Barrel ID Measuring tool

[Tmuir]

It's time to get back to working on my Fusee clock and finish the new barrel for it.

Although I could manage without making this tool I decided it was worth making to ensure I get the endshake correct.

I wanted to measure the distance between the bushes inside the clock barrel and obviously you cant use a vernier for that.

That's where this tool comes in.

Its a pretty simple tool. The threaded rod is a 6BA steel threaded rod I had lying around and I turned up 2 brass ends. The one on the left is only threaded for about 10mm and the rod is screwed and Loctited into it. The one on the right is threaded for the first 10mm and then just clearance drilled the rest of the way. I did this as my taps are not long enough to tap the whole length.

The shoulders of the brass ends are 7.5mm diameter with the narrow parts 5.5mm diameter. The idea is this can be used on any barrel that the pivots are larger than 7.5mm.

Before I get onto how to use it I will quickly show how I tap small threads like this.

The picture below shows my lathe fitted with a drill chuck in the tail stock and held in the drill chuck is a steel rod that I drilled and reamed to give it a smooth bore.

I then turned up the tap holder with the shank to the size its a nice smooth fit into the bore. The end of the tap holder is drilled to be a good fit on the tap shank size, knurled to give you some grip and then a grub screw hole is cross drilled and tapped and a grub screw fitted, so when you slide in the tap the grub screw is tightened up on one of the flats of the square on the end of the tap.

The drill chuck and reamed tube hold the tap in line for tapping and as you screw the tap in by hand it slides in the tube so no stress is put onto the new threads being cut. You can obviously also use this in a drill press.

A closer shot of two tap holders and the sleeve, they are each made for different size taps

Measuring tool in use.

The shoulder of the left side is sat against the shoulder of the bush inside the barrel and the other brass end is gently wound out until it is touching the shoulder of the other bush, then the 6BA nut is done up against it to stop it slipping, you then remove it from the barrel and use your verniers to measure the gap between the shoulders on the measuring tool. I can now ensure that my new barrel will have the same amount of endshake as the old barrel, yes I could of worked it out without making this tool, but its always fun making new tools.

 

[oldhippy]

The fun of having your own lathe is making tools to help you with the work you need to undertake.