Australian Facetors' Guild Limited

Laps sticking to master plate

  • 13 Mar 2019 4:44 PM
    Message # 7216314

    My 6” diamond faceting discs are on aluminium backing plates. Problem is, after a session of using one, they always seem to get small amounts of water (capillary?) seeping in between the backing plate and the machine master plate. And they can be a pain to get off. The water seems to act like a vacuum or glue. I’ve tried using a rubber washer when screwing onto the master plate, but it is only a so-so fix. I’m wondering if I should cut a few shallow crisscrossed lines across the bottom of the backing plates to act as relief channels.

    Anyone else had similar issues and found a solution? Or any tips?

  • 14 Mar 2019 7:58 AM
    Reply # 7217824 on 7216314

    Using your finger or a cotton bud apply baby oil or Vaseline to the underside edge of the lap in a strip about 5 - 10 mm wide.  Do the same around the central hole.  Make sure that the master lap and the underside of the lap are dry before you do this procedure.  The lap will still have resistance when you try to remove it however not as bad as it is when wet.  Sharpen the end of a wooden spatula (ice cream stick) to a chisel point and use it to break the seal between the lap and the master lap.

    Bruce H.

    Port Augusta SA

  • 14 Mar 2019 5:54 PM
    Reply # 7218312 on 7216314


    Has anyone tried using a disk of that silicon baking paper between the lap and master lap.

    I expect it would be uniform enough not to cause the lap to be unlevel.

    Has anyone tried it?

    I initially tried a disk of BBQ non stick mat for frying hamburgers thinking it would help get the topper laps off my magnetic master lap, but since gave up in favour of sliding the topper off the lap sideways using the heel of my hand.



  • 14 Mar 2019 6:23 PM
    Reply # 7218316 on 7216314
    Anonymous member (Administrator)

    The problem would be solved if machine manufacturers made the master  about 1/2" smaller diameter than the 6" laps. Trouble is the lap makers would probably reduce the lap diameter and you would be back to square one.

  • 17 Mar 2019 2:04 PM
    Reply # 7228053 on 7216314

    If both surfaces are dry, then they’re going to stay dry. So, sounds to me like water is still getting through the central locking nut, or your letting water drip while the lap is stationary. All assuming that the master lap is smaller than 6”.


    I don’t put anything between the master lap and cutting laps, which are all glue on bonded laps. The type that have diamond bonded to a thin disk, which in turn is glued to an aluminium backing disk. Some of them have a brass shim sandwiched between them and the master lap where I have been able to detect runout with the dial gauge.

    Putting the lap on the same way and shim in the same spot keeps them running true.


  • 18 Mar 2019 7:41 AM
    Reply # 7228782 on 7216314

    Some good tips and advice here which I have been trying out. Thank you for assisting. The thin border of oil seemed to work quite well for me yesterday. And I saw a comment about leaving the drip on with the lap stationary and had a d’oh moment - guilty. Might need to assign a few remaining brain cells to the common sense department.

    T Spinks

  • 01 Apr 2019 3:36 PM
    Reply # 7254244 on 7216314

    Two suggestions: If the lap sticks spray some WD40 around the centre and the outside. Otherwise cut a "gasket" out of a piece of computer paper - this is an old trick which was formerly used back in the day when a lot of people only only had one cutting lap, usually with 260 grit rolled into one side and 1200 on the other side.

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