CABLE “BIRDCAGE” TOOL

If you refer back to the blog post of 14th August 2013 entitled “Under the Wire” you’ll find a piece on making up control cables.

In this I used a crude method of splaying out the end of the inner wire, basic but it does work.

I was recently shown a special tool for doing this which made a better job of doing this. When I went “on line” to find this tool I discovered that it had a ridiculously high price for what it was, just over £123.

Having had a good look at the tool I knew that I could make one for myself, so I got a length of 8mm by 25mm “bright steel” bar.

I cut two 100mm lengths from this, I put them one on top of the other in the drill vice on my post drill, squared them up and put two 5mm holes through them, on the centre line, one each about 20mm from either end. I then opened out the holes on one piece to 6mm clearance and tapped those in other bar to a 6mm thread.

I could then bolt the two bars tight together, hold them in the bench-vice and draw-file one long face to ensure that both bars were dead level.

I took the bars apart and then re-assembled them with a piece of card, about 0.16thou thick, between them, put them back into the drill press vice. I next put a pop-mark, spot-on the centre divide and in the middle of length of the bars, and then another two, one each about 25mm either side of that.

Next step was to drill a 6.1mm hole, 10mm, deep at each pop-mark.

As there are three different cable sizes to accommodate I then extended these through the bar, one with a 1.5mm drill, one with a 2mm drill and one with a 2.5mm drill.

Now comes the crafty bit, A standard drill has a 118° point so each of these holes now had a shallow conical join where the drill size changed. I wanted a deeper cone here.

You can get what is known as a “spotting drill”. This is intended for marking out work, not for hole drilling, and it has a 90° point so I took a 6mm spotting drill and deepened each hole by about 2mm.

That was the main body of the tool made, I dismantled it and discarded what was left of the card.

I now had to make three punches, one for each size of cable.

I cut three lengths of 6mm round steel bar, each about 5 inches long, fired up the lathe and squared off the ends.

I then used the spotting drill and sunk a 90° socket in the end of each, these were to form the cable end into a double conical “birdcage”.

As the diameter of the relevant cage for each cable diameter was different I now needed to form the punch ends appropriately, a diameter of double that of the cable itself was about right. This meant that to achieve this I would need the open end of the conical punch to be that size and I achieved this by cutting a 90° taper onto the end of each punch until its socket was of the required diameter.

To form a cable end I now have the tool body assembled loose, put the cable end into the appropriate bore and nip up the bolts. Because the bore had been made with the card between the bars the bore is undersize and the cable is firmly held in place.

The appropriate punch is now inserted into the larger top drilling and pushed home. The cable can now be slid further up in its bore until it bottoms in the punch socket and it then further in by its own diameter.

The tool is then bolted tight shut and placed in a bench-vice to hold it and the end of the punch struck with a hammer. This forms the end of the cable into the required “birdcage” which will lock it in place when the nipple is soldered in place.

I could have made this up using angle iron to be easier to hold it in the vice but the only “bright steel” angle I could get was either way too big or if in a convenient size only had a 3mm thickness so I had to use the plain “bright” bar.

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