Machining

Machining as a hobby could be regarded as an enabler for many other hobbies. Because of this, there tends to be little overall organisation to be seen. In other words, many people have the odd machine tool around the house, but few of them would belong to any sort of club specificly related to machining. For instance, plenty of car restorers, vintage or modern, would have good home workshops with a range of machine tools. The people who build miniature locomotives also tend to have good home workshops. No doubt you can think of other hobbies where the ability to cut or join metal is useful, and all of these people tend to accumulate some sort of machining facility. Woodworkers use machines too, but any information about them should be in a section called woodworking, not here.

There are also individuals who start building up a home workshop with the idea of eventually building some project, such as maybe a miniature steam locomotive, but get sidetracked into building the machine tools themselves and their accessories. The home machine shop thus may end up being an end in itself. This is potentially a perfectly satisfying hobby in itself. There are in fact at least two magazines that cater to this side of the hobby, "Home Shop Machinist" in the USA and "Model Engineers Workshop" in the United Kingdom.

Typical machines for the hobby machinist.

The basic machine is the lathe. You would hardly have any street cred as a hobby machinist if you did not have some sort of lathe. A lathe is a machine tool that generates circular sections by rotating the job around an axis and cutting it with a tool. The job may be supported between a pair of hardened points called centres, or it may be bolted to a faceplate or held in a chuck. A chuck has movable jaws that can grip the job. For a metal lathe, the tool is supported on a saddle and cross slide that permits it to be moved along and across the axis of the machine. The movements are normally calibrated so that precise cuts can be made. An additional slide called a topslide is often present, and this can be angled to permit cutting short tapers. A Screwcutting Lathe has provision for gearing the feed along the axis to the drive rotating the job. Suitable choice of ratios permits screw threads to be cut and also allows for an automatic fine feed. This allows the operator to stand and watch. With ingenuity, a lathe can perform most of the other machining tasks mentioned below, although the size of work may be limited compared to special machines. It follows that a lathe should be the first machine tool acquired and it should be as big as you can manage.

Drill press. This machine is used for drilling holes. Most hobby machinists would have either a bench mounted or floor standing power drill press. Drill bits are held in a chuck, or sometimes in a tapered hole, and are rotated at a suitable speed by an electric motor. A hand lever permits feeding the drill into the job. Clamping the job to the table or using a vice is a really good idea, especially if you like being attached to your fingers.

Milling machines.

There are two main types of mill. The vertical mill is like the drill press, but with an X-Y table that permits moving the job. End mills and slot drills (Cutters that look a little like a drill bit.) can cut slots and pockets, while other specialised cutters can cut dovetails and t-slots. Large face mills can cut flat surfaces. A combination machine called a mill-drill is quite popular with amateurs as it takes the place of the drill press and a vertical mill.

A horizontal mill has the same sort of X-Y table, but the cutters go on a horizontal arbor across the table. Cutters for this have a cross section like a circular saw but are generally wider and smaller in diameter. A number may be ganged together on the arbor to face a flat surface. Special cutters can also cut grooves or indeed any section desired, but tend to be expensive.

Shapers.

These are an older style of machine that is no longer favoured in profesional machine shops but is popular with some amateurs because the tooling for them is very cheap. The job mounts on a box shaped table in front of the machine. The height of the table can be adjusted to suit the job, and the table can traverse sideways, usually controlled by an automatic feed. A ram slides back and forth above the job, and a tool on the end of the ram cuts a flat surface on the top of the job. A small slide permits feeding the tool downwards to put on a cut. Most common use is machining flat surfaces but with ingenuity and some acccessories a wide range of work can be done.

Accessories for mills and shapers.

Desirable accesories include the following:

Vices to hold the work on the table. These are a precision vice with flat jaws to hold the job without marking it. They are much lower in profile than bench vices used for hand work.

Dividing head. These are used for machining features that repeat around a circular job repeatedly such as gear teeth or flats. The better ones are based on a worm gear and permit a very wide range of divisions to be performed.

Rotary table. A form of dividing head that has a vertical axis. Very useful on Vertical mills for setting out holes around acircle or machining partly circular shapes.

Power saws.

These include power hacksaws and bandsaws, with blades suitable for cutting metal. Very useful for cutting pieces from bar stock ready for machining or welding

Welding equipment.

Amateurs may possess a variety of welding, brazing, and soldering equipment. This includes:

Electric arc welding, which is useful for welding up structural steel elements.

Oxy acetylene welding equipment. this can perform structural welding on smalle items, but is more expensive than arc welding. On the plus side, it can also be used for cutting steel, brazing and silver soldering, and hardening high carbon steel parts.

Propane/butane torches. These cannot perform welding, but are useful for braxing, silver soldering, and hardening items.

Contributed by John Olsen




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