Results 1 to 11 of 11
  1. #1
    Join Date
    Jun 2010
    Location
    Canberra
    Posts
    1,090

    Default Drawbar not drawing straight :(

    If I mount my MT5-ER32 collet chuck in my lathe by just bashing the face with a hammer and a block of wood, I get 0.02mm runout on the inside face of the taper for the collet. However if I fit my drawbar first and use it to draw the chuck in and tighten it, I get 0.05mm runout.

    So if I want the best precision, it seems I'm best off hammering the chuck in place first, then securing it with the drawbar. Does this sound normal, or am I not tightening the drawbar enough, or is my drawbar not pulling straight?

  2. #2
    Join Date
    Jun 2007
    Location
    sydney ( st marys )
    Age
    60
    Posts
    4,296

    Default

    I would not be bashing it in from the front, I would be using the drawbar to hold it in the spindle taper from the word go.

    The draw bar should not have any effect on your chuck running out , not being able to know exactly how you use your draw bar I couldn't comment on the torque need to hold the chuck correctly in the spindle taper.

    As it is just a male MT5 going into a female MT5 it should read the same wether you bash it in and then use the draw bar or just pull it into the spindle taper with the draw bar.

    May be there might be an issue with the chuck.

  3. #3
    Join Date
    Sep 2012
    Location
    North Yorkshire UK
    Posts
    2,860

    Default

    Hi Guys,

    I would make sure that the inside of the spindle is clean and there are no scars !

    I use a 50 mm diameter pin spanner to tighten the ER32 collet chuck drawbar. Over tightening just makes it harder to release it.
    Best Regards:
    Baron J.

  4. #4
    Join Date
    Dec 2013
    Age
    52
    Posts
    581

    Default

    The drawbar should pull it in enough to seat it properly, the taper should seat on it's own as others have said.
    Using Tapatalk

  5. #5
    Join Date
    Sep 2012
    Location
    North Yorkshire UK
    Posts
    2,860

    Default

    Hi Dave,

    Quote Originally Posted by Dave J View Post
    The drawbar should pull it in enough to seat it properly, the taper should seat on it's own as others have said.
    I agree it should ! But if you are getting variations in runout, something is causing the change.
    Best Regards:
    Baron J.

  6. #6
    elanjacobs is online now Apprentice gear maker and machine doctor
    Join Date
    Aug 2008
    Location
    Melbourne
    Age
    29
    Posts
    236

    Default

    Do you get the same runout for each method every time, or does it vary? Perhaps try mounting the chuck in various orientations relative to the spindle and see what kind of repeatability you're getting. It may simply be compound tolerance errors from the 2 surfaces.

  7. #7
    Join Date
    Jun 2010
    Location
    Canberra
    Posts
    1,090

    Default

    Thanks to everyone who's responded - just wanted to check I wasn't getting some fundamental aspect wrong. Each time I've mounted the chuck, I've carefully wiped the inside of the spindle taper and the outside of the chuck taper by hand - both are pretty much immaculate - no dings or scratches. Yet.

    I made the drawbar from some 22mm round bar and added nut made with 2" round BMS, with a reduced section and flats to take a 36mm spanner. The drawbar has a standard M20 thread for the chuck and a fine M20 thread for the nut. With the drawbar and nut screwed into the chuck, there's a fair bit of mass hanging off the back of the chuck, making me think this might be the source of the runout. None of that mass is there if I just tap the chuck into place before screwing in the drawbar.

    That said, it's possible that measuring off the inside of the collet taper may not be the best approach. I'm wondering if I should mount some kind of smooth bar in a collet and take measurements off that.

  8. #8
    Join Date
    Dec 2013
    Age
    52
    Posts
    581

    Default

    Make sure your new drawbar theads are not a perfectly tight fit, as in class of fit to give a little movement.
    Never measure of the outside of a collet chuck, always mount a clean drill shank or end mill in a collet and put a dial indicator on that after it's tightened properly.
    Using Tapatalk

  9. #9
    Join Date
    Jun 2010
    Location
    Canberra
    Posts
    1,090

    Default

    Had another go this morning. Used the shaft of a 5/8" endmill to read off. The readings were better, but showed the same pattern. If I used the drawbar to seat the taper, I got 0.01mm runout. I did about 4 repetitions of releasing the chuck from the MT5 taper, rotating it a little and re-seating it with the drawbar, and never got better than 0.01mm.

    I then dismantled the drawbar, removed the collet and just tapped the chuck into place with a wooden block and hammer, then re-chucked the endmill and there was virtually no movement in the needle.

    While there is still a bit of slop in my drawbar's fit when fully screwed into the chuck, I might try threading it in less to allow more movement, just in case it is pulling it to one side.

  10. #10
    elanjacobs is online now Apprentice gear maker and machine doctor
    Join Date
    Aug 2008
    Location
    Melbourne
    Age
    29
    Posts
    236

    Default

    What are you making that you need better than 0.01??

  11. #11
    Join Date
    Jun 2010
    Location
    Canberra
    Posts
    1,090

    Default

    Quote Originally Posted by elanjacobs View Post
    What are you making that you need better than 0.01??
    Nothing really, but I can confidently get close to zero every time by tapping it in. The drawbar is less predictable, and I'm trying to work out why.

Similar Threads

  1. A simple CAD drawing request
    By jhovel in forum GENERAL DISCUSSION / OFF TOPIC
    Replies: 4
    Last Post: 13th Jul 2017, 11:23 PM
  2. Machinists screw jack drawing
    By bollie7 in forum METALWORK GENERAL
    Replies: 3
    Last Post: 5th Jul 2013, 08:50 AM
  3. Need help with a Chuck Drawing
    By SurfinNev in forum METALWORK GENERAL
    Replies: 20
    Last Post: 25th Jul 2012, 07:49 AM
  4. Trouble attaching a drawing
    By neksmerj in forum METALWORK GENERAL
    Replies: 18
    Last Post: 12th Dec 2010, 07:17 AM
  5. technical drawing
    By tanii51 in forum METALWORK GENERAL
    Replies: 6
    Last Post: 1st Dec 2009, 06:56 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •