Need Help! Lost drill hole size accuracy in drilling operations


Page 1 of 3 123 LastLast
Results 1 to 12 of 28

Thread: Lost drill hole size accuracy in drilling operations

  1. #1
    Member
    Join Date
    Feb 2015
    Posts
    8
    Downloads
    0
    Uploads
    0

    Default Lost drill hole size accuracy in drilling operations

    Hello everyone,

    Some months ago I've been drilling pin holes (6mm) with very tight accuracy.
    The pins were just sliding into the holes smoothly.

    But on the last job I've lost that tight size tolerance and now the drill holes are way looser than before.
    Even with new drill bit (from the same brand).
    Now I need to use 6.2mm pin in order to fit nicely in a hole drilled with 6mm twist drill.
    It wasn't the case before when I was using 6mm pins for a holes drilled with 6mm drill and the fit was almost perfect.

    I've tried drilling with a drill chuck holder and also with a TTS ER collet holder, the result was the same.
    Not even close to the tolerances from few weeks ago.

    Here is a link to some videos that I've made measuring the run out of the tools.
    https://drive.google.com/folderview?...BkV4RzQDa6q3gm
    Please let me know if you have any problems viewing the videos.
    The scale on the indicator is in mm, 0.01mm

    Could you please advice what would be the reason for loosing that accuracy.
    What should I do to fix it.

    Machine is Tormach PCNC 1100 and we're working mainly with steel and aluminum.

    Thanks a lot!

    Similar Threads:


  2. #2
    Member popspipes's Avatar
    Join Date
    Jun 2014
    Location
    United States
    Posts
    1462
    Downloads
    0
    Uploads
    0

    Default Re: Lost drill hole size accuracy in drilling operations

    drilled holes are not very accurate, I would put in another op and ream to 6mm.

    drilled holes depend on how the end is ground, a bit off center and it will drill oversize.

    mike sr


  3. #3
    Member
    Join Date
    Feb 2015
    Posts
    8
    Downloads
    0
    Uploads
    0

    Default Re: Lost drill hole size accuracy in drilling operations

    Quote Originally Posted by popspipes View Post
    drilled holes are not very accurate, I would put in another op and ream to 6mm.

    drilled holes depend on how the end is ground, a bit off center and it will drill oversize.
    Thank you for the reply.
    I do understand that, it was accurate enough for my purpose and now the holes are way oversized.
    I've also tried to drill with 5.7mm and then use 6mm reamer. That didn't produce better result. Still too oversized for 6mm pins.
    Can't figure out what is different now unless there is some tool holder run out, as I mention even with 6mm drill only the tolerance was good for my purpose.



  4. #4
    Member Steve Seebold's Avatar
    Join Date
    Mar 2009
    Location
    USA and proud of it
    Posts
    1872
    Downloads
    0
    Uploads
    0

    Default Re: Lost drill hole size accuracy in drilling operations

    What material are you drilling? What are your feeds and speeds? What is your peck depth? Did you change the brand of drill you are using?

    You can buy GOOD PARTS or you can buy CHEAP PARTS, but you can't buy GOOD CHEAP PARTS.


  5. #5
    Member
    Join Date
    Sep 2005
    Location
    United States
    Posts
    1553
    Downloads
    0
    Uploads
    0

    Default Re: Lost drill hole size accuracy in drilling operations

    Quote Originally Posted by venta7 View Post
    Thank you for the reply.
    I do understand that, it was accurate enough for my purpose and now the holes are way oversized.
    I've also tried to drill with 5.7mm and then use 6mm reamer. That didn't produce better result. Still too oversized for 6mm pins.
    Can't figure out what is different now unless there is some tool holder run out, as I mention even with 6mm drill only the tolerance was good for my purpose.
    Well it used to work fine and now you have some runout or something going on. I would put a dial indicator on your chuck and with the drill bit in the chuck. Try to move the the bit with your fingers or something while the dial indicator present. Rotate by hand with the dial indicator on the bit and etc. Has your drill bit got run out or is it the chuck or perhaps the machine has some wear on the axis?

    Retired Master Electrician, HVAC/R Commercial. FLA Saturn 2 4x4 CNC Router Mach4 Kimber 1911 45ACP


  6. #6
    Member popspipes's Avatar
    Join Date
    Jun 2014
    Location
    United States
    Posts
    1462
    Downloads
    0
    Uploads
    0

    Default Re: Lost drill hole size accuracy in drilling operations

    Quote Originally Posted by venta7 View Post
    Thank you for the reply.
    I do understand that, it was accurate enough for my purpose and now the holes are way oversized.
    I've also tried to drill with 5.7mm and then use 6mm reamer. That didn't produce better result. Still too oversized for 6mm pins.
    Can't figure out what is different now unless there is some tool holder run out, as I mention even with 6mm drill only the tolerance was good for my purpose.
    Another thing is I always spot drill first, takes a bit more time but keeps drill "wander" to a minumim when starting the hole.

    An old mentor showed me a trick to make a drill drill an onsize hole, he just touched the outer edge of the cutting lip with a stone dulling it slightly, this forces the drill to hunt center and makes it drill a tighter hole. I wouldnt have believed it but I was shown and it does work in a pinch.

    mike sr


  7. #7
    Member Don Clement's Avatar
    Join Date
    Jan 2007
    Location
    Running Springs, California USA
    Posts
    1349
    Downloads
    0
    Uploads
    0

    Default Re: Lost drill hole size accuracy in drilling operations

    For locating pin holes I first drill then single point bore and then using this floating reamer holder I built using a 3/8" TTS holder ream to size.

    Don

    Lost drill hole size accuracy in drilling operations-img_7942web-jpg



  8. #8
    Member
    Join Date
    Sep 2005
    Location
    United States
    Posts
    1553
    Downloads
    0
    Uploads
    0

    Default Re: Lost drill hole size accuracy in drilling operations

    Folks he's using a CNC machine, he does not need to spot drill and it all worked fine before.

    Retired Master Electrician, HVAC/R Commercial. FLA Saturn 2 4x4 CNC Router Mach4 Kimber 1911 45ACP


  9. #9
    Member popspipes's Avatar
    Join Date
    Jun 2014
    Location
    United States
    Posts
    1462
    Downloads
    0
    Uploads
    0

    Default Re: Lost drill hole size accuracy in drilling operations

    Quote Originally Posted by wmgeorge View Post
    Folks he's using a CNC machine, he does not need to spot drill and it all worked fine before.
    If the surface is dead flat, and using a web thinned drill, or preferably a screw machine drill no need to spot drill.

    mike sr


  10. #10
    Member popspipes's Avatar
    Join Date
    Jun 2014
    Location
    United States
    Posts
    1462
    Downloads
    0
    Uploads
    0

    Default Re: Lost drill hole size accuracy in drilling operations

    Quote Originally Posted by Don Clement View Post
    For locating pin holes I first drill then single point bore and then using this floating reamer holder I built using a 3/8" TTS holder ream to size.

    Don








    Lost drill hole size accuracy in drilling operations-img_7942web-jpg
    I like your floating reamer holder!, may try to make one for myself......
    I also like your indicator holder that fits in the spindle with a dovetail assembly at 90 degrees, I have looked on ebay etc but havent found one like yours, very good idea Don

    mike sr


  11. #11
    Member
    Join Date
    Jan 2005
    Location
    USA
    Posts
    10012
    Downloads
    0
    Uploads
    0

    Default Re: Lost drill hole size accuracy in drilling operations

    Quote Originally Posted by wmgeorge View Post
    Folks he's using a CNC machine, he does not need to spot drill and it all worked fine before.
    It does not matter what the machine is CNC or a manual Drill Press a Spot drill is always needed unless the Drill bit is designed to be used without a Spot Drill, there are some quality Drills that are ground so a Spot Drill is not needed, I would say he got lucky with his hole sizes before, a drill Bit unless you know how to grind it can make any size hole you want, over size or on size

    Using the Drill Chuck that he has is never going to be very accurate, these drills are some of the best there are if he wants a quality drill Wedevag that will drill on size if his spindle and holder runout is very low and he would need to be using a Screw Machine Drill

    North Bay Cutting Tools

    Or Ebay https://www.ebay.com/itm/3906-25-64-...ss!37179!US!-1

    Mactec54


  12. #12
    Member
    Join Date
    Dec 2015
    Posts
    386
    Downloads
    0
    Uploads
    0

    Default Re: Lost drill hole size accuracy in drilling operations

    "got lucky"

    That's my assessment too. I think OP got above average results and is now getting the results we all would have expected.

    In a pinch I've milled/bored pockets with an end mill using a helical path then hit them with a drill as sort of a make shift reamer. This generally is only useful for deep holes where an end mill would't be practical or if you don't have a spot drill. It does provide nice results. The added benefit is it greatly reduces the amount of chip evacuation during drilling and the surface finish can be quite nice as a result.



Page 1 of 3 123 LastLast

Tags for this Thread

Posting Permissions

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


About CNCzone.com

    We are the largest and most active discussion forum for manufacturing industry. The site is 100% free to join and use, so join today!

Follow us on


Our Brands

Lost drill hole size accuracy in drilling operations

Lost drill hole size accuracy in drilling operations