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.

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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 !

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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.
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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.

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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.

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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.

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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.

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This is how it ended up, 8 mm long, ready for threading 4-48 tpi.

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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.

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This is the result. A clean thread that fits perfectly into the dial gauge stem.

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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.


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A picture of the components. The drill is 2 mm in diameter and is the one I used in the following pictures.

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A ll 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.
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