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tell me about flap discs | The Garage Journal

01 Sep.,2025

tell me about flap discs | The Garage Journal

mrjaw14

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Joined: May 22,

Messages: 1,947

Location: Nashville, TN

Aug 3,

I've recently got into welding and am getting supplies. never used a flap disc before. Used plenty of grinding, cutting, and wire wheels. I'm curious what grit if flap disc is used most often in welding, and which brand(s) you guys like, where to buy etc. I've heard good things about Walter flap discs, the ones you can trim the backing and get more life out of. What say ye about flap discs? To avoid these ads, REGISTER NOW!

FakeNewsRealHP

Well-known member

Joined: Oct 27,

Messages: 83

Location: Midwest

Aug 3,

40grit to removed welds, 120 to finish a surface. The Walters are pretty awesome and i use 4.5” or 5” on a metabo. ABN 2” discs off amazon are nice for the coin but I’m spoiled and all consumables from work are free and we get 3M Cubitron for flaps and cutoff wheels.

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sqznby

Well-known member

Joined: Oct 26,

Messages: 969

Location: Coastal NC

Aug 3,

I prefer a flapper over a hard wheel. The noise reduction alone is worth it.

Its always good to have a few on hand.

Grinding, blending, deburring, chamfering, material removal, spatter removal etc,,,,,,, They even have a corner wheels for grinding out/down welds.

Walter makes great products. There's plenty to choose from.
3M, Norton, Benchmark Abrasives, DeWalt, Metabo the list goes on and on.

Give Benchmark a try, they have great prices and usually sell in bulk for far less than most stores. Start with a 40 grit. After its worn in some it'll be more like an 60, 80 or 120 depending on how hard you are with it.

Bigblue&Goldie

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Joined: Mar 12,

Messages: 10,285

Location: AZ

Aug 3,

I buy Benchmark in bulk. They are cheap and seem to work well enough.

Natemade

Well-known member

Joined: Dec 22,

Messages: 66

Aug 3,

Yeah...flap wheels over grinding wheels for pretty much every thing. I keep 40grit and 80grit in the shop all the time. I use Roark supply, they have good prices and hi quality wheels. I have not tried the ceramic ones yet but even if they work half as good as ceramic belts on the belt sanders they will be awesome.

TTMotorsports

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Joined: Jan 8,

Messages: 1,107

Location: Lucerne Valley, CA

Aug 3,

I've been using benchmark jumbo flap discs for years. Buy 100 or so at a time. 40 grit here.

dr_clyde

Well-known member

Joined: Jan 7,

Messages: 6,160

Location: Holland, MI

Aug 3,

Flap discs are for people who haven't discovered resin fiber discs.

Seriously, I don't understand why everyone uses flap discs when resin fiber discs exist.

A fraction of the cost, and are way, way more long lived. I buy VSM ceramic 36 grit and 80 grit discs, and they are the best I've found. 36 grit moves some metal fast, and 80 grit blends a little finer for the next set of abrasives. I use 5" on a 4.5" backer pad.

They are less than $1.50 on amazon. I get them for about a buck a pop from my welding supply. They outlast a flap disc by about double.

I run a professional welding shop, and we might use one or two flap discs a year. I can't remember the last time I bought some. The are ok for blending and the occasional corner blend, but for general grinding, fiber discs all the way.

American Locomotive

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Joined: Jan 8,

Messages: 10,404

Location: Rhode Island

Aug 3,

The resin fiber discs are okay for certain tasks, but I prefer flap discs for others. There's a lot of overlap between hard grinding wheels, flexible grinding wheels, flap discs and flat resin fiber discs, but they all have areas they excel in compared to others.

For the stuff I do, I like using the flexible grinding discs to remove material, and then blend and clean with flap disc.

KBigg

Well-known member

Joined: Apr 15,

Messages: 474

Location: NE Indiana

Aug 3,

Ive never seen a resin fiber disc at my local hardware so i use flap discs. They're nice for removing scale and surface rust quickly as well without actually cutting into the material.

Edit: Nevermind i have seen resin fiber discs, i just didnt know thats what they were called or how they worked. Last edited: Aug 3,

mike

Well-known member

Joined: Oct 17,

Messages: 56

Location: Beautiful Hudson Valley NY

Aug 3,

Flappers are awesome. Great for prepping metal for welds. Most brands last long and with 40 grit you take metal down as fast as a grind disk

TTMotorsports

Well-known member

Joined: Jan 8,

Messages: 1,107

Location: Lucerne Valley, CA

Aug 3,

I use flap disc to cope tubing and stuff like that. I've used resin but if you catch an edge with those they blow apart.

shoot summ

Well-known member

Joined: Jun 8,

Messages: 2,875

Aug 4,

I buy Benchmark in bulk. They are cheap and seem to work well enough.

This, great company, and great products.

slodat

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Joined: Feb 6,

Messages: 3,616

Location: Central-ish, WA

Aug 4,

Thanks for the recommendations! I ordered a few things mentioned in this thread. I have a new variable speed Metabo 5" grinder coming, too

rvieceli

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Joined: Nov 3,

Messages: 748

Location: Illinois

Aug 4,

Dr Clyde what backer pad do you use for the fiber discs? i can't seem to find one that I like.

Thanks

tarbellb

Well-known member

Joined: Apr 17,

Messages: 5,237

Location: Oregon

Aug 4,

Flap discs are for people who haven't discovered resin fiber discs.

Seriously, I don't understand why everyone uses flap discs when resin fiber discs exist.

A fraction of the cost, .......

This ^^^

I jumped on the flap disc a while back, and they are great, but also expensive, especially if you dont know how to dress them.

I now mostly run fiber disc. My experience is that fiber disc give you a more consistent removal rate over the life of the abrasive. Where as a flapper has stages of removal.

btw Benchmark is your typical cheap Chinese stuff, not bad, but def not great. My favorites are: Walter, Pferd, 3M, SAIT, United Abrasive, Weiler, Mercer, Metabo, Norton.

dr_clyde

Well-known member

Joined: Jan 7,

Messages: 6,160

Location: Holland, MI

Aug 4,

Dr Clyde what backer pad do you use for the fiber discs? i can't seem to find one that I like.

Thanks

I use one from Milwaukee. Cheap and lasts about 100 discs or so before I damage it or something.

Marctrees

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Joined: Mar 5,

Messages: 6,265

Location: TX/LA border - Toledo Bend

Aug 4,

drClyde suggested "Resin fiber discs"

Can someone link to an example clearly showing exactly what they are / look like ?

Marc

Wanna Ride

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Joined: Jul 28,

Messages: 2,790

Aug 4,

I buy Benchmark in bulk. They are cheap and seem to work well enough.

Same here, got an online coupon a while back for something crazy like, 10 for $10. Well worth it and I’ll always buy from them now.

slodat

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Joined: Feb 6,

Messages: 3,616

Location: Central-ish, WA

Aug 5,

drClyde suggested "Resin fiber discs"

Can someone link to an example clearly showing exactly what they are / look like ?

Marc

These are the ones he mentioned.

https://www.amazon.com/dp/B072JGMCQJ/?tag=atomicindus08-20

slodat

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Joined: Feb 6,

Messages: 3,616

Location: Central-ish, WA

Aug 5,

I jumped on the flap disc a while back, and they are great, but also expensive, especially if you dont know how to dress them.

How do you dress them? To avoid these ads, REGISTER NOW!

Marctrees

Well-known member

Joined: Mar 5,

Messages: 6,265

Location: TX/LA border - Toledo Bend

Aug 5,

slodat - OK, yup I use that type.

Thank you, Marc

74cj5

Member

Joined: May 3,

Messages: 18

Location: Omaha, Ne

Aug 5,

Haven’t tried those, are they similar to the smaller ones for the air grinders?

Kaizen

Well-known member

Joined: Jan 9,

Messages: 6,868

Location: New England

Aug 5,

How do you dress them?

Curious as well. I had seen something about running it on a sharp edge like a welding table renews it but unsure if it’s true?

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red94chev

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Joined: Jan 29,

Messages: 556

Location: Northeastern MD

sberry

Banned

Joined: Jun 18,

Messages: 35,747

Location: Brethren, Michigan

Aug 5,

I am going to order some of the resin doc talks of. I got a flap or 2 I bought for field work, never used one. I am an absolute master of the 1/4 hardwheel, so used to it that I can do 95% of it with that and even some sanding as it coasts down.
I am going to get some 7 inch resins though, should get a pack as I put on my last 6 the other day. I have a 5 inch, I should turn the air down some when I use it but can cut a worn 7 down with old snips to use it on 5 but I don't like it as well as the bigger one.

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rattle_snake

Well-known member

Joined: Jun 25,

Messages: 4,731

Location: Chandler, AZ

Aug 5,

Flap discs are great for some jobs but not all as already said. I have a grinders set up with flaps, fibers and abrasives so I can use whatever works best without changing wheels.

or at least it is a good excuse for another tool.

tarbellb

Well-known member

Joined: Apr 17,

Messages: 5,237

Location: Oregon

Aug 5,

Curious as well. I had seen something about running it on a sharp edge like a welding table renews it but unsure if it’s ok

Essentially. When the outside edge gets gummed up or slick you cut it down. I do this by finding a sharp edge, sheet metal, etc... And cut it back till you see new fresh abrasive. Some are made for it, Walter, SAIT, have a poly backing, but all can be dressed.

sberry

Banned

Joined: Jun 18,

Messages: 35,747

Location: Brethren, Michigan

Aug 6,

My basic and number 1 is electric 1/4x 4 1/2. I have most of the specialty items on air. Electric and hard wheels are so much cheaper to operate and use light cord. It saves a lot on air comp, I use them quite a bit.
If I didn't have the air would probably use flaps. Last edited: Aug 6,

jeepinerdeep

Well-known member

Joined: Dec 28,

Messages: 2,098

Location: South Central PA

Aug 7,

I use the 40 grit high density Benchmarks. Great performance for the cost. Easy buy on Amazon.

I have run exactly 4 resin fiber discs and the all blew apart. Threw the box and backer in the trash before someone got hurt. Seems like 's technology to me.

dr_clyde

Well-known member

Joined: Jan 7,

Messages: 6,160

Location: Holland, MI

Aug 7,

I use the 40 grit high density Benchmarks. Great performance for the cost. Easy buy on Amazon.

I have run exactly 4 resin fiber discs and the all blew apart. Threw the box and backer in the trash before someone got hurt. Seems like 's technology to me.

You must have had some real shit ones, because I literally have run hundreds and hundreds with no problems.

Marctrees

Well-known member

Joined: Mar 5,

Messages: 6,265

Location: TX/LA border - Toledo Bend

Aug 7,

I use the 40 grit high density Benchmarks. Great performance for the cost. Easy buy on Amazon.

I have run exactly 4 resin fiber discs and the all blew apart. Threw the box and backer in the trash before someone got hurt. Seems like 's technology to me.

Now I am confused.

Will someone clarify exactly what product is being talked about in the above two apparently opposite paragraphs ????????

And link to the recommended SPECIFIC ? "Benchmark" ? product(s) on Amazon please ?

Marc

slodat

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Joined: Feb 6,

Messages: 3,616

Location: Central-ish, WA

Aug 7,

https://www.amazon.com/Premium-High-Density-Jumbo-Zirconia

I searched for "benchmark flap disc 40 high" on Amazon. They were the first result. Same with the others.

The resin fiber discs are in the previous post where I answered your question about them.

jeepinerdeep

Well-known member

Joined: Dec 28,

Messages: 2,098

Location: South Central PA

Aug 7,

You must have had some real shit ones, because I literally have run hundreds and hundreds with no problems.

I had these, just hated them for my application. If I were deburring the outside corner of plate all day they would have worked. Anything with an edge or inside corner meant immediate destruction. Life is too short for that.

https://www.amazon.com/gp/product/B00C0LT8UU/?tag=atomicindus08-20

Now I am confused.

Will someone clarify exactly what product is being talked about in the above two apparently opposite paragraphs ????????

And link to the recommended SPECIFIC ? "Benchmark" ? product(s) on Amazon please ?

Marc

Easy now. Benchmark ( El Cheapo ) Discs are all over Amazon

https://www.amazon.com/gp/product/B01D0HA3LK/?tag=atomicindus08-20

Marctrees

Well-known member

Joined: Mar 5,

Messages: 6,265

Location: TX/LA border - Toledo Bend

Aug 7,

The thing is it is often unclear in posts above if someone is talking about flap or non flap resin at that moment.

Example right below - Only your link showed me if it was a flap DISK or a resin DISC to be used w backer.

Thank you.

Marc

slodat

ALLIANCE MEMBER

Joined: Feb 6,

Messages: 3,616

Location: Central-ish, WA

Aug 7,

Marc, I linked to two specific products. The first was the resin disc dr_clyde mentioned. The second the flap disc jeepinerdeep mentioned..

xjfish

Well-known member

Joined: Feb 22,

Messages: 1,184

Aug 7,

Interesting thread. I switched to (and prefer) conventional flap-disks for mower blade sharpening and dirty metal cleanup. I've always used cheap conventional grinder discs for weld clean up... I'm NOT a pro welder

BryceW

Active member

Joined: Sep 21,

Messages: 37

Location: Columbia, SC

Aug 7,

I'll be the tenth person to recommend Benchmark abrasives. Are they the best/longest lasting? No. They are however quite good and the best I've been able to find at a reasonable price. As far as grit I use 40 for dressing welds and rough blending and 120 if I need to put a finer finish on something or work an edge. I go through about 3 times as many 40s as 120s. I can't remember the last time I used a traditional grinding disc. I get about the same rate of removal from a 40 grit flap disc with half the noise and vibration.

dr_clyde

Well-known member

Joined: Jan 7,

Messages: 6,160

Location: Holland, MI

Aug 8,

I will say the resin fiber disc isn’t intended to grind inside corners or fillets. I can see how it would be poor at that.

I do primarily flat and OD work. Seams and corners and such.

Grooves and fillets tend to be ground out with a hard 6” pipeline stringer disc.

Flap discs have their place, don’t get me wrong, but for a general grinding wheel, they’re very expensive and don’t last very long compared to a hard disc or a resin fiber disc.

sberry

Banned

Joined: Jun 18,

Messages: 35,747

Location: Brethren, Michigan

Aug 8,

I got to clean a little rust from used steel where welds go and square cuts some, 95% hard disc and mostly fillet welds that never get ground. Some spatter cleaning and I can sand quite well with a hard disk. I weld a little flat on the bench mostly vertical on equipment with some overhead which is really my favorite most of the time.

How to Select the Right Flap Disc - Products Finishing

Over the last decade, flap discs have been the fastest growing abrasives category in metal fabrication. From a product performance standpoint, they offer fast stock removal and provide grinding, blending and finishing with one product, for a lower total cost. Flap discs also feature cooler cutting with less gouging and burning.

You can find more information on our web, so please take a look.

From an operator’s viewpoint, flap discs are preferred for several reasons. The discs are lighter weight, easier-to-control and require less downtime for product changes. Operators also favor the reduced vibration and resulting fatigue, as well as reduced noise that they offer.

With all the benefits afforded by flap discs, it is important to know how to select the right one by understanding all the variables and how they apply to your metal fabricating application.

Flap Disc Shape

Because flap discs are used almost exclusively on right-angle grinders, they are designed with a hub that enables work to be done on the face (flaps). The flaps can be applied to the work at an angle or flat. The shape of the flap disc, whether conical (Type 29) or flat (Type 27), provides different performance features, as illustrated in Figure 1.

Figure 1

Flap Disc Backing Plate Material

The second major question to address when selecting a flap disc is what type of backing plate you should use (Figure 2). All flap discs are a combination of abrasive flaps adhered to a rigid backing plate. It is the backing plate that provides stability during operation, and they are available in three different material types:

Fiberglass backing plates help to absorb vibration and are consumed during use with no smearing. Fiberglass is the most popular material because of its high strength and light weight.

Plastic backing plates are becoming more popular due to their conformability as well as the fact that they are trimmable, which allows more use of the flaps, especially for blending and finishing. (To view a video on how to trim plastic backing plates, visit hpmvideo.saint-gobain.com/wsi-ab- sga-na/video/trimmable_backing.mpg.)

Aluminum backing plates are the least- popular but are well-suited for applications that demand extra-high strength and rigid support. While not consumable during use, an aluminum plate can be recycled.

You will get efficient and thoughtful service from PTATOOLS.

Abrasive Flap Densities

The quantity, angle and spacing of the flaps on the backing plate can vary substantially. This is referred to as the density of the flaps. It is important to match the flap density with your application, if possible, to achieve the best results (see Figure 3).

Abrasive Grit

Probably the most important criteria are the type of abrasive on the flap and the appropriate grit size. For metalworking, there are three primary abrasive types:

Ceramic alumina—The latest innovation in abrasives, this grain micro-fractures to enable a continuous supply of the sharpest cutting edges. This provides the fastest cut as well as the best utilization of the entire grain for the longest life, especially on stainless or high-alloy materials

Zirconia alumina—This is an excellent blend of zirconia and aluminum oxide grain that provides a very good cut rate-to-cost ratio. This is a very good choice for carbon/mild steel applications.

Aluminum oxide—The original metalworking abrasive, this product is recommended for smaller jobs where a consistent, low-cost product is needed.

Grit Size

Grit size is the final component you need to select to match your application. The grit recommendation chart (Figure 4) can assist in selecting how coarse or fine you should go.

Flap discs are a versatile solution for most metal fabrication applications. Understanding the five variables outlined here will help you pick the correct one.

Most manufacturers offer a broad stock line of 4 to 7 inches to fit all popular right-angle grinders. Some also offer custom manufacturing of flap discs to meet specialized or high-production applications. Your sales representative should be able to help you understand the total line available to you and provide you with the best grinding, blending and finishing solution for your metal fabrication application.

For more information, please visit Flap Discs Manufacturer.

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