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  1. #1
    Join Date
    Mar 2011
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    Taree NSW
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    119

    Default why cant I cut this thread?

    I have a Takisawa 1000D lathe and am attempting to cut a 16 TPI thread - I have the proper gears assembled in the gear train as shown on the info plate and the levers for threading in the appropriate position but cant seem able to cut 16 TPI
    The thread chasing dial shows 24,21,20 and 18 and the appropriate alphabetical position to engage the dial - I cant understand why I cant engage anywhere as the sprocket engaging the leadscrew (24T) engages the fixed TPI leadscrew - does the fact that the chasing dial has only the numbers above mean I can only engage 24,21, 20 or 18 TPI? I am sure I haven't had this problem before so maybe I'm missing something?

  2. #2
    Join Date
    Aug 2008
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    near Rockhampton
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    Default

    I am a bit confused by your description.

    If you have a metric leadscrew lathe, you can not use the thread chasing dial for an imperial thread.
    Gold, the colour of choice for the discerning person.

  3. #3
    Join Date
    Mar 2011
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    Taree NSW
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    Default

    O.K. so how do I cut 16 TPI thread?

  4. #4
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    Aug 2008
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    near Rockhampton
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    Default

    Also you are aware with metric chasing dials, you need different gears for the dial itself for different metric pitches.

    Metric threading on a lathe is not as straight forward as native imperial threading
    Gold, the colour of choice for the discerning person.

  5. #5
    Join Date
    Jul 2013
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    BRISBANE BAYSIDE
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    90

    Default

    Forget about the thread chasing dial.
    Engage the half nuts, take the first pass but stop the lathe at the end of the thread. (it helps to have a groove here just marginally deeper than the thread depth)
    Back off the tool a little, then reverse the lathe till the tool clears the end of the thread.
    Wind in the tool for a bit more cut and then proceed as for the first cut until you have cut the thread full depth.
    DO NOT DISENGAGE the half nuts until you have finished cutting the thread.
    The only tricky bit is stopping the lathe at the end of the thread. Use the lowest speed you have available as this gives the most reaction time.
    Works for me.

    Alan.

  6. #6
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
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    6,439

    Default

    Hi Alf, Guys,

    What Alan said !

    What I do different is run the lathe backwards and cut away from the chuck, no danger of hitting anything that way.

    Because I have an imperial lathe I have to keep the half nut engaged when cutting metric threads, exactly the opposite to you.

    18-09-2018-3.JPG 18-09-2018-2.JPG
    This is my setup. Here I'm cutting a 4-48 thread.

    A spindle mandrel would be a good Idea ! I'll do a post on mine later.
    Best Regards:
    Baron J.

  7. #7
    Join Date
    Nov 2017
    Location
    Geelong, Australia
    Age
    57
    Posts
    2,651

    Default

    I've got the same lathe but unfortunately my change gears aren't finished yet so I haven't done any thread cutting.

    Mine has a 4mm pitch leadscrew, and these marks on the chasing dial and the plate next to it.





    To be honest I'm not sure exactly what those markings mean, and doesn't sound like yours is the same.

    Steve

  8. #8
    Join Date
    Jan 2016
    Location
    Wodonga Vic
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    38
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    633

    Default

    You can still use the halfnuts to terminate the thread, you just gotta disengage the halfnut at the end of the thread and kill the motor, withdraw the tool, start the lathe in reverse and pick back up on the same number with the thread dial, make life easy and use position 1 on the tread dial

  9. #9
    Join Date
    Apr 2012
    Location
    Healesville
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    2,129

    Default

    Quote Originally Posted by OxxAndBert View Post

    To be honest I'm not sure exactly what those markings mean, and doesn't sound like yours is the same.

    Steve
    The numbers at the top are the number of gear teeth for the gear that goes on the bottom of the chasing dial that engages the lead screw, and beneath each of the numbers is the pitch of the threads that work with those gears to synchronize the dial with the thread that you are cutting.
    The letters I assume ? relate to the thread cutting g/box, just a guess tho...
    cheers,shed

  10. #10
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    Nov 2017
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    Geelong, Australia
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    Default

    Quote Originally Posted by shedhappens View Post
    The numbers at the top are the number of gear teeth for the gear that goes on the bottom of the chasing dial that engages the lead screw, and beneath each of the numbers is the pitch of the threads that work with those gears to synchronize the dial with the thread that you are cutting.
    The letters I assume ? relate to the thread cutting g/box, just a guess tho...
    cheers,shed
    Thanks Shed -I hadn't even thought about there being different chaser gears.
    The letters on the dial look like they match the ones on the chart, but I'm not sure how you get the other letters. Possibly the dial is double sided, but I haven't removed it to check.
    Guessing I'll need to make some chaser gears as well as change gears that are in progress...

    Steve

  11. #11
    Join Date
    Mar 2011
    Location
    Taree NSW
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    Default

    Thanks Steve and guys
    - I have set my change gears as per the imperial threading plate ie. 72,68,30 and 120 then B (LH lever) and and RH lever to the right -have put a 16 TPI bolt in the chuck but the tool does not match the bolt when engaged but according to your second picture I should be engaging at 'E' as my manual says I have a 24 tooth gear engaging with the lead screw - will try again later and report back - dont understand the difference when engaging the chasing dial as the half nut has fixed TPI to match the leadscrew

  12. #12
    Join Date
    May 2015
    Location
    Richmond
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    214

    Default

    Quote Originally Posted by Alf Scotting View Post
    Thanks Steve and guys
    - I have set my change gears as per the imperial threading plate ie. 72,68,30 and 120 then B (LH lever) and and RH lever to the right -have put a 16 TPI bolt in the chuck but the tool does not match the bolt when engaged but according to your second picture I should be engaging at 'E' as my manual says I have a 24 tooth gear engaging with the lead screw - will try again later and report back - dont understand the difference when engaging the chasing dial as the half nut has fixed TPI to match the leadscrew
    It doesn't matter where you engage the half nut TO START when cutting an imperial thread on a metric lathe or VV as it is totally impractical to think we can disengage and use the chasing dial so reversing the spindle is the only way. The chasing dial will only work cutting metric threads. All you will do is progressively chew the thread up by engaging out of pitch UNLESS WE ARE GOOD AT WINNING THE LOTTERY 100% OF THE TIME!!

    Have a look at the calcs I have added. As can be seen, you would have to have a 127 tooth gear or multiple of to successfully track it. For the 6mm leadscrew the repeat distance to drop in is 762mm.

    Hope this will clear up some of your problem. The MAZAK lathes had the same (similar) chasing dial as you have there. We had two of them at work with the same setup. Good machines although I didn't like the carriage hand wheel position!

    Rusty
    Attached Images Attached Images

  13. #13
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    Jun 2011
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    Quote Originally Posted by OldRustyToolie View Post
    It doesn't matter where you engage the half nut TO START when cutting an imperial thread on a metric lathe or VV as it is totally impractical to think we can disengage and use the chasing dial so and reversing the spindle is the only way. The chasing dial will only work cutting metric threads. All you will do is progressively chew the thread up by engaging out of pitch UNLESS WE ARE GOOD AT WINNING THE LOTTERY 100% OF THE TIME!!

    Have a look at the calcs I have added. As can be seen, you would have to have a 127 tooth gear or multiple of to successfully track it. For the 6mm leadscrew the repeat distance to drop in is 762mm.

    Hope this will clear up some of your problem. The MAZAK lathes had the same (similar) chasing dial as you have there. We had two of them at work with the same setup. Good machines although I didn't like the carriage hand wheel position!

    Rusty
    Yeah - IIRC I remember you, Bob or Joe setting up one of the lathes and showing us that 762mm trick many years ago.

    Personally I totally avoid this sort of problem by owning both an inch and a metric leadscrew lathe. Problem solved (at the expense of space/money). And anyway the Monarch CY has a single tooth dog clutch and leadscrew reverse so you don't need to do anything much once you've set the disengaging stop. Pity it's in bits while I re-scrape the cross slide & top slide ways.

    Some idiot wants me to cut a 1/2-13 (UNC) thread ATM. I've just convinced him that 1/2" Whitworth will do fine. I hate cutting threads with prime number pitches, I'd have to look at the manual.....

    PDW

  14. #14
    Join Date
    May 2015
    Location
    Richmond
    Posts
    214

    Default

    No probs Pete. On an imperial machine just engage on inch marks Although my Dashin Prince stuffs that one up! The whole numbers actually relate to 3/4inch spacings on it.

    Bob still kicking in Qld somewhere. Lost Joe a couple of years back due to a fall.

  15. #15
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    Mar 2011
    Location
    Taree NSW
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    Default

    O.K. guys,thanks for your input none of which has solved my problem - I was going to ask Steve if we could talk as he has the same lathe as mine but no change gears so obviously can't cut threads - I have triple checked my settings with my change gears and as I am cutting a stud without a runout groove I always retract the tool at the end and reverse the rotation direction - I just put a 20mm. piece of brass in the chuck, engaged the half nut and took a cut which gave me a groove of about 40 TPI ???My manual tells me the gear engaging the leadscrew is 24T and the panel near the halfnut engagement lever has underneath 24 the letter 'E' so I engaged at 'E' but still get 40ish TPI
    I have cut threads in the past without any problem so keep thinking I have missed something but can't think what it would be - keep thinking please fellers The calculation by old rusty toolie , I can't see its relevance to my problem

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