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  1. #41
    Join Date
    Mar 2015
    Posts
    409

    Re: would you buy this machine?

    If the tailstock is to low, you could shim it using aluminum foil. If it very low, shim it using epoxy. Oil the top half so it can be loosened again. You will probably don't be able to ajust it for turning small tapers.

    If you just need to scrape a few 0.01 mm on planes that don't slide, use a small diamond disk (dremel) and "scrape" it by hand (don.t use the dremel, just the disk). I did the same for adjusted the head stock of both my lathes. It will take a few hours, but who cares.

  2. #42
    Join Date
    Nov 2014
    Posts
    75
    Very interesting!! The biggest problem i think is the cross slide that is very stiff in one place and normal to another...what did you use as a surface plate and straight edge? My lathe has a worn bed 0.08mm from what i measured
    Quote Originally Posted by hfjbuis View Post
    If the tailstock is to low, you could shim it using aluminum foil. If it very low, shim it using epoxy. Oil the top half so it can be loosened again. You will probably don't be able to ajust it for turning small tapers.

    If you just need to scrape a few 0.01 mm on planes that don't slide, use a small diamond disk (dremel) and "scrape" it by hand (don.t use the dremel, just the disk). I did the same for adjusted the head stock of both my lathes. It will take a few hours, but who cares.

  3. #43
    Join Date
    Mar 2015
    Posts
    409

    Re: would you buy this machine?

    The headstock of my lathe (s) were not aligned. The are bolted to a trapezoide bed. To align the headstock, i had to scrape the trapezoidal bottom of the head stock. It took me about 4 hours to get the alignment within 0.01 mm measured over 100 mm distance. So I hadn't to remove a lot of material and uses a dremel diamond grinding disk. To decide where to grind, i made the bottom of the tailstock black using a pental pen and grinded only the high spots.
    The second problem was to carriage of both lathes. I could rock the edges about 0.03 mm. So i grinded the other 3 sides the same way as the headstock until it was flat. After the carriage was done, I polished the bottom using the dremel, polish brush and polish paste. I am sure scraping would be better but I haven't a scraper or large straight surface to check. For my hobby use, I am very satisfied with the result.

    If you can measure the worn of the bed, than maybe you can use this measurement to straighten the bed. Even if you don't get it a 100 %, even a bit better will be worth a try.

    Here in the Netherlands there are some companies that will straighten the bed. This will cost a lot more than a new Chinese lathe (both my lathes are Chinese).

    When I need a straight surface, I use the mill table or the bed (unused part) of the lathe.

  4. #44
    Join Date
    Nov 2014
    Posts
    75
    I will try to do the same as you did using the minj lathe bed!hooe it works...evebtually i will need the tools but till then i have to try it...many conglatulations on you success!!
    Quote Originally Posted by hfjbuis View Post
    The headstock of my lathe (s) were not aligned. The are bolted to a trapezoide bed. To align the headstock, i had to scrape the trapezoidal bottom of the head stock. It took me about 4 hours to get the alignment within 0.01 mm measured over 100 mm distance. So I hadn't to remove a lot of material and uses a dremel diamond grinding disk. To decide where to grind, i made the bottom of the tailstock black using a pental pen and grinded only the high spots.
    The second problem was to carriage of both lathes. I could rock the edges about 0.03 mm. So i grinded the other 3 sides the same way as the headstock until it was flat. After the carriage was done, I polished the bottom using the dremel, polish brush and polish paste. I am sure scraping would be better but I haven't a scraper or large straight surface to check. For my hobby use, I am very satisfied with the result.

    If you can measure the worn of the bed, than maybe you can use this measurement to straighten the bed. Even if you don't get it a 100 %, even a bit better will be worth a try.

    Here in the Netherlands there are some companies that will straighten the bed. This will cost a lot more than a new Chinese lathe (both my lathes are Chinese).

    When I need a straight surface, I use the mill table or the bed (unused part) of the lathe.

  5. #45
    Join Date
    Aug 2009
    Posts
    230

    Re: would you buy this machine?

    Disclaimer: I am not a machine restoration expert; nor do I play one on TV.

    However, some things do come to mind:

    First, if you aren't already subscribed to Kieth Rucker's YouTube channel; you should check it out. Amongst other things, he does machine rebuilding. Ox Tools is another good one, too...
    https://www.youtube.com/user/ksruckerowwm
    https://www.youtube.com/user/oxtoolco

    If you don't already have it, get some high-spot bluing compound.

    Supposedly, float glass is really flat; and sometimes you can find granite tile that's very flat also (although, when you are talking about one that's tile-sized; a proper granite surface plate isn't that expensive). Take three pieces and compare them against each other with the bluing compound - the only contact surface that can be common between three pieces like that is a flat plane. Not only can you use this principal to verify the plate's flatness; but you can also make them more flat by putting lapping compound on them and alternately rubbing them against each other (1 against 2, 1 against 3, and then 2 against 3). It is labor intensive; but it does work. Come to think of it; I might even get a small gear motor (like perhaps a windshield wiper motor off of a truck, er, lorry) to do the rubbing for me.


  6. #46
    Join Date
    Jun 2010
    Posts
    4252

    Re: would you buy this machine?

    It is beginning to look very nice now.

    Cheers
    Roger

  7. #47
    Join Date
    Nov 2014
    Posts
    75
    Yeap totaly agree with you with everything said...but isnt my chineese lathe bed more accurate than float glass or granite tile?
    Quote Originally Posted by __Britt View Post
    Disclaimer: I am not a machine restoration expert; nor do I play one on TV.

    However, some things do come to mind:

    First, if you aren't already subscribed to Kieth Rucker's YouTube channel; you should check it out. Amongst other things, he does machine rebuilding. Ox Tools is another good one, too...
    https://www.youtube.com/user/ksruckerowwm
    https://www.youtube.com/user/oxtoolco

    If you don't already have it, get some high-spot bluing compound.

    Supposedly, float glass is really flat; and sometimes you can find granite tile that's very flat also (although, when you are talking about one that's tile-sized; a proper granite surface plate isn't that expensive). Take three pieces and compare them against each other with the bluing compound - the only contact surface that can be common between three pieces like that is a flat plane. Not only can you use this principal to verify the plate's flatness; but you can also make them more flat by putting lapping compound on them and alternately rubbing them against each other (1 against 2, 1 against 3, and then 2 against 3). It is labor intensive; but it does work. Come to think of it; I might even get a small gear motor (like perhaps a windshield wiper motor off of a truck, er, lorry) to do the rubbing for me.


  8. #48
    Join Date
    Nov 2014
    Posts
    75
    Thanks alot! I really like it too!Much time spent on thia oroject and it is not done yet...if i find a way i will scrape the parts needed to become better!
    Quote Originally Posted by RCaffin View Post
    It is beginning to look very nice now.

    Cheers
    Roger

  9. #49
    Join Date
    Aug 2009
    Posts
    230

    Re: would you buy this machine?

    but isnt my chineese lathe bed more accurate than float glass or granite tile?
    Depends on how much it's been used; and how good it was leaving the factory. It could be... however, if you are cross-checking them all against each other, you will know for sure. Of course, out-of-the-box, nothing from the home improvement center is going to beat a proper metrology-grade reference surface...

    The glass & tile was only suggested because they are cheap; not because they are optimum for the application.


  10. #50
    Join Date
    Nov 2014
    Posts
    75
    Hi there!I have tried and found glass beforre but was not flat at all...maybe we dont have float glass where i live..i will post back the results as soon as i read the machine reconditioning and scraping book
    Quote Originally Posted by __Britt View Post
    Depends on how much it's been used; and how good it was leaving the factory. It could be... however, if you are cross-checking them all against each other, you will know for sure. Of course, out-of-the-box, nothing from the home improvement center is going to beat a proper metrology-grade reference surface...

    The glass & tile was only suggested because they are cheap; not because they are optimum for the application.


  11. #51
    Join Date
    Jun 2010
    Posts
    4252

    Re: would you buy this machine?

    Ah well, what you buy for windows is NOT float glass. I am not sure what it is called, but it wobbles everywhere.
    I have what I think is one piece of float glass, but I cannot see how I could use it to check the bed on my lathe, There are two ridges there. What really matters is how well the saddle rides on the bigger of those two ridges.

    Cheers
    Roger

  12. #52
    Join Date
    Nov 2014
    Posts
    75
    Yes i have the one for windows haha....it is bent all over!I will upload a video so as to see the current problems of the lathe!
    Quote Originally Posted by RCaffin View Post
    Ah well, what you buy for windows is NOT float glass. I am not sure what it is called, but it wobbles everywhere.
    I have what I think is one piece of float glass, but I cannot see how I could use it to check the bed on my lathe, There are two ridges there. What really matters is how well the saddle rides on the bigger of those two ridges.

    Cheers
    Roger

  13. #53
    Join Date
    Aug 2009
    Posts
    230

    Re: would you buy this machine?

    The idea is supposed to be that you use it as a reference surface to blue the bed against... basically as a substitute for a granite or cast-iron straight-edge. I figure that it would need a backing support frame to keep it from flexing; and you would definitely need to do the three pieces test/correction to get it spot-on... and watch out for thermal effects that could curve the surface.

    Again; this is just what I've read elsewhere; not from personal experience... and it's not suggested as good or easy or expedient in a commercial setting... just cheap.


  14. #54
    Join Date
    Nov 2014
    Posts
    75
    Hi there!So i have bought alla the electronic parts for an electronic leadscrew...Fist of all i would like to ask...is there a way to make threads if you attach a servo o the kathe feed screw?Remeber this kathe does not have a leadscrew..only a feedscrew...i will also post pictures to tell me of there is a simple way to attach the sensor to the spindle

  15. #55
    Join Date
    Nov 2014
    Posts
    75
    I am going to try this idea...maybe you can tell me how you designed the air spring and the plans
    Quote Originally Posted by Jim Dawson View Post
    That should be enough torque. I am using 11.2Nm (29Nm peak) servos on my lathe, and the carriage masses about 600Kg. Acceleration is very good with 400 IPM rapids. My lathe is a medium sized slant bed with a 10 tool turret, 7.5 KW spindle.



    Rather than use a ball screw, it is possible to use the original carriage drive (not the lead screw) if you use linear encoders and an air spring to control the backlash. This way you can use the lathe as both manual and CNC with an instant change over. I designed this system for my manual lathe, but never built it because I bought a CNC lathe. I designed this system because I wanted both manual and CNC capability. I know the air spring works because I am using a similar system to control the backlash on the Z axis of my mill.

    To use in manual mode, just de-couple the servo from the normal lathe drive, shift it into neutral when using in CNC mode. An automotive air conditioner clutch would work well for this, they will transmit a lot of torque.

  16. #56
    Join Date
    Mar 2015
    Posts
    409

    Re: would you buy this machine?

    Quote Originally Posted by pikolo View Post
    Hi there!So i have bought alla the electronic parts for an electronic leadscrew...Fist of all i would like to ask...is there a way to make threads if you attach a servo o the kathe feed screw?Remeber this kathe does not have a leadscrew..only a feedscrew...i will also post pictures to tell me of there is a simple way to attach the sensor to the spindle
    A lead screw is a bit more accurate than a feed screw. Due to the bronze nut, it is also more fragile. So it is still usable for threading.
    On the picture below is the setup for the spindle sync (threading) sensors. Basically you only need one spindle sync pulse. If your spindle drive is low on torque (like mine), you can benefit from extra speed synchronization pulses. If your controller support this (I use GRBL) you could add a speed synchronization pulse sensor and some magnets on the spindle. I have added 8 magnets on my spindle. If you do, make sure the index magnet is located in the mid of the speed synchronization magnets.
    If your controller supports it, you could also use an encoder some how coupled (1:1) to the spindle.
    I glued the magnets on a aluminum bus that is screwed on the back of the spindle. Just to start, you could also tape the spindle sync pulse magnet to the spindle.

    I use NJK-5001C NPN NO sensors, the 5V version.

  17. #57
    Join Date
    Nov 2014
    Posts
    75
    This looks like the chineese mini lathe
    I have another codec from clogh 42 videos....but can i add it to the feed screw?
    Quote Originally Posted by hfjbuis View Post
    A lead screw is a bit more accurate than a feed screw. Due to the bronze nut, it is also more fragile. So it is still usable for threading.
    On the picture below is the setup for the spindle sync (threading) sensors. Basically you only need one spindle sync pulse. If your spindle drive is low on torque (like mine), you can benefit from extra speed synchronization pulses. If your controller support this (I use GRBL) you could add a speed synchronization pulse sensor and some magnets on the spindle. I have added 8 magnets on my spindle. If you do, make sure the index magnet is located in the mid of the speed synchronization magnets.
    If your controller supports it, you could also use an encoder some how coupled (1:1) to the spindle.
    I glued the magnets on a aluminum bus that is screwed on the back of the spindle. Just to start, you could also tape the spindle sync pulse magnet to the spindle.

    I use NJK-5001C NPN NO sensors, the 5V version.

  18. #58
    Join Date
    Mar 2015
    Posts
    409

    Re: would you buy this machine?

    Quote Originally Posted by pikolo View Post
    This looks like the chineese mini lathe
    Yes, it is the first lathe I have bought some 10 years ago. It is a HBM 300 DC lathe (300 mm 500 W). I have the same setup on my second lathe (HBM BF290,700mm 1.5kW).
    have another codec from clogh 42 videos....but can i add it to the feed screw?
    De type of decoders (codec) you can use, depends on the controller you have.
    What "codec" do you have?
    What controller do you have?

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