Screw it yourself: know-how for DIY enthusiasts

Screws hold more securely than nails and they connect practically everything. We show you how best to screw yourself and which screws you need for what.

The screw is superior to the nail: where it fails, it holds - even in ceilings. Nails cannot withstand tensile forces in the long run: If a nail is in the ceiling, it will be pulled out as soon as a load is attached to it. This problem can also appear on walls. Wall cabinets, for example, strain downwards, but also diagonally forward, and can therefore pull nails out of the wall. Screws are more trustworthy there.

To buy the right screws, you have to answer four questions: How big and heavy is what you want to fasten? Where should the whole thing be assembled? What materials do you want to couple? How nice should the whole thing look?

Screw dimensions

As a rule of thumb for the dimensions of screws, the larger the object, the longer the screw, the heavier the load, the thicker the screw. Length and shaft thickness are given as nominal dimensions in millimeters on the package, the number of pieces is noted behind.

Screw thread

The shape reveals which material the screw is suitable for. There are two types of thread: one winds steeply and with sharp edges around the screw core, the other flat and fine (metric thread). Steep, sharp-edged threads cut perfectly into the pressed wood of chipboard and sheet metal. Screws can grip better in solid wood, so the slope can be a little flatter.

Screws with a metric thread are screwed into a counter thread or fastened with a nut. They are made exactly, recognizable by the large letter M on the packaging. If the connection cannot loosen, slide a spring washer onto the thread or use a special lock nut before assembly.

Optics

Round, raised or pan head screws? Which gives the best look on which material? Plus: We present the right tool.

Often, screws not only have to serve their purpose, they also have to be beautiful. Round and oval head screws look best. You can install washers under round heads. When tightened firmly, the head does not press into the material. Flat-head screws do not protrude over the surface of the workpiece. Cap nuts on metric screws provide a nicer view, decorative caps on wood screws, wooden plates hide deeply recessed screw heads.

Screw heads (from left): countersunk, lens, round, hexagon, Allen head. Decorative caps or glued-in wooden disks hide heads.

Photo: Das Haus / Jürgen Kirchner

Screwing tool

If you only want to screw in a few screws or have to screw in hard-to-reach places, you can use hand tools. More expensive tools with hardened, magnetic blades are worthwhile. The blade should be flat at the bottom, not tapered, and its side surfaces should be almost parallel. The blade should ideally be as wide as the screw slot. When screwing large quantities, electric or cordless screwdrivers save a lot of time and energy. The interchangeable screw blades (bits) should be made of hardened steel. Electric screwdrivers find little hold on slotted screws. Phillips heads are better. The bit interlocks even more securely in Pozidriv screws: An additional hold is provided by a notch cross lying diagonally to the main cross, which means a total of eight notches.

A hexagon bit is required for metric Allen screws (Allen) - mostly used in furniture construction.

Instructions: How to screw securely

Screws sit at different depths in the wood.

Photo: Das Haus / Jürgen Kirchner

Depending on the shape of the head, screws sit at different depths in the wood: countersunk head does not protrude above the surface, half-round head, round head entirely.

Grain with the thorn.

Photo: Das Haus / Jürgen Kirchner

Grain with the thorn helps small screws into the wood. Pre-drill thicker - 2/3 of the screw thickness and screw length. Drill thicker for the shaft.

Screwdriver.

Photo: Das Haus / Jürgen Kirchner

Screwdrivers should be as wide and thick as the slot. Help for the wrist: hexagon and open-ended wrench make the last turn easier.

Screw heads (from left): countersunk, lens, round, hexagon, Allen head. Decorative caps or glued-in wooden discs hide the heads.

Photo: Das Haus / Jürgen Kirchner

The following types of screw heads are available (from left): countersunk head, pan head, round head, hexagon head, Allen head. Decorative caps or glued-in wooden discs can hide heads.

The claw head tilts the drill hole for countersunk / raised heads.

Photo: Das Haus / Jürgen Kirchner

Countersink drills create space for the head and screw shank in one operation. Krauskopf chamfers the borehole for countersunk / raised heads.

Taps help with broken heads.

Photo: Das Haus / Jürgen Kirchner

Grain the broken screws (picture at the back), drill them out, use the left-hand twist to unscrew the rest. Otherwise only taps (front) help.

Extra tip

Damaged screw heads, in which the screwdriver blades no longer grip, can be repaired with paste that hardens in the air in seconds. To do this, place a blob of the mass on the destroyed screw head. Then apply the blade of the screwdriver or bits several times with light pressure until the impression of the blade solidifies in the paste - the new replacement screw head is ready.

The tube with the stable, non-toxic and ecologically harmless paste is available in hardware stores.