1mm or 3mm, Inox or Flap? Pick the Right Grinder Disc First Time

Stand at a rack of grinder discs and the choices pile up: 1mm or 3mm, inox or standard, flap or grinding disc. Pick wrong and it cuts slowly, wears out fast or won't fit. The short answer: match the disc to the material and the job, then check diameter, bore, speed rating and date.

PartsForMachines offers 483 products from Abracs, Sealey, Draper, Osborn, SIP and Sykes Pickavant in its cutting and grinding range.

Which Cutting Disc Do I Need for Sheet, Steel or Stainless?

Use an extra-thin disc for sheet and light sections, a 3mm disc for everyday cutting and an inox-rated disc for stainless. At 1.0 to 1.6mm, extra-thin discs make accurate cuts in sheet, thin-wall tube and profiles such as small angle iron, with very little vibration, less heat and less burr. The PHET11510FI 1mm extra-thin disc handles sheet, mild steel and stainless. Thicker 3mm discs suit jobs such as cutting pipe and rebar.

An inox disc is made without iron, sulphur or chlorine, so it cuts stainless without leaving rust or contamination. Many thin inox discs cut mild steel too, so check the label: one disc may cover both jobs.

Why Do My Cutting Discs Wear Out So Fast?

Often because the disc is being forced or tilted. Pushing harder mainly adds heat, and heat shortens disc life, so let the disc do the work: if the motor slows in the cut, ease off.

A cutting disc is made to cut with its edge only. If yours wears on its side, it is being tilted, pushed sideways or used to grind. Keep it square to the work, never grind with it, and never twist it to steer a wandering cut back on line. It will bind, and side loading can shatter it.

Is My Cutting Disc Safe to Use?

Only if it is in date, undamaged and rated for your grinder. The month and year stamped on the metal ring, such as V07/2025, is an expiry date, so don't use the disc after it. Resin-bonded discs for hand-held grinders can be used for up to three years from manufacture. Bin any disc that is cracked, chipped or has been dropped.

Then check the speed: the maximum speed marked on the disc must be at least the top speed marked on your grinder. Larger discs are rated lower: the 3mm ProFlex discs are rated to 13,200rpm at 115mm but only 6,600rpm at 230mm.

Flap Disc or Grinding Disc: Which Should I Use?

Use a grinding disc for heavy removal and a flap disc to grind and finish in one go. A depressed-centre grinding disc, 6 to 7mm thick, is built for aggressive work such as grinding off welds and smoothing steel. A flap disc cuts like a sanding disc but lasts more like a grinding disc, because its bonded flaps wear down to reveal fresh abrasive.

Flat (Type 27) flap discs suit flat surfaces and leave a more even finish. Conical (Type 29) discs, such as the 85724 60-grit zirconium flap disc, suit edges, weld seams and contours.

What Should I Check Before I Buy?

• The material and the job: cutting, heavy grinding, weld blending or finishing.
• Diameter and bore to suit your grinder or saw.
• A speed rating at least equal to the tool's top speed.
• Thickness for cutting discs; grit, abrasive and shape for flap discs.
• The EN 12413 marking on cutting and grinding discs, and a pack size you will use before the date, from single discs to packs of 100.

Not sure which disc suits the job? Browse the cutting and grinding range or contact the PartsForMachines team by WhatsApp, telephone or email with your grinder size and the material you are cutting.

Pack sizes, delivery options and returns terms are shown on each product page. A 30-day return policy applies to eligible items.

Frequently Asked Questions

Will metal cutting discs fit a grinder I have only used on stone?

Yes, if the diameter and bore match. A standard 4½in grinder takes 115mm discs with a 22mm bore, sometimes given as 22.23mm. Stone and metal discs share sizes but each is made for its own material, so check the label and speed rating.

Can I still get discs for an old 100mm angle grinder?

Yes. Cutting, grinding and flap discs all come in a 100mm size with a 16mm bore, such as the PTC/100CT 1.6mm cutting disc for mild steel and stainless. Check the bore and speed rating against your grinder before you order.

Which disc does a large metal chop saw take?

A 355mm (14in) cutting disc is the standard size for large metal chop saws. The PTC/355C 3mm cutting disc, for example, has a 25.4mm bore. Check the bore and speed rating against the markings on your saw.

Which flap disc grit should I use for weld work?

Mostly 60 grit. Start at 40 for heavy removal, do the main work at 60, refine at 80 and finish at 120. The FD115MIX mixed-grit zirconium flap disc pack holds all four grades.

Should I buy zirconium or aluminium oxide flap discs?

Zirconium for steel and stainless: it is the more durable choice for heavy removal and weld grinding. Aluminium oxide suits everyday preparation on softer ferrous and non-ferrous metals; it costs less but has a shorter life.

Is it worth having a different disc for each metal?

Not always. If you switch materials often, a universal 115 x 1.6mm disc cuts mild steel, stainless, aluminium and masonry, so you are not swapping discs mid-job. Dedicated discs still earn a place, such as grinding discs made for aluminium.

Do cheap cutting discs last as long as expensive ones?

Not necessarily, and price per disc won't tell you. Compare cost per cut by counting how many cuts a pack really gives on your usual job, and check your technique first, because forcing any disc shortens its life.

Can I take the guard off to use a thin slitting disc?

No. Keep the guard between you and the disc, because it helps contain the fragments if the disc breaks, and wear goggles or a full face shield for hand-held work.

How do I fit a new disc safely?

Unplug the grinder or remove its battery. Check the disc for chips and cracks and the flanges for damage, and fit it with the guard between you and the disc. Run it at full speed for a minute or more, standing to one side.

Does the expiry date still count if discs are kept in a damp workshop?

Not really. The date assumes good storage, so a disc kept damp or through big temperature swings is not one to trust, even in date. Store discs dry, frost-free, at a steady temperature and lying flat.