Tools

• On this page I'll document the tools I use, both those I've bought and those I've made. The major tools in my shop are the mill and lathe. Having these allows me to make more specialized tools as needed.

Lathe

• Early on in the construction of my 'pit I started to get frustrated with the limits of my engineering capacity. I realised that if I was going to try to make instruments and other precise parts I would need a lathe. Fortunately some extra paying work came my way and I was able to afford a cheap Chinese machine. It's not super accurate like a Myford, but it's more than adequate for my purposes :-))))

• I've made some attachments and tools for the lathe. Probably the most useful is the router mount. This allowed me to achieve some milling-like operations before I purchased the mill.

• While still resisting buying a mill, I lashed out and bought a vertical slide for the lathe and some milling bits and collets to fit the spindle on the lathe. This gave me more milling capabilities.

Mill

• As my mechanical engineering capability expanded, so did my ideas and soon I outgrew the milling ability of the lathe. Nothing for it, but to lash out with the credit card again and purchase the mill. I bought one of those mini-mills hoping that it would be big enough to do what I need.

• Unfortunately,  it turned out to be too small. So I decided to sell it and buy a bigger one. I discovered that I use the mill about four times as much as the lathe, so I went the whole hog and bought a big machine. In the end though, it only cost about the equivalent of a mid-priced computer.

Gear Cutters

• I will be making a lot of instrumentation. Since it is so expensive to get gears here (like $12.00 for one small plastic gear) I decided to make my own. Also, I envisage that there will be the need for special gears that I cannot buy "off the shelf". So I decided to buy a set of gear cutters. These are specialized tools for use on the milling machine or lathe.

• Each cutter is designed to produce gears with a range of teeth. For example, the cutter shown will cut gears having between 14 and 16 teeth only. To have full capability to cut any number of teeth, takes a set of 8 cutters.
• Gear cutters are designed for a specific tooth pitch.  The pitch is referred to as the "pitch circle diameter". This is the distance across the gear measured at the line where two gears will mesh.
• I chose a PCD of 48 teeth per inch  as a good compromise size for the instruments I will make. That means that a gear that has 48 teeth will have a "pitch circle diameter" of one inch. A gear with 24 teeth will have a PCD of half of an inch. The combined radius of the gears determines where you drill the holes for the gear axles. For example, meshing a 48 tooth gear with a 24 tooth gear gives (0.5" + 0.25" = 0.75") three quarters of an inch between the centers of the gears.

Indexer

• To make gears with the mill, you need to be able to rotate the gear blank in fixed precise increments. There are commercial tools to do this called indexers. Most of them are either too expensive for my pocket, too big for my mill or too inaccurate. So I decided to make my own.
• I wanted to have as much flexibility in handling the materials as possible, so I decided to have a spindle with a standard taper inside that could take collet chucks as well as having a faceplate which could take parts bolted to the front or a small 4 jaw chuck. I started with a thing called a "drill extension". It had a 3MT socket at one end and a 2MT tang at the other. I needed the socket, but not the tang. So I cut off the tang and threaded the end to take a bearing piece. The other end I threaded to take a faceplate. I made and threaded the faceplate and bearing end to suit the spindle. The middle pic shows a collet chuck in the spindle socket.

• Since the frame would be made from aluminium, I couldn't let the spindle rotate in just the frame. So next I made a set of steel bearings to carry the spindle. The front bearing also has a locking collar so that the spindle position doesn't change while machining.

• Then I made the frame to carry the spindle. The alignment of the bearings was critical, so a lot of care was needed when boring the holes in the frame ends. The right hand pic shows the 4 jaw chuck mounted. With the chuck mounted and the spindle in just the frame, the assembly looks like a mechanical ant. With a bit of imagination, the frame looks like the body and the chuck looks like the head with massive jaws and even eyes. So I decided to call the indexer "The Bull-Ant".

• To make setup on the mill easier, I decided to mount the whole indexer on a base. Then I could bolt the base to the mill table and if the base was straight, the whole thing would be straight. Eventually there will be a tailstock with a centre to hold the blanks in position. This will also be bolted to the base.

• To give the precise positions for gear teeth, what would be better than to use the teeth of another gear. So I made the spindle to take the gears from my lathe as the indexing devices. There will be a spring loaded pin mounted in a block that will wedge in between the gear teeth. This pin and block will be mounted on the plate that clamps to the rear bearing.

• A gear from the lathe mounts to the rear of the spindle. Later, I will make a second shaft that will mount to the pin plate that will carry more gears. Then I can use compound gearing to set oddball ratios if needed.

• This is the indexing pin and it's mounting block. The end that engages with the gear teeth has been shaped to a forked end. This allows indexing in between teeth or on a tooth. In essence it allows me to index by a whole tooth or half a tooth. This is useful for odd numbers. For example, I have an 87 tooth gear and indexing by 1.5 teeth give me 58 positions for one rotation.

• Here's the indexing pin mounted and in use; in Vertical mode and Horizontal mode.

• With the addition of the tailstock, the indexer is nearly finished. It still needs some holes in the base to allow it to be bolted to the XY table of the milling machine.

Lens Clamp

• Making the lenses for various gauges posed a problem. How to hold a piece of acrylic securely enough to machine it round, but without drilling any holes in it. For some time I've had an idea festering away in the back of my head, for a clamping mechanism, that would hold the blank securely, yet let it rotate with the lathe spindle. The idea was a faceplate mounted on the spindle to hold and drive the blank and a pressure pad mounted to the live centre to clamp the blank, yet let it rotate. I finally got around to it.

• The first pic shows a piece of acrylic clamped in the lathe. The second pic shows the parts of the clamp with a test lens. The third pic shows that the clamp didn't scratch the lens during the machining. The pressure pad has a bit of gasket paper glued to the pressure face. This allows for any misalignment between the pressure plate and the faceplate and gives a bit of grip. The faceplate is 48mm diameter, so it will work for 2" or 3" lenses. The clamp works extremely well, and the best part is that the edges of the lens come out  smooth and even.