Australian Facetors' Guild Limited

B & W Depth of cut meter

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  • 01 Feb 2020 11:02 AM
    Reply # 8705499 on 8697082

    Hi Gordon,

    I noticed as well that you had to find the sweet spot for the collet when putting it in the chuck. I have this collet marked so I know which way it goes in when putting the dop in the chuck. I check the runout after tightening the chuck and it will vary from zero to about 0.007mm, the distance from the dop to the quill block shaft is 140mm and the dial gauge lever 70mm. So that is a maximum runout of 0.015mm, if I put the chuck in anyway it could be triple that.

    This is my third chuck I’ve bought over the years and it’s a CR12 ER11M 150mm long shaft cut down to suit. I like them because the bearings to fix them in place are an interference fit, so don’t have to worry about wobble or movement.

    So if I do make a concave cutter I would put a 150mm long chuck in an ally block with the motor piggyback.

    Regards,

    Frank.


  • 02 Feb 2020 9:35 AM
    Reply # 8710591 on 8697082

    Thank you everyone for the replies. Thank you Paul for the photos I am going for something very similar with a gauge and the buzzer. I've got it all wired up the only issue in running into at the moment is trying to find the right spot to connect it all onto the halls faceting head. Gordon i also have a dial indicator fitted to the machine but I find all mast machines have an amount of flex in them which I'm hoping this will help with (I'm a heavy handed facetor). 

  • 03 Feb 2020 7:33 AM
    Reply # 8711588 on 8697082

    Hi Jason, 

    I read an explanation from an engineer that the bearing play needed to allow the quill to move is the reason for the reported flex.  Too much weight and you squeeze the bearing lubricant out from between the bearing and the surface it runs on. 

    I have taken to putting my hand under the quill and holding the quill with thumb and finger to even out the pressure I apply to the stone.  It allows me to rest my forearm on the edge of the deck of my machine to reduce the strain on my sholder.

    Happy faceting.

  • 03 Feb 2020 7:50 AM
    Reply # 8711619 on 8697082

    Hi Frank,

    I think I have a bit more to learn about bearings, I don't know what an interference fit is.  I am using an E11A with a 1mm to 7mm collet set as well as a 1/4 inch collet. 

    As my collet snaps into a retaining ring in the locknut, I am not sure how I canindex the collet to the collet holder.

    I have thought of putting the collet on the end of a dop, setting the angle on the faceting machine head to the taper angle and then lapping it on a 1200 lap the same way you cut a comtinuous facet.  Then wrapping some 1200 wet and dry around the collet and using it to grind the chuck and remove surface irregularities.

    Do you think this will work?

    Next time I'll get the next size up so I can hold up to 1/2 inch cutters without reducing them at the cutter end.  I can then use Polymetric cutters with 3/8th inch shafts.  I have 2 darkside polishing laps with 1/4 inch shafts, but the rest of the range have 3/8 inch shafts.

    Regards

    Gordon

  • 11 Feb 2020 7:36 AM
    Reply # 8738382 on 8697082

    Tom Herbst got the description of the Ohmmeter all wrong in his Volume 11.  It does not function as an opening and closing switch.  After the meter pointer has totally passed zero, it never returns to zero as Tom's oscilloscope sketch indicates.  Proof:  turn the lap motor off and watch the needle mimic the surface of the lap, climbing and falling but never returning to zero.

    There are many benefits that Tom also overlooked.

       

  • 13 Feb 2020 7:58 AM
    Reply # 8743672 on 8697082

    There's a thing called a carbon pile resistor, its used in speed controllers.  The harder you push in it, the less it resists current.

    I think the same effect happens with a pair of contacts, but to much less of a degree.  There is a bit of resistance when the contacts are just touching, and this gets less as more pressure is applied.  I have noticed up to an 0.4 ohm pressure variance with my Fluke multi meter's probes.

    Last modified: 14 Feb 2020 7:02 AM | Anonymous member
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