Machining metal: How it's done

Knowledge about metalworking:

Around 10,000 years ago, people in the Near East began to work metal. The first and, for a long time, only metal that humans were able to work with was copper. The art of metalworking was refined over the following millennia and more and more metals were discovered, developed and used over the course of time.

Today, a wide variety of metals, from aluminium to zinc, can be found in almost every everyday object, every machine and every household appliance. Different machining methods are sometimes used for different metals in order to achieve optimum machining results. Nevertheless, metalworking is no longer an art. Whether in the trade, in the hobby room or in industry. Metalworking is part of everyday life. This is also reflected in the many different professions related to metalworking. In the following guide, we answer some of the most frequently asked questions about metalworking.

Table of contents Machining metal:

• What is the difference between a hacksaw and a wood saw?

• Can metal be glued?

• What is the difference between soldering and welding when working with metal?

• What do HSS and HM/VHM mean for drill bits used to machine metal?

• Which sandpaper for working on metal?

• Can I cut metal with a hand-held circular saw?

• What is an edge router used for?

What is the difference between a hacksaw and a wood saw?
 

A hacksaw and a wood saw differ in various ways. A metal saw is usually more sturdily constructed than a wood saw. Metal saws must be able to withstand higher forces when sawing than a saw used to cut wood. You will not find a saw frame made entirely of wood, as is still common for branch or tree saws, for example.

As a rule, a metal saw has considerably more teeth per inch (25.4 mm) - this value is often given as TPI (Teeth Per Inch). A metal saw blade with an average of approx. 24 to 32 teeth per inch is significantly finer than a wooden saw blade with approx. 8 to 12 teeth per inch. In addition, the saw tooth geometries (e.g. cutting, clearance or rake angles) are very different for metal saws and wood saws. There are special saw blades for practically every metal that enable optimum sawing results.

Can metal be glued?
 

Today, there are various high-performance adhesives that can be used to bond metal workpieces together permanently and reliably. More and more metal parts are being bonded instead of riveted, welded or screwed, and not just in industry, for example in automotive engineering. As adhesive joints are now as resilient as other mechanical joints, the significantly lower weight of the adhesive seams plays an increasingly important role when bonding metal parts.

For some time now, high-performance adhesives for bonding metal have also been available for DIY enthusiasts. For example, epoxy or polyurethane adhesives. The adhesives are very easy to use and do not require any special skills. The glued seams are at least as robust and durable as a screw or rivet joint when working with metal in the hobby workshop. It is important that you follow the adhesive manufacturer's specifications and instructions when bonding metal. It is also advisable to wear suitable protective clothing with gloves, safety goggles and, if necessary, respiratory protection.

What is the difference between soldering and welding when working with metal?
 

Soldering and welding are two processes that can be used to permanently join metal workpieces together. One difference lies in the working temperature. The working temperature for welding is significantly higher than for soldering. The most important difference is that when welding, the material of the workpieces to be joined is heated to such an extent that it melts at the joint. The molten metal then flows into each other, creating a joint.

Soldering, on the other hand, uses a so-called solder, which is also a metal. The seams of the workpieces are heated to a certain temperature so that the solder melts and fills the seam. When the solder cools, the two workpieces are joined together. Soldering is often used to join non-ferrous metals such as copper or brass. Workpieces made of steel and aluminium, on the other hand, are usually welded.

What do HSS and HM/VHM mean for drill bits for machining metal?
 

HSS and HM/VHM are two abbreviations used to designate the material from which drill bits for metalworking are made. HSS is the abbreviation for "High Speed Steel". The literal translation of the English term is "high-speed steel". However, the term high-speed steel is more commonly used. In any case, this is a high-alloyed so-called tool steel. This material was specially developed for use in cutting tools. HSS is relatively hard and retains this hardness up to temperatures of around 600 degrees. With HSS drills, a cutting speed up to four times higher than drills made from normal tool steel is possible.

HM and VHM are abbreviations for "carbide" and "solid carbide". The term carbide is used for drills in which, for example, only the front part is made of carbide. In a solid carbide drill bit, the entire drill bit from the tip to the shank is made of carbide. Compared to normal tool steels and also compared to HSS, carbide enables a higher feed rate and a higher cutting speed when drilling. Carbide and solid carbide drills are more dimensionally stable, less sensitive to heat and have a significantly longer service life.

Tip: Machining aluminium
 

Aluminium is a soft metal that tends to "smear " when sawing and drilling. Smearing means that the material settles on the tool and further machining becomes almost impossible. When working on aluminium, a suitable cutting agent/cooling lubricant should therefore always be used to prevent the material from "smearing" and sticking.

Which sandpaper to use when working on metal?
 

The choice of the right sandpaper for metalworking depends on the desired end result. The grit size and whether the sandpaper is suitable for dry or wet sanding are important when selecting the right sandpaper. Wet sanding paper is always recommended for fine sanding results .

Sanding paper is available in handy A4-sized sheets or on a roll. For machines, there are pre-assembled discs that you can use for random orbital sanders or orbital sanders.

The grit size of sandpaper for metalworking starts at around 60. This is the coarsest grit size. You can quickly remove paint or rust from metal parts with 60 grit sandpaper. The higher the grit size, the finer the sandpaper. To achieve a very smooth, fine surface, you will generally need 3 to 4 different grit sizes with increasing fineness. Sandpaper with a grit size of 7,000 has the highest fineness. You can polish metal surfaces with this fine grit.

Can I work on metal with a hand-held circular saw?
 

You can also work with metal using a powerful hand-held circular saw. However, a normal HSS or carbide saw blade is not used for this. A so-called cutting disc is used to cut metal with a hand-held circular saw. Saw blades with very fine carbide teeth can also be used for certain metals such as aluminium. Despite a good machine, metalworking with a hand-held circular saw requires a lot of strength and experience. It is better to choose a different saw for this work , such as a jigsaw, a band saw if possible or a chop saw .

It should also be noted that certain metals, such as some aluminium alloys, tend to stick to the teeth of a circular saw blade when working with metal, meaning that the tool stops cutting relatively quickly. When working with an electric hand-held circular saw, it is of course not possible to lubricate the saw blade with a cooling lubricant. A different saw should therefore be selected, at least when working on aluminium.

What is an edge milling machine used for?
 

An edge milling machine is used for two tasks when processing metal. With such a machine, the edges of metal workpieces can be deburred in just a few simple steps. Burrs always occur when the surfaces have been machined or the workpieces have been sawn to a certain size. In the past, deburring was and still is often carried out with a file. However, an edge trimming machine performs this work much faster and more precisely.

The second purpose of an edge trimming machine is to mill a dimensionally accurate phase on the workpiece edges. Workpieces processed in this way are safer for the craftsman to handle during further processing and bevelled edges simply look better.

Tips for DIY enthusiasts when working with metal: