How to use a tap and die
Updated: October 2026
The bolt has gone in crooked, and another turn with the spanner will take what thread is left. How to use a tap and die, for one metric hole, is a drill size, a square start, and a stop when the tool stops cutting. This page is that sequence for a hand set you already own. It does not rank the twelve listings in the [taps and dies comparison](/hub/drilling-and-accessories/taps-and-dies). The drill figures below come from the UK chart used for this page. A qualifying purchase can earn a commission at no extra cost to you.
The bolt has gone in crooked, and another turn with the spanner will take what thread is left. How to use a tap and die, for one metric hole, is a drill size, a square start, and a stop when the tool stops cutting.
The bolt has gone in crooked, and another turn with the spanner will take what thread is left. How to use a tap and die, for one metric hole, is a drill size, a square start, and a stop when the tool stops cutting. This page is that sequence for a hand set you already own. It does not rank the twelve listings in the taps and dies comparison. The drill figures below come from the UK chart used for this page. A qualifying purchase can earn a commission at no extra cost to you.
Our top picks
| Badge | Product | Taps per size | Dies included | Set type | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Gunpla Gunpla 32-piece metric tap and die set | 3 | Yes | Taps and dies | 8.6 | about £25.98 | View offer |
| Best value |  GreeSuit GreeSuit 32-piece tap and die set 32-SL | 3 | Yes | Taps and dies | 8.1 | about £21.86 | View offer |
| Alternative |  CYH CYH ratchet tap wrench with five taps | 1 | No | Taps only | 6.8 | about £6.46 | View offer |
On this page
Drill the tapping size, not the bolt size
The hole has to be smaller than the bolt. For ISO metric coarse threads, SAMS Fabrications publishes M6 at 5.0 mm, M8 at 6.8 mm, M10 at 8.5 mm and M12 at 10.2 mm. The same chart gives M3 at 2.5 mm, M4 at 3.3 mm and M5 at 4.2 mm. A rule of thumb is diameter minus pitch. It is a rule of thumb, not a second standard, and it is the coarse pitch only. An M8 × 1.0 hole is not the 6.8 mm hole. If you are not sure the bolt is metric, leave the drill in the box. That check is on the metric or imperial page.
Taper, then second, then bottoming
Start with the taper, the tap with the long chamfer. In British usage the plug is the bottoming tap that finishes a blind hole. In North American lists, plug is the middle one. If your set prints the word and nothing else, look at the chamfer and start with the longest lead. A through hole can finish on the taper if that lead passes out of the far side. A blind hole needs the later taps. Do not drive the tap into the bottom. The CYH listing is five single taps a reviewer called tapers. One taper will not finish a blind hole.
Cut, then back off
Clamp the work. A tap that walks cuts a leaning thread. Eye protection is the practical control at home. At work, training under the Provision and Use of Work Equipment Regulations sits with the employer. Use a cutting fluid, and keep that oil off your skin.
Stand the taper square to the face before the thread locks in. For a right-hand thread, turn clockwise, then reverse to break the chip. Ultimate Handyman describes about two turns forward and one back. OffBeat Bikes describes reversing about every half turn. Those are two workshop rhythms, not one precise rule. Clear the flutes as you go. If the wrench will not hold the square drive, stop. Pliers round the square that the proper wrench has already failed to grip.
Starting a die
Chamfer the end of the rod so the die has a lead to pick up. Hagerty’s account puts the lettering upwards, oils the cut, and backs off to break the chip. Check the result against a known nut of that pitch. A split die opens for the first pass, then closes. If there is no slot, you cannot ease it. Reviews of the Gunpla 40-piece and the GreeSuit 32-SL describe dies with no split. Start the die square. On a vehicle, the car repairs page draws the line for brakes, steering and wheel studs.
When you stop
Stop when the tap stops cutting. A rising effort, a squeak, or a sudden loose spin means the tap has jammed or broken. Turning harder drives a broken piece further in. Erodatools, in South Yorkshire, states that spark erosion is a workshop method when a broken tap cannot be removed another way. This page does not describe that process. If the part is a brake, a steering joint, a suspension fastener or a gas fitting, do not start the hole.
Common questions
What drill do I use for M6, M8, M10 and M12?
For metric coarse threads, the SAMS chart gives M6 as 5.0 mm, M8 as 6.8 mm, M10 as 8.5 mm and M12 as 10.2 mm. Those holes are smaller than the bolts. An 8 mm drill under an M8 tap leaves no metal for a coarse thread. Fine pitches are not those numbers. Measure the pitch before you pick the drill.
Do I start with the plug tap?
Start with the taper. In British usage the plug is the bottoming tap, and it comes last on a blind hole, after the second tap. Starting with the short lead asks it to bite a full thread at once. If your set prints plug and does not say which lead that means, find the longest chamfer and start there. A through hole can often finish on that taper alone.
How often do I reverse the tap?
Often enough to break the chip and clear the flutes. Ultimate Handyman describes about two turns forward and one back. OffBeat Bikes describes a reverse about every half turn. Use one of those rhythms. Do not treat them as a single exact count. If the tap will not turn backwards, stop. Forcing the reverse is how the square drive rounds off.
What if I only have one tap in that size?
Use it on a through hole, where the lead can pass out of the far side, or to tidy a thread that is already cut. A reviewer of the CYH taps called them tapers, one per size from M3 to M8, with no die in the package. That arrangement will not finish a blind hole. If the hole must be blind, get a second and a bottoming tap of that pitch before you drill.
The tap has snapped. Do I keep turning?
Stop. The broken piece is harder than most of the metal around it, and another turn seats it deeper. Spark erosion is a workshop method for a tap that will not come out another way. Erodatools in South Yorkshire describes that service. Do not drill the stub out at home. If the hole is in a brake, a steering part or a gas fitting, the workshop was the right place before the tap snapped.
Related pages
Sources
Sources from the research digest. amazon.co.uk listings in this category were captured on 15 October 2026. We did not run a laboratory test.
- Ultimate Handyman, Tap and Die (retrieved 15 October 2026)
- Grove Components, Tap Terminology (retrieved 15 October 2026)
- PG Merlin, The different types of taps (retrieved 15 October 2026)
- Protool, thread forms (retrieved 15 October 2026)
- RS, guide to metric bolt sizes (retrieved 15 October 2026)
- ISO 529:2017, short machine and hand taps (retrieved 15 October 2026)
- HSE, PUWER overview (retrieved 15 October 2026)
- Consumer Rights Act 2015, section 22 (retrieved 15 October 2026)