WORKSHOP – USES FOR A ROTARY TABLE
Rich describes how a home-made addition to his milling machine came into its own during his latest loco construction project.
Back in the January 2020 edition of EIM I described how I made an 11-inch rotary table for my milling machine, using a car brake disc. Recently I had cause to use the disc for a model engineering job which I thought it might be interesting for fellow readers to describe.
I needed to make the smokebox for my current loco build, ‘Chub’, a 5-inch gauge 0-4-0 (marketed by Kennions – www.kennions.co.uk/chub – Ed). The front and rear plates are available as castings but I wanted to make a couple of modifications so fabrication was the way to go.
When it came to assembling Conway, my first loco build, I had great difficulty getting my hands through the smokebox door to connect up the various pipes and such like. On this loco I wanted to make the opening as large as possible so I decided a removable front plate would be better and give greater access.
For the front plate I rolled a bit of ¼-inch square brass into a 5-inch diameter circle using my home rollers (Photo 1). The lower part of the front plate is made from ¼-inch thick brass and needed to be machined to match the radius of the rolled brass ring.
Rotary revelation
This is where the rotary table comes into its own. With the new DTI alignment tool it took only five minutes to set up and be ready for use. A paper print-out was spray-glued onto a ¼-inch thick brass bar which had three holes drilled in it (Photo 2). This was aligned on the table at the required radius and screwed down with large self-tapping screws.
With a ⅛-inch carbide cutter in a collet it took only minutes to cut through taking cuts of about 1mm (40 thou) at a time (Photo 3).
The ring was then silver soldered onto the lower plate and cleaned up (Photo 4).
I now needed a 5-inch diameter brass plate 1/8-inch thick with a 3¼-inch hole in it. A brass plate was centred and screwed to the table (Photo 5).
Using the same 1/8-inch cutter the central 3¼-inch hole was cut out (Photo 6), followed by cutting the outside diameter to 5 inches (Photo 7), the whole operation taking less than 15 minutes.
Photo 8 shows the plate placed on top of the ring. The plan is to join the two of them together using a ring of bolts.
I have put three short videos on Youtube of the cuts being made – you can find them at; https://youtu.be/t9ou3fca8va https://youtu.be/1g_cqdw_z4g https://youtu.be/pxxl2hkewo4
I hope readers will find my efforts of interest!