What is the best drill bit for blind holes?

What makes a wood drill bit so different from a masonry bit? And why is it so important to use the right type of wall anchors? We’ve put together some tips on choosing the best drill bits and anchors for any task – so you can avoid breaking any more drills and can make sure your shelves stay firmly on the wall.

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4. What is the right kind of wall anchor for my project?

1.1.5 The right drill bit for plastic and various other materials (e.g. wood and metal)

1. Choosing the right drill bit

The type of drill you need depends on several factors: the type of material you’re drilling, the type of hole you want to make, and the size of the hole (depth and diameter).

 

1.1 What type of material are you drilling?

Generally speaking, drills can be divided up into metal drills, wood drills, masonry/concrete drills and multi-purpose ones. Most drill bits have a spiral shape – which helps to remove the drilled material from the hole.

The right drill bits for metal/aluminium, stone/concrete, wood and plastic

1.1.1 The right drill bit for metal or aluminium

Whether you’re drilling iron, steel, copper, brass or aluminium, it’s best to use a drill bit designed especially for metal. These are usually made from high-speed steel (HSS) and are cone-shaped at the top.

To prevent the tip of the drill from wearing out (drilling at too high a speed or with too much pressure may cause it to turn blue), try using drilling fluid or cutting oil. You could also remove the drill from the hole at regular intervals, to allow it to cool down slightly.

1.1.2 The right drill bit for wood

Soft or hardwood, chipboard, plywood or MDF panels – for all these types of wood, you’re best off using a wood twist drill bit. This has a centring point that enables you to position the drill precisely. Furthermore, tapered drill bits help to avoid ripping up the wood.

1.1.3 The right drill bit for stone or concrete

A masonry or concrete drill bit is the preferred option for drilling very hard materials like concrete, natural stone or granite. It has a carbide tip and is usually made from tool/carbon steel.

1.1.4 The right drill bit for tiles

For drilling soft to medium-density tiles, you can use a special tile drill bit with a diamond-ground carbide tip. To prevent the drill from slipping off the surface, try sticking some tape to the tiles first and then drilling the hole. Some advice: start on a low speed setting and then gradually increase it as the drill bores deeper into the material. To avoid cracking your tiles, it’s important to apply the right amount of pressure. Apply moderate pressure to begin drilling the hole, then light to very light pressure as you proceed.

1.1.5 The right drill bit for plastic and various other materials (e.g. wood and metal)

MultiConstruction drill bits can be used to drill into plastic and a range of other materials – making them ideal for drilling cabinet doors, for example, which consist not only of wood, but may also feature metal elements/fixtures. They are suitable for use on all materials that you’re likely to work on in the home, including multi-layer materials, bricks, tiles and aluminium. However, where possible, it’s always better to use the special drill bit for a specific type of material than the MultiConstruction bit – because these are developed especially for the material in question.

1.2 Choosing the right-sized drill bit

The diameter of the drill bit you choose will depend on how big a hole you want to drill. Most drill bits nowadays have diameters of between 1 mm and 20 mm.

You can also determine the size of the drill bit based on the screws you want to use. The diameter of the hole you drill should be slightly smaller than the diameter of the screw. So, for example, if you’re using a 3.5 mm screw, use a drill bit with a diameter of 3 mm.

If you're using wall anchors as well as screws, the drill bit and anchors should have the same diameter.

The diameter of the drill bit and the material you want to use it on will also determine the drill speed.

Tip

INSIDER TIP: HOW TO CHOOSE THE RIGHT DRILL SPEED

• Small drill bit diameter: high speed
• Large drill bit diameter: low speed
• Soft material: high speed
• Hard material: low speed
  The drill speed may need to be adjusted depending on the combination of material and drill bit diameter.

1.3 Drill packaging

When you go to the DIY store, you need to know which material you’re drilling, and what diameter and length drill you need: an image like the one above shows you what you can use the drill for. The diameter of the bit can usually be found in a box in the top-left corner, whilst the total and working length can be seen on the tape measure along the edge of the packaging.

The packaging shows you what you can use the drill bit for

1.4 Types of drilling and drill length

Sometimes you need to drill special types of holes or drill into unusual materials. Whatever your need, there’s a drill bit for the occasion.

1.4.1 Through holes

If you need to drill all the way through a material, you need to make a through hole – a good example of this is our hanging lights project. If you’re making a through hole, the drill bit should be longer than the thickness of the material.

1.4.2 Blind holes

Sometimes you don’t want to drill all the way through a material – for example, if you want to make invisible holes for hanging things up, as with our children's crown-shaped coat hook project. This is called a blind hole. It’s easy to make one in wood using a wood twist drill that is shorter than the thickness of the material. If you only have one drill bit that is longer than the material thickness, you can mark up the depth of the hole on the drill with tape. That way, you’ll know how far down to drill. If you need a drill with a bigger diameter, the Forstner bit is your best option.

You can mark the depth of a hole on a drill using tape

1.4.3 Tiefbohrung

For more information, please visit Leading Diamond Tools.

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Deep holes are similar to blind holes, except here the holes are particularly deep (at least five times deeper than the drill diameter). It’s the most common type of drilling if you want to mount something on the ceiling or wall. To give an example, you’ll need to drill deep holes to create your own vertical garden so that you can hang your project on the wall.

1.4.4 Drilling different-sized holes

You can use a step drill bit to quickly and precisely drill holes in non-ferrous metals, sheet steel and plastics. Thanks to the different diameters on the bit, you can drill holes ranging from 4–20 mm. A centring aid helps you to drill accurately.

It’s easiest to drill different-sized holes using a step drill bit

1.4.5 Drilling very large holes in wood

If you want to drill holes with a particularly large diameter (i.e. greater than 10 mm) in wood – which are also called blind holes – it’s best to use a Forstner bit. However, this is not suitable for particularly deep holes or through holes.

When drilling larger holes with diameters over 10 mm, it’s best to use a Forstner bit

2. Determine the depth of the hole

Not sure how deep to drill into a wall? Then base the depth on the wall anchors you want to use. As a rule of thumb, use the following formula to determine the depth of the hole: anchor length + 10 mm. This will ensure the anchor is completely out of sight later on.

If you're not using anchors, use the length and diameter of your screws to determine the drill bit length and the hole depth and diameter.

There are four main types of drill shanks

3. Which drill bit goes with which tool?

In addition to the various tips, drill bits also differ in terms of their shank shape. The shank is the part that is inserted into the drill chuck.

The different types of drill chucks include a self-centring/three-jaw chuck, which holds the drill bit in place with three "jaws" (points of attachment). By turning the chuck, it can be adapted to the diameter of the drill shank to firmly secure the bit. There are also various SDS chucks: here the drill bit snaps into place when it's inserted into the chuck, with no need to tighten the chuck or size it to the diameter of the drill shank.

There are four main types of drill shanks, each of which is suitable for specific tools:

• A round shank or cylindrical shank fits in almost all drills and impact drills.
• A hexagonal shank. Drill bits with this shank fit better in drills with three-jaw chucks. The hex shank is a special type of this shank and has an additional groove. As well as three-jaw chucks, it fits in SDS Quick and hex shank chucks.
• SDS Quick drill shanks fit in the Uneo cordless hammer drill and can also be used with all three-jaw chucks. This makes it the only shank that can be used with both a hammer drill and an impact drill.
• SDS Plus shanks are for use exclusively with SDS Plus drill chucks. These shanks cannot be used with other chucks such as the three-jaw chuck or other SDS chuck adapters.

We have created a table to help you decide which drill bit is right for your tool.

Die Übersicht zeigt dir, welcher Bohrer in welche Maschine passt. Anchors can help you fix items firmly and securely to the wall. © fischer

4. What is the right kind of wall anchor for my project?

To ensure pictures and shelves remain firmly on the wall, it’s important you use the right wall anchors. And the same rule applies as for drill bits: the anchor must be a good match for the material you’re drilling into.

The size of the anchor you need will depend on the size of the hole you’re drilling. For example, if you used a 6 mm drill bit, you should use the same size anchor. The screws you use should then have a slightly smaller diameter of around 4–5 mm, which is opposite to if you're not using anchors (see 1.2). The wall anchor packaging will usually specify the length and diameter of the screws you should use.

In general, a screw should always be slightly longer than the anchor to ensure it protrudes out from the wall. The longer an anchor is, the greater the load it can bear. So, the higher the load, the longer a screw should be in comparison to the anchor. Depending on the load, the screw can be between 3 mm (low load) and 16 mm (high load) longer.

Make sure you clean out the hole you've drilled before inserting the anchor. For example, you can use a handheld vacuum cleaner to remove any dust or remnants from drilling.

Use these anchors for plasterboard, concrete and masonry/brick walls

4.1 Different wall materials

Walls can be made from concrete, brick or panels such as plasterboard (drywall).

4.1.1 Standard or lightweight concrete

Concrete is an ideal material for fixing or hanging items onto. Long wall anchors made from plastic and chemical solutions such as grout, with the right equipment, are especially suitable for this type of wall. For lightweight concrete, which is lighter than standard concrete thanks to the addition of Styropor or pumice, are ideal. These expand as the screw is tightened, ensuring they are firmly anchored in the wall.

4.1.2 Brickwork (solid brick)

For walls made from solid brick (e.g. sand lime or clay bricks), almost all plastic anchors can be used.

4.1.3 Brickwork (perforated brick)

If your walls are made from perforated brick (similar to solid brick, but with evenly spaced cavities), you should try to use anchors that bridge the cavities or fill them in. Anchors with grout are ideal, as are plastic anchors that expand.

4.1.4 Panels (e.g. plasterboard)

For walls made from plasterboard, also known as drywall, you can use a special spiral-shaped drywall anchor made from metal or plastic. Unlike standard anchors, this does not expand. You should also use hollow wall anchors made from plastic or metal.

4.1.5 Hollow walls

For the best results with drywalls, you should use either a drywall anchor or a special hollow wall anchor made from plastic and metal. This is suitable for use with cavities of different sizes and holds securely. A universal anchor is also an option, as it expands behind panels and cavities.

Tip

IS THE WALL TOO SOFT?

If your wall is very soft and thin, it may help to make the hole you drill one millimetre smaller than the anchor – this ensures it sits even more firmly in the wall.

Re: Whhat drill for deep holes in wood?

king nero said:

Thanks for both your suggestions.

Don't really care for the "cleanliness" of the hole, so that's not an important factor.

DO I need cooling of any type? I guess no, as it's wood, but I also know a spade drill can get hot as fu(k when working it hard, playing havoc with the cutting edge.

What would be the advantage of an auger bit over a brad point bit?

Click to expand...

Auger bit (usually) self feeds. That little screw point on the tip of the auger bit pulls the bit in as it turns.

Auger bits can leave a rather rough hole.

For 'decent' general purpose holes in wood, I'd reach for a brad point bit almost every time. A 'regular' length brad point bit in 5/8" or 3/4" should just make it through your specified 5" thick workpiece. Or you can get the 'long' length bits, which in those diameters will usually be ~10-12" long.

http://wlfuller.com/html/long_length_brad.html

http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/drlbrad.html

As to cooling, any bit can get hot when used. Let the bit do the work, back it out as needed to remove 'swarf' (wood, in this case) and make your holes. Done.

No 'coolant' generally needed. A 'spray' of compressed air might help blow the wood chips out of the way (might be good or bad, depending on where the chips end up blowing into ).

Don't use cutting oil when drilling in wood.

If you wanted flat-bottom (mostly) blind holes, or overlapping holes, or pretty smooth holes, a Forstner bit would be the one to generally use. As mentioned, you have to back-out a Forstner bit much more often to clear the chips as you drill. For a 5" deep hole (might also need a 'shaft extension' for those depths) with those diameter bits (5/8" or 3/4"), I'd say you'd probably have to back out the bit about 5 times or so per hole (roughly once every rim depth of the bit). But you said you don't want/need 'clean' holes, so I wouldn't reach for the Forstner bit here.

Brad point bit. IMHO.

Auger bit (usually) self feeds. That little screw point on the tip of the auger bit pulls the bit in as it turns.Auger bits can leave a rather rough hole.For 'decent' general purpose holes in wood, I'd reach for a brad point bit almost every time. A 'regular' length brad point bit in 5/8" or 3/4" should just make it through your specified 5" thick workpiece. Or you can get the 'long' length bits, which in those diameters will usually be ~10-12" long.As to cooling, any bit can get hot when used. Let the bit do the work, back it out as needed to remove 'swarf' (wood, in this case) and make your holes. Done.No 'coolant' generally needed. A 'spray' of compressed air might help blow the wood chips out of the way (might be good or bad, depending on where the chips end up blowing into).Don't use cutting oil when drilling in wood.If you wanted flat-bottom (mostly) blind holes, or overlapping holes, or pretty smooth holes, a Forstner bit would be the one to generally use. As mentioned, you have to back-out a Forstner bit much more often to clear the chips as you drill. For a 5" deep hole (might also need a 'shaft extension' for those depths) with those diameter bits (5/8" or 3/4"), I'd say you'd probably have to back out the bit about 5 times or so per hole (roughly once every rim depth of the bit). But you said you don't want/need 'clean' holes, so I wouldn't reach for the Forstner bit here.Brad point bit. IMHO.

If you want to learn more, please visit our website blind hole drill bits supplier.