed.
    Look forward to see Your almost square 2 mm version at work.

    If someone want to try my gospel You can either have the complete Myford set shown or one of the 3 sets of 3mm round and 2mm almost square.
    The grinding jig rigth in picture amases me everytime I use it for making almost squares or chamfering the cutting edge to be.
    Price is:
    You do a little writing and a video when ready.
    Do not even dream of putting it in some form of QCTP
    Donate at least 25£ to animal welfare.
    Not Your own dog or cat.

    [ame]https://www.youtube.com/watch?v=DeFLeNPhqDY[/ame]

    WP_20160916_002[1].jpg
     

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