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  1. #1
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,444

    Thumbs up Dial Gauge Roller Tip !

    Hi Guys,

    A little while ago I made an Elephants foot tip to fit my dial gauges ! Having seen a picture of a Starret Roller Tip, I decided to have a go at making one.

    Roller tip.jpg
    The picture is the one that I found on the Starret web site. The roller is 5 mm in diameter and 3 mm thick.
    Now as it happens I have a new Japanese precision roller bearing that almost meets the same dimensions as the Starret one.
    Mine is 3 mm thick and 4 mm in diameter with a 2 mm through hole. So I thought, I can use that !

    Bearing.jpg Bearing-2.jpg
    At this point its difficult to judge the size of this from the pictures.

    I started with an aluminium shaft that I salvaged from an old potentiometer.
    13-01-2019-002.JPG 13-01-2019-001.JPG
    The shaft is 1/4" inch in diameter and just short of 2 inches in length. The knurled bit fitted into a paxolin disc with the wiper contacts fastened to it. The flat is where the control knob was pushed on. The little spigot on the end simply supported the shaft at the far end.

    13-01-2019-005.JPG 13-01-2019-004.JPG 13-01-2019-003.JPG
    Using a 1/4" ER32 collet I turned off the spigot at one end and then drilled a 3 mm hole 4 mm deep into the end. I also cross drilled a 1.1 mm hole and ran a M1.4 x 0.3 tap through, with the initial intention of using a screw through to secure the bearing. An Idea which I later decided against. More about that later.

    13-01-2019-007.JPG 13-01-2019-006.JPG 13-01-2019-008.JPG
    Since I had some screws of the right size I toyed with the idea of trapping the bearing between the sides with a screw from each side.
    It was then that I realised that any tension from the screws would tend to push the sides away from each other. So that Idea got dismissed. However I've included the pictures because they illustrate the idea.

    13-01-2019-011.JPG 13-01-2019-012.JPG
    After turning the shaft round in the collet I parted off the excess length. I then turned it down to 2.85 mm for the length of thread I needed to fit into the dial gauge stem.

    13-01-2019-014.JPG
    This is how it ended up, 8 mm long, ready for threading 4-48 tpi.

    13-01-2019-013.JPG 13-01-2019-015.JPG
    In these two pictures I'm setting the threading tool bit to the centre line hight of the work piece and using the face of the collet to ensure that the threading tool bit is dead square to the work piece. Since the thread depth is quite shallow I cut the thread in four passes with the lathe running in reverse at about 600 rpm. Since the cutter is moving away from the chuck this doesn't cause the problem of the cutting tool hitting the chuck, which it would if I was cutting in the conventional direction. I also used diesel fuel as a cutting lubricant.

    13-01-2019-017.JPG 13-01-2019-018.JPG 13-01-2019-016.JPG
    This is the result. A clean thread that fits perfectly into the dial gauge stem.

    18-01-2019-002.JPG 18-01-2019-001.JPG 18-01-2019-003.JPG
    In these pictures I'm setting the work piece in the mill vice prior to running a 3 mm diameter slot drill across between the sides. I used an engineers square and a 1.5 mm drill to make sure that the slot would be parallel to the sides. The slot was set for 4 mm deep. Actually it ended up a couple of tenths more, not that it mattered.

    After I had milled the slot I drilled the holes in the sides out to 2 mm. Having decided that a pair of screws or a threaded pin to secure the bearing was a bad idea and that using an aluminium pin was a better solution to securing the bearing.


    18-01-2019-009.JPG
    A picture of the components. The drill is 2 mm in diameter and is the one I used in the following pictures.

    18-01-2019-006.JPG 18-01-2019-005.JPG 18-01-2019-004.JPG 18-01-2019-008.JPG
    All that is needed to complete this little project is an aluminium pin and a 4-48 nut which I'm going to have to make since I can't find one in any of my boxes of nuts, bolts and screws.

    Its taken around six hours to make this dinky little thing and I've absolutely no idea what the cost of the bearing would be. There are no markings of any description on it and I didn't keep the packet it came in.

    Thanks Guys.
    Best Regards:
    Baron J.

  2. #2
    Join Date
    Oct 2015
    Location
    melbourne
    Posts
    473

    Default

    Hard disk drives (ex computer) abound with little bearings and pins that could be salvaged for something like this.

    No nuts though...

    Russ

  3. #3
    Join Date
    Oct 2011
    Location
    Norwood-ish, Adelaide
    Age
    59
    Posts
    6,542

    Default

    We had one of those at work and it was a little disappointing as we wanted to measure variations in a cylinder bore (the indicator was mounted on a sled and we had a web cam to show the readings as it was pushed/ pulled along). We found that the variation in the roller meant that the 'background' movement produced too much noise for our application.

    It may be fine for what you want to do (and using a bearing may improve things) but I would suggest putting it on a really sensitive indicator and running it across a surface plate to see what your error is on a known flat surface. Certainly for us measuring in 1/10ths it did not work. We were trying to avoid scratching the bore but perhaps a ruby tip may have been better.

    Michael

  4. #4
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,444

    Default

    Quote Originally Posted by russ57 View Post
    Hard disk drives (ex computer) abound with little bearings and pins that could be salvaged for something like this.

    No nuts though...

    Russ
    Hi Russ,

    Yes I agree ! I've salvaged many useful bits from them. Some do have coarse American threaded screws in them but most are metric. Lots of nice Torx head screws.

    The tiny bearing that I used came in a box of bits and pieces, and was packaged in a vacuum sealed bag. There was some writing on it but I just ripped it out of the bag and threw it away.
    Best Regards:
    Baron J.

  5. #5
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,444

    Default

    Hi Michael,

    Thank you for your interesting notes.

    Part of the idea for making this roller tip was having made the Elephants foot, which is basically a static device that rubs on the work piece, was to see if using a roller would be any better against a slowly rotating surface.

    However I will do a test against a surface plate and see what effect I get. Hopefully because it is a bearing it should be less noisy. My best indicator is 0.0001 and the digital Mitoyo gauge that I picked up a while back only goes to 0.0005 plus the tip is the wrong thread ! It seems that it is a metric threaded one. I've also found that the stem is too thick to fit my magnetic stand as well. Another round toit
    Best Regards:
    Baron J.

  6. #6
    Join Date
    Nov 2010
    Location
    Gippsland Victoria
    Posts
    733

    Default

    Hey BaronJ,

    I salute your patience in working with little fiddly things. Its encouraging to know that if I have to I might be able to cut tiny threads on my lathe.

    Often wondered about how to prevent dropping and losing stuff whilst working with tiny things, I scattered a few magnets around the benchtop and nailed a lip onto the edge of the bench to prevent stuff from being dropped and rolling away and getting lost on the floor somewhere.

    Bill

  7. #7
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,444

    Default

    Hi Bill,

    Thank you for your post. Having a Myford lathe with a quick change gearbox helps considerably. 4-48 is selectable directly, and a single gear change allows metric threads to be cut.

    I seem to be in a similar position the workshop gremlins keep hiding things ! Often to be found days or weeks later in the same place as they were left.
    I use a piece of old towel on the bench to stop things rolling off ! I've now started to pin the top edge to the bench because I've dragged it off a couple of times when moving away.
    Best Regards:
    Baron J.

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