Can problems arise from a drawbar being too long?
Close
Login to Your Account
Results 1 to 10 of 10
  1. #1
    Join Date
    Jun 2019
    Country
    UNITED STATES
    State/Province
    California
    Posts
    4
    Post Thanks / Like
    Likes (Given)
    1
    Likes (Received)
    0

    Default Can problems arise from a drawbar being too long?

    Hi, my company recently bought a new TRAK bed mill which included, among other features, a BT30 taper spindle and power drawbar. However, the drawbar is about 3/8" too long. So in order to engage a tool holder with the drive dogs, you need to line up the threads, screw it on maybe 6 turns, and then engage the power drawbar (or just try to visually line it up and hope you're dead on). The drawbar length is "to spec", the spacer is in place, it's just... too long for this machine. The salesman and TRAK tech support are treating this as a low-priority issue, and suggested some "fixes" I could try. Honestly, for having spent 45 grand on this machine, I'm kinda pissed that this is an issue.

    Apart from being irritating, is this likely to cause problems when we start cutting? The taper seats just fine, and I don't think the drawbar is bottoming out in any of the toolholders.

  2. #2
    Join Date
    Apr 2004
    Location
    Milwaukee,WI
    Posts
    1,276
    Post Thanks / Like
    Likes (Given)
    6885
    Likes (Received)
    994

    Default

    I would shorten the drawbar. On the link scroll down to the last page on the right. You need one of these for a 30 taper. I have one on my 40 taper bedmill and love it.


    https://aceronline.net/acergroup/man...orque-rite.pdf

  3. #3
    Join Date
    Jan 2007
    Location
    Flushing/Flint, Michigan
    Posts
    7,581
    Post Thanks / Like
    Likes (Given)
    377
    Likes (Received)
    6332

    Default

    After dropping 45 large I'd be more than just pissed.
    They give you suggestions? I'd suggest they get a serviceman to come fix it for me.
    Maybe you are doing something wrong but service after the sale counts.
    I get the pointed to guide but at this price tag you should not need "do it your self" add-ons or modifications.
    Bar should be at least one times dia. in engagement min. Above this you get no help but an added 25% is good as threads on both side may not be clean.
    Taller than normal keys are needed to do this and why the factory can't understand that says something.
    The whole point of a power drawbar is quick change with no fiddle farting around. 5-10 seconds, bang/bang go.
    Bob

  4. Likes blue_heron liked this post
  5. #4
    Join Date
    Sep 2005
    Location
    il.
    Posts
    6,632
    Post Thanks / Like
    Likes (Given)
    30
    Likes (Received)
    1213

    Default

    sounds like improper installation of the option to me

  6. #5
    Join Date
    Mar 2019
    Country
    UNITED KINGDOM
    Posts
    143
    Post Thanks / Like
    Likes (Given)
    2
    Likes (Received)
    23

    Default

    Have you got the right tool holders?

    We had a similar problem when I started using a different set of tool holders on a TRAK knee mill, except the draw bar was too short, so we made a longer one.

  7. #6
    Join Date
    Apr 2004
    Location
    Modesto, CA USA
    Posts
    6,731
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    1114

    Default

    Bar should be at least one times dia. in engagement min. Above this you get no help but an added 25% is good as threads on both side may not be clean.


    For normal bolting up operations I always heard the rule of thumb was 1+1/2 bolt diameter thread length of engagement. any more and the bolt would shear before the threads pulled out. I assume both the drawbar and Collet threads are hardened so that will make a difference.
    If a drawbar is too long it can hit the top of the cutting tool and push it out of the collet causing stuff to bend and break. Pulling stuff out while pulling it in at the same time is not a good idea. This is especially true when power and leverage are applied.
    Bill D.

  8. #7
    Join Date
    Jun 2019
    Country
    UNITED STATES
    State/Province
    California
    Posts
    4
    Post Thanks / Like
    Likes (Given)
    1
    Likes (Received)
    0

    Default

    It gets weirder. I measured the drawbar -> toolholder thread engagement, and it came out to about 15 mm (1.25x engagement), so that's on the money. If they shorten the drawbar by that 9 mm stickout, there won't be enough engagement.

    It's BT30 toolholders and a BT30 taper in the spindle (we checked against a thread gage before installing anything). Same result using Kennametal and Maritool toolholders. Taper appears to seat correctly, thread engagement seems correct (if I tested correctly), the drive dogs are the correct length (9 mm longer and the taper wouldn't seat correctly).

    At this point, I'm wondering if there's something missing from the spindle assembly or if the drawbar was installed wrong. I talked to the dealer and asked him if they had and old crusty dude that could come out and take a look at it (the younger tech they sent earlier did a good job setting up and calibrating the machine, but he seemed stumped as well.)

    If you're curious about how I tested, I dropped a set of calipers into a top of the collet bore in an unloaded ER32 toolholder, measured the distance from that surface to the top of the threads, then popped it into the spindle and measured the distance from said surface to the tip of the drawbar. Subtract the two (~52 mm - ~37 mm) and that's how deep the drawbar is engaged, unless I'm making a mistake (which is certainly possible).

  9. #8
    Join Date
    Jul 2005
    Location
    central Illinois
    Posts
    228
    Post Thanks / Like
    Likes (Given)
    1170
    Likes (Received)
    81

    Default

    I feel your pain with that company!

    "The salesman and TRAK tech support are treating this as a low-priority issue, and suggested some "fixes" I could try. Honestly, for having spent 45 grand on this machine, I'm kinda pissed that this is an issue."

    I'm fear you have already reached the truth about them and will possibly need to accept you're on your own to figure it out and implement the fix.
    My experience having purchased a new machine from them of about equal value is that there is no, to little, service after the sale. Hope your experience is better.

    It's always made me wonder how they could ever possibly make a repeat sale to a customer. Certainly won't here!

  10. #9
    Join Date
    Jan 2007
    Location
    Flushing/Flint, Michigan
    Posts
    7,581
    Post Thanks / Like
    Likes (Given)
    377
    Likes (Received)
    6332

    Default

    BT30 holders and keys were not meant for a power drawbar.
    In order to work in such you need much taller than normal keys to grab the holder.
    They can be tapered on the ends.
    Make some double height keys if they will clear in your holder slots
    Bob
    Last edited by CarbideBob; 08-17-2019 at 01:15 AM.

  11. #10
    Join Date
    Apr 2004
    Location
    Milwaukee,WI
    Posts
    1,276
    Post Thanks / Like
    Likes (Given)
    6885
    Likes (Received)
    994

    Default

    The part that I linked to in an earlier post allows you align the tool and drive dogs before the top of the toolholder contacts the drawbar. I used it today and could not imagine being without it. For a 30 taper you would probably have to make your own and have the inside finished on a wire edm. Once you get this working you will enjoy using an open bedmill. I still use a vmc for production work.
    Maxi


Tags for this Thread

Bookmarks

Posting Permissions

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