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Thread: Grinding lathe tools - small concave form / radius

  1. #11
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    Mar 2013
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    I have been having fun grinding lathe tools like this using cheap diamond wheels and burrs in my CNC. I have also been using it with a 4th axis to make special milling cutters from standard ones. With diamond there isn't a ton of grit going all all over like abrasive wheels.

  2. #12

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    Can not easily be done by hand, controlling the tool to produce an accurate radius/arc on a form tool will prove difficult at best.

    Off Topic
    This is how a convex or concave radius is produced in an ancient 1996 CNC lathe, this happens to be a concave radius for a rope sheave, turning a ball is just as easy.


    A finished ball.


    You may make any size radius that you have small enough tooling for.
    The canned cycle on this machine will not turn a ball in one shot for some reason so it takes 2 canned programs, one from the end to 1/2 way and another from 1/2 way to the back, go figure.

    The canned cycle code looks like so for a 1 1/2" ball.

    Tool width .125
    nose radius .062
    Program 1
    Start X 0.000 Z 0.000
    Line move X 1.500 Z -.75 Radius .750
    Line move to the Max stock diameter if larger then 1.500
    Roughing cycle
    DOC .050
    Feed .012
    Finish cycle
    DOC .005
    Feed .004
    End Program
    Program 2
    Start X1.500 Z -.75
    Line move X 0.000 Z -1.500 Radius .750 ( this will cut the ball off leaving a nub from parting"
    Same DOC and Feed rate. You tell the control the shape of the part and it generates the G-Code for you just like CAM.

    Easy as pie, less then a dozen lines entered, any person with manual lathe experience could learn to program canned cycles in short order which are most of the routines a hobbyist will ever need.
    The bad news is that such a control alone will cost several times what a small hobby lathe costs, such a Fanuc, Mazatrol and Hardinge. I suspect that this is why many low priced CNC machine manufacturers use Mach 3.

    Do not be afraid of CNC, you probably did not know how to use a lathe when you started, same thing using a different method of control (-:
    Last edited by Bented; 08-12-2019 at 10:47 PM.

  3. #13
    Join Date
    Dec 2016
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    Quote Originally Posted by BCRider View Post
    You need ONE new ball handle? Why not just cut the ball by eye and file to shape by eye? Or if you must have it be a specific size to match make a little template that you can hold in a mag base arm just behind the stock and machine steps in the stock to rough form the basic ball and then file to shape and check the progress repeatedly with the template.
    Say what?

    At minimum you need TC grinder project + internal/external radius grinding jig +probably diamond wheel balancer project
    Probably leads to building oscilloscope + adjustable bandbass filter for the dynamic balancer and ....

    Ball handle? who needs it after that?

  4. #14
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    Aug 2012
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    Warwickshire, UK
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    The old time toolmakers I knew would simply take an old flat file, heat to red to soften it, drill or mill the required radius/shape, putting the hole it at an angle to get some cutting angle, then reharden and temper. Job done in an hour. I've done it myself and it works. You are not going into production with these after all, just want to do one or two?
    'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger

  5. #15
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    Richard, I like your thinking. This would be particularly good for a small size like the one shown on that control piece.

    Of course now Mattij's anti simplicity rant will be focused on you too....

    ..... now where did I leave that bandpass filter and fragulator bracket........

  6. #16
    Join Date
    Mar 2010
    Location
    Metro Detroit
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    Thank all of you that responded with diamond wheels and burrs. My cheap local tool supplier does not have much of a selection. I'll need to order some to have future options. Also appreciated the heads up on roughing with an abrasive masonry blade.

    I worked the corners of my green wheel an got two tools that were close enough for roughing in the ball stud. Once I silver soldered the stud to the damaged lever, I used both the tools and a file to bring the ball into shape - ready to reassemble.

    Finally, a personal question to MattiJ. For work, I briefly commuted to Trollhattan (not sure how to get umlauts over the first "a") with side trips to Uusikaupunki. I'm well aware how competent most Finns converse in English. Your use of English in your various postings is spot on to US conversation. Do you care to mention a bit about your background? If not, that's OK and sorry to pry.

    Sent from my 5049W using Tapatalk

  7. #17
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    Oct 2002
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    Quote Originally Posted by aribert View Post
    ..........(not sure how to get umlauts over the first "a")..........
    Hold down ALT key while you type in 0228 (on the right side of the keyboard).

  8. #18
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    Metro Detroit
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    Quote Originally Posted by Arcane View Post
    Hold down ALT key while you type in 0228 (on the right side of the keyboard).
    Thanks - good to know. Unfortunately I was typing on the "Droid" to be able to upload the pic via Tapatalk. The Micro USB port on my phone is shot and I am barely able to charge the phone - definitely unable to download with a cable.

  9. #19
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    Quote Originally Posted by aribert View Post
    Finally, a personal question to MattiJ. For work, I briefly commuted to Trollhattan (not sure how to get umlauts over the first "a") with side trips to Uusikaupunki. I'm well aware how competent most Finns converse in English. Your use of English in your various postings is spot on to US conversation. Do you care to mention a bit about your background? If not, that's OK and sorry to pry.
    GM/Saab?

    Thanks, I guess.
    I have learnt my English just by reading internet forums, books and technical literature and chit-chatting on various internet forums.
    I use English daily also at home with my wife (Thai) but I'm not sure who has learnt and what from that.

  10. #20
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    Warwickshire, UK
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    Quote Originally Posted by aribert View Post
    Thank all of you that responded with diamond wheels and burrs. My cheap local tool supplier does not have much of a selection. I'll need to order some to have future options. Also appreciated the heads up on roughing with an abrasive masonry blade.

    I worked the corners of my green wheel an got two tools that were close enough for roughing in the ball stud. Once I silver soldered the stud to the damaged lever, I used both the tools and a file to bring the ball into shape - ready to reassemble.

    Finally, a personal question to MattiJ. For work, I briefly commuted to Trollhattan (not sure how to get umlauts over the first "a") with side trips to Uusikaupunki. I'm well aware how competent most Finns converse in English. Your use of English in your various postings is spot on to US conversation. Do you care to mention a bit about your background? If not, that's OK and sorry to pry.

    Sent from my 5049W using Tapatalk
    Glad you got it sorted without much problem. I would have suggested using the corners of the green grit wheel to work a little radius, checking the result with a radius gauge, having done it myself at times, but thought the howls of protest from the fully equipped toolroom boys would be deafening. I don't know what the UK equivalent of 'Bubba' or 'Shade tree mechanic' is, but whatever it is, I think I'm one. Possibly 'Coal Board Fitter'
    'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger

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