Flap Discs for Stainless Steel How to Choose the Best

By Bill Byers / April 27, 2019
Flap Discs For Stainless Steel Title Image

Flap Discs for Stainless Steel:

    1. Are made for and to grind on stainless steel
    2. Have coatings or resins on their surface to keep your stainless steel cool while grinding
    3. Are contaminant free with less than 0.1% iron, sulfur or chlorine
    4. Won’t gouge or scratch your precious stainless steel and glide smoothly across the surface even in a novice user’s hands.

Before Choosing a Flap Disc, Understand Stainless Steel

Stainless Steel is available in many types depending on the properties needed. The one thing that all the types of stainless steel have in common is their mark or stain resistance – hence the name.

This means stainless steel retains its shiny look even when exposed to conditions that would have unprotected mild steel rusting and crumbling, for example, marine environments, through to cooking and food preparation and in medical applications.

This relates to your choice of flap disc how?

Using the wrong flap disc on your stainless steel can ruin its special properties.

What Else to Understand Before you Select Your Flap Disc

Stainless steel is harder than low carbon or mild steel, making it more difficult to grind on. Another reason to select the right flap disc.

It is also an expensive material. Using an incompatible flap disc will as a minimum cost you more time and effort and at worst wreck the stainless steel.

Flap Disc On Stainless 1

Flap Disc Working On Stainless Steel

What are the Wrong Flap Discs to Use on Stainless Steel?

Flap discs that are high in iron or other contaminants. A cheap flap disc designed for using on low carbon or mild steel is likely to leave a layer of fine particles on your pricey stainless steel.

And why does this matter?

These particles are impurities to stainless steel. And what is worse is those impurities are unlikely to show up until after your steel is exposed to the elements the stainless steel was chosen for in the first place.

For example these particles will rust outside when exposed to the weather. Or worse the stainless food container you welded reacts to the acids in the food. Your weld joint fails because the foreign particles allow the food to attack the weld, not to mention the hygiene exposure.

Or you grinded on a joint to prepare it for welding, now you find it difficult to strike a good arc, due to tainting from using the wrong flap disc on the joint.

Stainless steel is sensitive to the wrong kind of heat. Incompatible flap discs run hot. The results of which are scorch marks on your stainless steel.

Scorch marks that indicate you now have intergranular corrosion. And you are now in a whole other world of problems.

Intergranular corrosion is where the metal elements that give stainless steels its properties such as chromium, nickel and molybdenum, move away from areas of high heat. The result is cracking at a granular level and those sections of the stainless steel loosing it’s anti corrosion.

And you can heat up the incompatible flap disc so much it fails, breaks apart, flying pieces of flap disc material all over your working area.

Best Flap Disc for Stainless Steel

To help you in your search for the best stainless steel flap disc, I’ve collated a few I think are good and certainly worth your consideration. They are all available on Amazon so do feel free to click on the links and check them out. One of them may fit the bill for you.

  1. *Enduro-Flex Stainless 15Q458 Flap Disc

(*Paid Link)

Cost Indication: $$$

A top end flap disc made for using on stainless steel. A type 29, flat profiled flap disc available with one grit surface.

80 grit with a Zirconia coated surface. Best used for the blending in of your weld after welding and for finishing off leaving behind a smooth surface.

4 1/2 inch sized flap disc with a 7/8 inch arbor hole.

The flap disc has a wood fiber backing that is trimmable giving this flap disc a long life on your stainless steel. Do remember to trim to extend the life of the Enduro-Flex Stainless flap disc.

Pack of 10.

  1. *Weiler 51108 Tiger Paw High Performance Abrasive Flap Disc

(*Paid Link)

Cost Indication: $$

This Tiger Paw flap disc is well priced for a flap disc for stainless steel. They are available in grit sizes 36, 40 and 60 Grit. Shape types available: type 27, 29 and 27 in a high density flap disc.

Has a Zirconia Alumina surface, which is contaminant free for use on stainless steel. The available grit surfaces mean that you can prepare and clean your stainless steel for MIG or flux core welding. And after welding, level that weld bead and remove spatter.

4 1/2 inch size with a 7/8″ arbor hole.

A pack of 10.

YouTube Video on the Weiler Tiger Paw

This YouTube video illustrates the flexibility of the Tiger Paw flap discs. This 2 minute 18 second video is worth a watch.

Weiler’s Tiger Paw High Performance Flap Disc

Video Credit: Weiler Abrasives Group

  1. *United Abrasives SAIT 71205 Encore Flap Disc

(*Paid Link)

Cost Indication: $$

Another well priced stainless steel flap disc the SAIT Encore is available in grit sizes 40, 60 and 80 grit. Available in Type 27, a flat shaped flap disc.

4 1/2 inch and 5 inch sizes with a 5/8th inch arbor hole.

With a Zirconia surface that is contaminant free (< 0.1% iron, sulfur and chlorine) for use on stainless steel.

Use for cleaning, preparing, weld grinding, blending and deburring.

The SAIT Encore has larger flaps and more flaps around its diameter than its competition. More flaps and larger flaps mean more grinding and a long life for this flap disc.

The Properties of Flap Discs For Stainless Steel

Flap discs designed for stainless steel will clearly say so. Yes they will be a bit more expensive than ordinary flap discs designed for mild steel but there is a reason for that.

Firstly they will be manufactured to be low in iron or other spoiling materials known to affect your special stainless steel. Or they may be marked as INOX (from the French inoxydable) meaning inoxidizable – resistant to corrosion.

Also look for the description saying that the flap discs are contaminant free or described as < 0.1% iron, sulfur and chlorine. Then you’ll be in the ball park.

In addition the best flap disc for stainless steel will also have resins and or special proprietary surfaces that are designed to run cool, taking away the risk of intergranular corrosion.

The grit used on the flap disc will be tough enough to grind on your stainless steel effectively yet not gouge into your precious stainless steel surface.

A specialist flap disc designed for stainless steel will also be more forgiving on the lack of grinding skills of a novice grinder user as they are made to run cooler.

Flap Disc On Stainless

Points to Remember When Using your Flap Disc on Stainless Steel

You have chosen your flap disc and it is made for stainless steel. Great!

It may well be able to grind on other metals. And because these discs are pricey you may be tempted to share across the different metal types. – lint to flap discs for metal

My best advice is don’t.

Keep your flap disc for stainless steel only for stainless steel.

Mark it to identify it and place it away where you’re not risking contamination from other flap discs used on other metals.

Use your flap disc for stainless steel with a light pressure, let the disc do its work. Move evenly across the surface and keep your stainless steel as cool as possible.

When To Use Flap Discs On Your Stainless Steel

  1. Before you Weld

The surface of the stainless steel may well look fine and clean enough yet still have a layer of oil or other less obvious dirt on the surface. And that includes stainless steel delivered straight from the supplier. It is best to use a flap disc to clean the stainless steel, after using a solvent wipe to remove any oil.

Whether you are welding MIG, TIG, welding with flux core wire, or stick welding, clean off the metal surface.

Cleaned Stainless Steel v Factory Condition

Stainless Steel. On left flap disc used to clean. On the right new Stainless Steel as factory delivered.

Alternatively your stainless steel may have a little dirt or a few scratches on the surface and you could use a flap disc to clean all that off before you weld.

In addition, the edges of your joint may need deburring and smoothing down.

  1. After Weld Clean Up

Flatten down that weld bead. Blend your weld into the surrounding stainless steel for a smooth consistent appearance. Remove spots of spatter leaving the surface clear and shiny ready for polishing.

Stainless Steel Flap Discs Grit Sizes

Flap discs will state the size and type of grit used on the flap disc.

Grit sizes range from 24 to 120 grit and above. The lower the grit number the coarser and more aggressive it is on the stainless steel.

As a home hobby user the grit sizes you are likely to use for your stainless steel are:

36 or 40 Grit, used for the beveling of your stainless steel. Perhaps some dirt removal if your stainless is particularly dirty. Usually for weld removal. This is a course grit size and is used when heavier removal is wanted.

60 grit, is used for lighter clean up and dirt removal. Medium grinding.

80 Grit is used for finishing off, blending of your weld into the surrounding stainless steel.

120 grit for fine light finishing.

In addition to grit size the type of grit used is important. I go into that next.

Flap Disc Surface Types for Stainless Steel

There are two main types of surfaces used.

Zirconia – Works well on the heat sensitive stainless steel. Strong enough to grind on the stainless steel and with a good flap disc design and a heat resistant coating this surface type works well on stainless staying sharp through the life of the flap disc.

Ceramic – Is more resistant to heat than zirconia. It is more expensive and a high quality surface for your stainless steel. Look for stainless steel rated ceramic flap discs.

Stainless Steel Flap Disc Shapes and Density

And yes flap discs for stainless steel come in two main shapes. One aimed at those flat surfaces of your steel and for blending. The other has a more shaped and angled surface and is better for curves.

Type 27 are the flat flap discs. That said they do have a small angle on the face of 5 to 15 degrees. And are better for grinding into tight corners.

Type 29 are more shaped with a 15 to a 35 degree angle on the face. They are have a more aggressive grinding action. Used for covering large surfaces quickly where you have more dirt. And on those contoured surfaces.

A flap disc described as standard compared to jumbo has different flap densities.

A standard density flap disc is more aggressive when grinding. Use when you need to work quickly.

A Jumbo flap or one described as high density has thicker flaps, they are deeper, softer and last longer. Select those when working on curved surfaces and use when you need fine blending on your weld.

Last Words

I hope my article Flap Disc for Stainless Steel How to Choose The Best, has helped you find out about and assisted you in choosing the right flap disc for your stainless steel project. I wish you easy preparation, good strong stainless steel welds and beautiful finishes.