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115 or 125 cutting disc

Updated: 21 October 2026

You own a 115 mm angle grinder, and a 125 mm cutting disc is in the basket because the hole is 22.23 mm on both. That hole will pass the spindle. The guard decides whether the disc is legal to run. A 115 or 125 cutting disc is a size choice, not a quality ladder. The [cutting disc comparison](/hub/sanders/cutting-disc) lists which amazon.co.uk packs are which diameter. A qualifying purchase can earn us a commission at no extra cost to you. Peter F. used those listings, UK retail guides, and one review that refused a 4.5 inch guard. There was no lab cut. The wider order is in the [cutting disc buying guide](/hub/sanders/cutting-disc/sub/cutting-disc-buying-guide).

You own a 115 mm angle grinder, and a 125 mm cutting disc is in the basket because the hole is 22.23 mm on both. That hole will pass the spindle. The guard decides whether the disc is legal to run.

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
STONE REEF STONE REEF 125 × 1.0 mm, 25-pack

Rank 3

STONE REEF STONE REEF 125 × 1.0 mm, 25-pack
9.2/10about £12.99
View offer
On this page
  1. 1.Same hole, different guard
  2. 2.What 115 mm and 125 mm are for
  3. 3.What this comparison actually stocks
  4. 4.When to choose which

Same hole, different guard

The usual bore in this set is 22.23 mm, which UK grinders share across 115 mm, 125 mm and 230 mm. A larger disc can be fitted to a smaller machine if you take the guard off. HSE’s HSG17 treats the guard as part of how abrasive wheels are used, and overspeed as a separate way wheels fail. Taking the guard off to gain 10 mm of diameter is the mistake this page is for. A UK review of the STONE REEF 125 × 1.0 mm pack says the discs do not fit a 4.5 inch grinder unless the guard is removed. The listing bullet still says common 115 mm and 125 mm grinders. Follow the review, not the bullet. A 4.5 inch guard is the 115 mm guard. A 5 inch guard is the 125 mm guard.

What 115 mm and 125 mm are for

Toolstation’s guide puts 115 mm on accurate, lighter work and 125 mm in the middle as the more versatile size. ITS Hub’s buying guide gives indicative depths of about 30 mm on a 115 mm grinder and about 40 mm on a 125 mm grinder. Those millimetres are that guide’s table, not a British Standard. For bolts, brackets and sheet, 115 mm is enough. The marked speeds move the other way. Printed 115 mm maxima sit around 13,200–13,300 rpm. The two 125 mm listings sit at 12,200 rpm and 12,250 rpm. A 125 mm disc marked 12,200 rpm is not a spare wheel for a 115 mm grinder at 13,300 rpm. Match both the diameter and the rpm. Thickness stays about 1 mm on both sizes here.
Starrett Starrett 115 × 1 mm, 12-pack

Testsieger

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

What this comparison actually stocks

The 115 mm bonded packs run from Metabo at £4.95 and Starrett at £5.03 through to the Merryland 50-pack at £18.90. Where a speed is printed it is 13,200 or 13,300 rpm. Starrett and Faithfull do not print a maximum. The 125 mm packs are two. Merryland’s C13081042-50 is fifty 125 × 1.0 × 22.23 mm discs at £20.90, maximum 12,250 rpm, EN 12413. The 4.6 from 8,013 is the same block as the 115 mm Merryland packs. STONE REEF’s SR-1268 is twenty-five discs at £12.99, 12,200 rpm, 80 m/s, EN 12413, 4.6 from 276 on this ASIN. Bosch’s single disc is 230 × 3 mm at £2.41, not a third option for a 115 mm guard.

When to choose which

Choose a 115 mm pack when the guard is 115 mm, and a 125 mm pack only when the guard is 125 mm. Missing rpm on Starrett, no EN 12413 line on Metabo, and a shared Merryland review count are on the best cutting discs page. STONE REEF’s bullet is the one you should not trust on a 115 mm fit. Do not buy the 125 mm disc to get a deeper cut from the 115 mm grinder you already own. The extra depth in the ITS table assumes the larger machine. If you are about to mount either size, the how to use a cutting disc page is the sequence. Stainless chemistry stays off this page.

Common questions

Can I fit a 125 mm disc on a 115 mm grinder?
The bore often matches, and the disc can go on the spindle. A UK review of the STONE REEF 125 mm pack says it does not fit a 4.5 inch grinder unless the guard is removed. Do not remove the guard. Buy a 115 mm disc for that machine. The listing bullet that mentions both sizes does not override the review or the guard.
Do both sizes use a 22.23 mm bore?
In this comparison, yes, on the rows that state a bore. Starrett, Metabo, Faithfull, Merryland and STONE REEF print 22.23 mm. WORKPRO’s bullet prints 22 mm, MIDO prints 22.2 mm and 22.23 mm, and TechZone does not state a bore. A matching hole still leaves you with the guard and the rpm to check.
What rpm is typical for each size in this set?
Printed 115 mm maxima sit at 13,200 rpm on Metabo and 13,300 rpm on Merryland, MIDO, WORKPRO’s bullet and TechZone. WORKPRO’s spec table also says 13,000 rpm. The 125 mm packs are 12,250 rpm (Merryland) and 12,200 rpm (STONE REEF). Starrett, Faithfull and Bosch do not print a maximum on these listings. The disc’s own mark has to meet the grinder.
Which packs in this comparison are 125 mm?
Only two: Merryland B08KM1B7DX, fifty discs at £20.90, and STONE REEF B0DMVSF9NW, twenty-five discs at £12.99. Both are 125 × 1.0 × 22.23 mm and both name EN 12413. Every other bonded pack here is 115 mm, except the Bosch disc, which is 230 mm.
Is 115 mm enough for bolts and brackets?
Yes, for the jobs UK reviews in the 115 mm packs actually describe: a 10 mm bolt, exhaust bolts, 2 mm plate, sills and thin galvanised sheet. You do not need a 125 mm disc for that work. Move up a grinder size when the cut needs the extra reach those retail guides describe, and buy the matching disc at the same time.

Related pages

230mm metal cutting disc

Cutting disc

Best cutting discs for steel on a UK angle grinder

Cutting disc buying guide: diameter, metal and speed

How to use a cutting disc: guard, flanges and the cut

Stainless steel cutting disc: inox and contamination

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)