Deckel FP3 "Y" Axis, backlash adjustment?
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  1. #1
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    Default Deckel FP3 "Y" Axis, backlash adjustment?

    G'Day Fella's,

    I have a an older Grey coloured FP3, and the "Y" axis has a bit of backlash in it.
    This is 0.064" or about 1.6mm, on the adjustment/safety wheel dial.
    Is there any external method of adjusting/reducing this amount of backlash?

    dscn1840.jpgTTACH=CONFIG]237494[/ATTACH]

    I've looked thru my machine manual, and online, but without success.

    Any advise on this, would be very much appreciated

    Regards
    Homer

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    Backlash can have various causes :


    • Worn out screw and/or nut
    • Loosened leadscrew
    • Loosened nut thrust bearings
    • Play in the bevel gears set


    First thing I'd check is if backlash is consistent over the whole travel of the ram ? If so, your leadscrew is most likely not the problem because most of the time, the ends of the screw don't show as much wear as the central portion.
    If not, that may be the sign that you're in for a screw replacement... 1,6mm is a lot of backlash for a screw that has a 2,5mm pitch !

    Then I'd take the bellow and the rear cover of the y axis off, so as to have a better sight at what's going on when I crank the handwheel.

    Make shure the leadscrew is tight on its bracket, and the bracket is tight on the ram.

    Then try to determine if there's no abnormal axial play in the nut, wich is held in place axially between two needle thrust bearings.
    The play is set via three set screws a kind of washer that may be loose.

    Check the mesh of the bevel gears. You never know.

    Once you've checked all the above, you should have a pretty good idea about what's the problem.
    But indeed, "external" may not be sufficient to cure it.

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    Thank You TNB, for that comprehensive list of possible problems and solutions, Very Much Appreciated!

    I'll have a look tomorrow, and see what I can see.
    Once I have worked out the cause of this and resolved it, I'll try to remember, and report back for others benefit.

    Regards
    Homer

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    G'Day Fella's,

    As per your suggestions TNB, I got into this job, earlier today.
    It didn't take me long to track down the culprit.
    There is a 4.75mm Dia x 30mm long drive/shear pin, on the rear of the Y Axis lead screw, and this had sheared, on both sides.

    Here are some images of the rear area of the mill, and the culprit and it's replacement.
    dscn3008.jpg
    dscn3010.jpg
    dscn3012.jpg
    Two of the three pieces, and the new replacemenmt shear pin.
    dscn3013.jpg

    Not sure why the shear pin is 4.75mm Dia and not 5mm, I machined down a piece of 5mm round Silver Steel (pictured), and replace the broken pin with this.

    I now have just 0.0105" of backlash on the Y axis (0.007" on the X Axis, and 0.0015" on the Z Axis).

    A Big THANK YOU to TNB and Practical Machinist.com,for your help in resolving this issue/problem, Very Much Appreciated!

    Regards
    Homer
    Last edited by HomerOz; 09-10-2018 at 05:00 AM.

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    I would be wary of making a shear pin out of Silver Steel You want the pin to shear before a tooth breaks off if you have a jam up.

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    That’s not a shear pin, it is a metric taper pin, with a 1:50 taper. You should use a taper reamer to clean up the hole before fitting a new one. Maybe broken in a Y axis crash.

    You can see some photos from a similar FP2 in this post and in the thread that contains it: FP2 shear pin and Y-axis crash

    (Please note that in the thread above, the term "shear pin" refers to the shear pin (located in the base of the machine) which protects the feed gears. It does NOT refer to the taper pin in question.)

    PS: the crash may have bent the round flange over the end of the lead screw, or the bracket that it mounts on, or the lead screw itself. If so, when you replace the taper pin and remove the "slop" you may find that there is too much friction between the lead screw and the nut. So when you have the lead screw off, put it in a lathe or between centers and check that it is straight. If not, identify where it is bent and straighten it. Then, after you reattach the round flange with a new taper pin, put the assembly back into the lathe and true the mating surface of the flange. Finally, check that the bracket where the flange attaches is true and not bent/deformed. The fitting between the relevant parts (screw/nut/ways) is close enough that even small errors can cause problems with the "feel" of the axis.
    Last edited by ballen; 09-10-2018 at 07:33 AM.

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    Every time you have a problem like this look if the Y-feed is disengaging propperly
    These kind of things and worse (much worse) happen when the dogs to disengage the Y-feed are not working properly When the Y feed is in rapids then there is nothing to stop that mass exept something that can break
    Fixed a few
    Angle piece bent
    Thrustbearings in pieces
    Nut jammed up
    Spindle bent
    Your is a easy fix then



    Peter

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    G'Day Fella's,

    Thank You Peter F, Ballen and Peter from Holland, for your great advice.
    I will check the things you have suggested, address any issues and report back asap.

    Regards
    Homer

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    FYI, I measured the broken shear pin parts, and it is a parallel pin and not a taper pin.

    When I can find some soft, bright mild steel bar, I'll make a replacement shear pin from that.

    Regards
    Homer

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    Quote Originally Posted by HomerOz View Post
    FYI, I measured the broken shear pin parts, and it is a parallel pin and not a taper pin.

    Regards
    Homer
    Someone has monkeyed with that machine...guaranteed it should be a taper pin..that is how Deckel made a tight, strong, no play joint.
    Betting the hole is not straight....unless someone reworked it.
    Ream the cross hole to clean up with the appropriate tapered reamer ....Either inch or metric (the taper rates are slightly different)
    Once the hole is true and clean with no hollows or low spots over its total length ,simply buy a commercially made taper pin (metric or inch to match your reamer) of the correct size to suit the corrected hole.

    This is not a shear pin...its not intended to fail to prevent damage...Its there to stay...tight and strong. The power feed is fitted with a shear pin, put this is not it.
    If that pin has failed its likely that you have bigger issues than just the pin.
    Cheers Ross

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    Quote Originally Posted by HomerOz View Post
    FYI, I measured the broken shear pin parts, and it is a parallel pin and not a taper pin.
    What Ross wrote above is correct. That should be a taper pin, and the fact that it's a parallel pin may explain why it's broken and also why it came loose.

    Do you have a parts manual for your machine? This is very useful, because (for example) it will indicate the pin type and dimensions. If not, ask here and someone may send you a scan or point you to one.

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    G'Day Fella's,

    Thank You for your comments and advice on this subject, I've taken that on board.
    I have Taper Drills, Taper Reamers and also, Taper Pins (Imperial or Metric???) to suit, so when I get a chance to do this, I will.

    Regards
    Homer


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