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How to use a cutting disc

Updated: 21 October 2026

You have a new pack on the bench and a bolt, a bracket or a length of tube in the vice. How to use a cutting disc, on a UK angle grinder, is a straight cut with the guard on, after you have checked the diameter and the date. Prices and which pack is which sit in the [cutting disc comparison](/hub/sanders/cutting-disc). A qualifying purchase can earn us a commission at no extra cost to you. Peter F. followed HSE and FEPA guidance plus the UK review notes on 19 October 2026. We did not run the grinder. If you are still choosing a pack, use the [cutting disc buying guide](/hub/sanders/cutting-disc/sub/cutting-disc-buying-guide) first.

You have a new pack on the bench and a bolt, a bracket or a length of tube in the vice.

Our top picks

Starrett Starrett 115 × 1 mm, 12-pack

Best overall

Starrett Starrett 115 × 1 mm, 12-pack
9.4/10about £5.03
View offer
Merryland Merryland 115 × 1.0 mm, 50-pack

Best value

Merryland Merryland 115 × 1.0 mm, 50-pack
9.2/10about £18.90
View offer
Bosch Bosch PRO 230 × 3 mm, single

Rank 3

Bosch Bosch PRO 230 × 3 mm, single
9.2/10about £2.41
View offer
On this page
  1. 1.Check the disc before it goes near the spindle
  2. 2.Mount it with the guard and the proper spanner
  3. 3.Cut straight and let the disc work
  4. 4.Stop, and when not to do the job yourself

Check the disc before it goes near the spindle

Read the diameter against the guard, not against the hole. A 22.23 mm bore fits the usual spindle on a 115 mm, 125 mm and 230 mm grinder, and the disc can still be the wrong size. A UK review of the STONE REEF 125 mm pack says it will not fit a 4.5 inch grinder unless the guard comes off. Leave the guard on and change the disc. The marked maximum rpm has to be at least the speed on your machine. Where this set prints a figure, 115 mm wheels cluster around 13,300 rpm and 125 mm wheels around 12,200 rpm. Starrett, Faithfull and the Bosch 230 mm disc do not print a maximum on the listing, so you read the disc itself. Look for cracks, a warp, or a disc that was dropped. HSE’s HSG17 says organic-bonded wheels for hand-held use carry a use-by date of three years from manufacture. If the date has passed, the disc is finished. One Starrett reviewer reported two of three thin discs shattering after kickback.

Mount it with the guard and the proper spanner

The disc has to slide onto the spindle without being forced. FEPA’s mounting rules are plain: flanges that match the wheel, and the nut tightened only with the pin spanner that came with the grinder. Flat cut-off wheels in this set sit between flat flanges. The Bosch 230 mm listing is a depressed-centre wheel, so the flange orientation is the one in that grinder’s manual. A rusty flange that stands proud is a reason to stop. Fit the guard between you and the disc, then run the grinder for at least 30 seconds with the wheel behind the guard before it touches the work. FEPA and the Abrasives Safety page both give that trial. Stand out of the plane of the disc. If it vibrates, or the guard will not close, take it off. Secure the work. A tube that can roll will pinch the disc.
Starrett Starrett 115 × 1 mm, 12-pack

Testsieger

Starrett Starrett 115 × 1 mm, 12-pack
9.4/10about £5.03
View offer

Cut straight and let the disc work

A cutting disc cuts in its own plane. Twisting to hurry a bolt, or laying the face of the disc on a weld, is side load. FEPA’s leaflet says not to grind with a cutting wheel. A UK review of TechZone says the first 0.8 mm disc broke in the middle on handrail brackets. WORKPRO reviews report a centre that broke up. For a 10 mm bolt, a Starrett reviewer described a cut in seconds on an Einhell 115 mm grinder. Clamp the offcut so it cannot close the kerf. If the grinder kicks, release the trigger. A fresh disc from the same pack does not fix a cut that is binding.

Stop, and when not to do the job yourself

Stop when the disc is cracked, out of date, or when you cannot clamp the piece, the cut is overhead, or the line is a gas pipe or anything structural. If the disc is the wrong diameter, do not take the guard off. The best cutting discs page is the shortlist once the size is settled, and the 115 or 125 cutting disc page is the one to read before a 125 mm pack goes near a 4.5 inch grinder.

Common questions

Which way round do the flanges go?
Flat cut-off wheels sit between flat flanges. A depressed-centre wheel, such as the Bosch 230 mm disc in this set, needs the orientation in the grinder manual. The disc must slide on. A flange that is rusty or proud is a reason to stop, not a reason to nip the nut harder. A hammer is never the tool for that nut.
Can I grind a weld with a cutting disc?
No. A cutting disc is for a straight cut. Grinding uses the face of a thicker wheel at a shallow angle, and FEPA tells you not to grind with a cut-off wheel. Side load is how the 0.8 mm and 1 mm discs in the UK reviews break. If the weld needs cleaning, fit a grinding disc rated for that grinder, with its own guard setup.
What eye protection is cited for dry grinding?
HSG17 names eye protectors to BS EN 166 for dry grinding. A metal cutting disc throws sparks in the same way, so use that protection for the cut as well. The standard is the one HSE cites. Keep fuel and loose clothing out of the spark line.
What do I do if the disc kicks?
Release the trigger and let the grinder stop. Do not twist the disc to free it. Kickback is how thin wheels shatter: one Starrett review describes two of three discs breaking after the grinder kicked on thin blades. Check the disc for cracks before you think about another pass, and check that the work is still clamped.
Does a householder need an abrasive-wheel certificate?
If you employ people, PUWER and HSG17 expect practical training to mount wheels. Cutting a bolt at home does not, by itself, put you under that employer duty. The failures are the same either way: overspeed, no guard, side load, a dropped or out-of-date disc. Follow the mounting steps on this page, and hand over structural steel, fuel lines, and cuts you cannot clamp.

Related pages

Stainless steel cutting disc

Cutting disc

115 or 125 cutting disc: which guard will close over

Best cutting discs for steel on a UK angle grinder

Cutting disc buying guide: diameter, metal and speed

Sources

Sources taken from the research digest. Prices, stars and review counts are the stored amazon.co.uk listing figures from 19 October 2026.

  1. HSE HSG17 — Safety in the use of abrasive wheels (retrieved 21.10.2026)
  2. HSE — PUWER overview (retrieved 21.10.2026)
  3. FEPA — Safety leaflet, bonded abrasives (retrieved 21.10.2026)
  4. Abrasives Safety — Reinforced bonded wheels (retrieved 21.10.2026)
  5. Engweld — How to choose a cutting disc (retrieved 21.10.2026)
  6. Saw-Tech UK — Choosing a cutting disc (retrieved 21.10.2026)
  7. Cutwel UK — Grinding discs guide (retrieved 21.10.2026)
  8. Toolstation — Angle grinder buying guide (retrieved 21.10.2026)