Independent comparisons. We may earn from shop links. More info

How to use a tap and die set

Updated: 17.10.2026

The hole in front of you is about to become an M6 thread, and the obvious drill is 6 mm. That drill is too big. The tap will leave a shallow ripple, and the bolt will strip. This page is the hand sequence for a metric set: drill size, a square start, lubricant, and the moment you stop. The twelve kits are on our [tap and die set comparison](/hub/diy-supplies/tap-and-die-set) if you do not own one yet. Stainless practice is on the [tap and die set for stainless steel](/hub/diy-supplies/tap-and-die-set/sub/tap-and-die-set-stainless-steel) page, and form identification is on the [metric or Whitworth](/hub/diy-supplies/tap-and-die-set/sub/tap-and-die-set-metric-or-whitworth) page. Peter F. followed UK charts and a hand-tap sheet, not a laboratory trial. The listing capture is 15 October 2026.

The hole in front of you is about to become an M6 thread, and the obvious drill is 6 mm. That drill is too big. The tap will leave a shallow ripple, and the bolt will strip.

Our top picks

Mannesmann Mannesmann 32-piece M3–M12

Best overall

Mannesmann Mannesmann 32-piece M3–M12
8.4/10about £18.92
View offer
Gunpla Gunpla 40-piece OT569

Alternative

Gunpla Gunpla 40-piece OT569
7.9/10about £25.60
View offer
Gunpla Gunpla 20-piece M3–M12

Preis-Tipp

Gunpla Gunpla 20-piece M3–M12
7.7/10about £16.98
View offer
On this page
  1. 1.Drill the tapping size, not the bolt size
  2. 2.Start with the taper and keep it square
  3. 3.Run the die from the chamfered side
  4. 4.When to stop and call someone else

Drill the tapping size, not the bolt size

A tapping drill is smaller than the bolt, because the tap has to leave metal for the flanks. FWB and Optimas print the same coarse column: 2.5 mm for M3, 3.3 mm for M4, 4.2 mm for M5, 5.0 mm for M6, 6.8 mm for M8, 8.5 mm for M10 and 10.2 mm for M12. The rule of thumb is nominal diameter minus pitch, so M6 × 1.0 is 5 mm, not 6 mm. Fine pitches need their own column. Clamp the work. Sealey's AK301 sheet says not to hold the part in your hand, because a tap catches and the wrench follows. Deburr the mouth so the taper can enter. Wear eye protection. Do not wear gloves at a rotating drill. The Health and Safety Executive's EIS16 guidance is that a glove winds in.

Start with the taper and keep it square

UK serial sets use three tools. The taper starts the thread, the second follows, and the plug finishes a blind hole. American lists often swap the last two names. One tap per size can chase a through-thread. It cannot finish a blind hole. Which contents you bought is the tap and die set buying guide. Oil the tap and the hole before the first turn. Sealey's rhythm is about half a turn forward and a quarter turn back, so the chip breaks. Keep the shank square. A start that leans cuts a drunken thread. For a blind hole, stop before the nose hits the bottom. The next hard turn is the one that snaps the tap.
Mannesmann Mannesmann 32-piece M3–M12

Testsieger

Mannesmann Mannesmann 32-piece M3–M12
8.4/10about £18.92
View offer

Run the die from the chamfered side

A die cuts or cleans the external thread. Most dies in these budget sets are solid, not split, so you cannot close them. A Mannesmann reviewer expected split dies from the picture and did not get them. The nut is the gauge. Chamfer the end of the bar and lead with the chamfered face of the die. Start on the flat face and the die skates. Use the same oil and the same half-turn rhythm. The thread is finished when the real nut runs on by hand. Do not fit a longer bar. If the fit is loose, a second pass will not put metal back.

When to stop and call someone else

Stop when the tap goes suddenly tight. Reverse it. If it will not move, leave it. A machine shop can remove a broken tap. Do not drill the stub out with the bit that made the hole. Brakes, steering, suspension, gas fittings and anything under pressure are not practice pieces. If you cannot tell metric from Whitworth, do not guess with the die that almost fits. A cordless drill is the right tool for the hole and the wrong tool for the tap. These are square-shank hand cutters. Spinning one removes the quarter-turn reverse, which is how taps below M5 snap. A qualifying purchase from the main comparison can earn us a commission at no extra cost to you.

Common questions

What drill do I use for M6, M8 and M10?
For coarse metric, use 5.0 mm for M6 × 1.0, 6.8 mm for M8 × 1.25, and 8.5 mm for M10 × 1.5. FWB and Optimas print those figures. An M6 hole drilled at 6 mm leaves too little metal. M12 × 1.75 is 10.2 mm on the same charts.
Which tap do I start with?
Start with the taper, the longest lead, so the thread begins square. Use the plug, the shortest lead, only to finish a blind hole, and do not drive it into the bottom. If the set has one tap per size, stay with a through-thread that already exists.
How far do I turn before I back off?
Once the tap has bitten, turn about half a turn forward, then about a quarter turn back to break the chip. That is the rhythm in Sealey's AK301 instructions. If the forward turn suddenly needs more force, stop. A longer bar on a tight tap is how the shank snaps.
Which way does the die face?
Lead with the chamfered side of the die, onto a bar you have already chamfered. Starting on the flat side lets the die skate. Solid dies in these sets do not adjust, so the real nut is the only gauge that matters.
What fluid should I use?
Use a cutting oil or paste on the tap, the die and the hole before you start, and again when you clear chips. Reviewers blame dry use when edges chip, including on aluminium. A general water-displacing spray is not the fluid for stainless.
Can I run the tap in a cordless drill?
Use the drill for the hole only. These taps have a square shank for a hand wrench. A drill removes the quarter-turn reverse that breaks the chip, and it is how small taps snap, especially below M5. Turn the wrench yourself.
What if the tap suddenly goes tight?
Stop and try to reverse it by hand. Tightness means a packed flute, a tap at the bottom, or a hole that was too small. If it will not unscrew, leave the stub for a machine shop. If the thread is on brakes, steering or gas, stopping is the repair.

Related pages

Best tap and die set

Tap and die set

Tap and die set buying guide: form, pitch and taps

Metric or Whitworth tap and die: 55 versus 60 degrees

Tap and die set for stainless steel: skip the claim

Sources

Public UK sources on thread form, tapping drills, work equipment and satisfactory quality. Listing prices and star counts are from the amazon.co.uk extracts dated 15 October 2026. Prices move.

  1. HSE, PUWER overview (retrieved 15 October 2026)
  2. HSE, using the right type of PPE (retrieved 15 October 2026)
  3. HSE EIS16, gloves and drilling machines (retrieved 15 October 2026)
  4. Consumer Rights Act 2015, section 9 (retrieved 15 October 2026)
  5. RoyMech, screw threads and BS 3643 (retrieved 15 October 2026)
  6. FWB, tapping and thread dimensions (retrieved 15 October 2026)
  7. Optimas, tapping sizes (retrieved 15 October 2026)
  8. Protool, thread forms (retrieved 15 October 2026)