Grinding disk vs flap disk?

[skotl]

I've got three angle grinders set up - one with a cutting disk, one with a grinder and one with a flap disk.

I pretty much just use the cutting and the grinding set ups (and can definitely recommend having two grinders rather than having to swap disks every three minutes) but used a new flap disk today for the first time in ages.
It was like a hot knife through butter and made me wonder: What would you use a grinding disk for rather than a flap disk? The flap seems so much faster and neater.

 

[Parm]

I quite agree. The flap discs are quite awesome

 

[Robotstar5]

Maybe it's cost?, grinding wheels can be run down to a nub flapdisks wear quite quick which is fine if they're available from the company stores

 

[pedrobedro]

I stopped using flap discs when I got a backing pad and fibre discs.

 

[Paul.]

Grinding discs are used for quick stock removal, they are cheaper, last longer and cut quicker than a flap disc, but will give a coarser finish.
If you have tall welds to get rid off then use a grinder as a first cutting tool prior to finishing with a flap or fibre disc, a pet hate of mine is rough grinding disc swirls on a supposedly finished job.
I suppose for a diy'er doing the odd small job the cost difference is not too apparent, but in a shop with a fair bit of finishing going on you can soon rip through a pack of flap disks,

 

[Hood]

I only ever use flap discs nowadays. They are much more expensive but are much more controllable and much quicker , you can use them for light touches or heavy removal.
The ones I use are from Wurth, the ceramic ones, and although about double the price of others they last probably 4 times as long and continue cutting right to the end where others lose their abrasiveness when halfway used.

Most of my work is stainless or Alu but they work just as well on steel.

These are the type I use.

 

[gaz1]

Grinding discs are used for quick stock removal, they are cheaper, last longer and cut quicker than a flap disc, but will give a coarser finish.
If you have tall welds to get rid off then use a grinder as a first cutting tool prior to finishing with a flap or fibre disc, a pet hate of mine is rough grinding disc swirls on a supposedly finished job.
I suppose for a diy'er doing the odd small job the cost difference is not too apparent, but in a shop with a fair bit of finishing going on you can soon rip through a pack of flap disks,

i have both discs and use them as paul quotes

i also find the flap disc is also best for quick clean up of new metal get it near rusted metal or painted metal it blocks easily a quick run at the side usually cleans it off again

i have 40 grit 60 grit and 80 grit flap discs the finish is loverly when polished up

 

[Rocketman]

The trouble with flap discs is the bowling out of material of each side of the weld. This can be a real problem on thin metal. I always hit first with a grinding wheel because you can remove most of the weld first without any thinning of metal next to it. Get it close and finish off with a flap disc evenly.

 

[waddycall]

I hate flap discs. They have a tendency to wrap themselves around welds and into holes, cutting in where you dont want as rocket man said. It’s sanding discs and a backing pad for me every time. I use grinding discs to get close if I need to. With a sanding disc and backing pad you can get a really good finish without any dishing.

 

[cumbriasteve]

I think preference or perhaps inbred use of discs for me comes from my youth, we used to make a lot of stuff for the nuclear industry and for future ease of decontamination a lot of the welds had to be polished out totally.

We had large heavy air grinders and started with a course wheel, to a fine wheel, to a flap wheel and finally a polishing mop, grinding discs were never used and I'm pretty sure flap discs were not around.

So today if I want a weld ground down and polished the final runs are always with a flap wheel of various grades, they are not as fast as a flap disc but I find them easier to control, probably because that's how I was taught.

 

[rcx132]

I noticed the same, that flap discs are faster and generate less heat as well. I bought cheap flap discs and will probably stick to them as the time saved vs price is good.

Going to try the backing pad and sandings discs that people have mentioned.

 

[Windy Miller]

Quick question about the fibre sanding discs that get mentioned so often:

You guys seem to be using a rubber backing pad - I have a white plastic backing pad - nylon maybe? Is this just as good or is rubber the way to go?

 

[pedrobedro]

Quick question about the fibre sanding discs that get mentioned so often:

You guys seem to be using a rubber backing pad - I have a white plastic backing pad - nylon maybe? Is this just as good or is rubber the way to go?

It doesn't matter what it's made of as long as it is flexible. The one I have now is flexible nylon and it has lasted really well.

 

[500e]

Prefer the rubber they don't seem to kill the first 10mm of disk & leave the rest

 

[Spark plug]

Prefer the rubber they don't seem to kill the first 10mm of disk & leave the rest

I’ve always used the white plastic ones, as it’s what the shop sells. Might have to try a rubber one.

IMO for flat work fibre discs trump flap discs any day.

I like SIA blue line fibre discs as my weapon of choice.

 

[Wightsparks]

Never used a fibre sanding disc - I only learned on here a few months back about flap discs which to me are much better than a grinder for finishing. But at £5 for a rubber backer and a box of discs I'm off to Toolstation to try it out.
My garage would have a lot more space in it if it wasn't for you lot!

 

[Tiggy_dorset]

I very rarely use a grinding disc. Flap discs are awsome for stock removal and use on unusual shapes and radii. I would do most work with a flap but always use the sanding discs on a backing pad for the final finishing of flats.

Sanding discs I always use a rubber backing pad. You need the flexibility and helps to get more life out of your discs. The nylon pads I find are way too rigid.

sanding discs: the brown aluminium oxide discs don't last 5 minutes. The blue zircon discs last a bit longer but still have nothing on the green ceramic discs. The green discs are more expensive but makes so much more economic sense. I will always go for green given the choice.

 

[PhillipM]

I generally only keep a couple of grinding discs in....and a some packs of 100 flap discs, so that should tell you my preference. However, if you need a square edge, or to reach in end on somewhere tight...that's when the grinding discs come out.

 

[zeppelin builder]

I only ever use flap discs nowadays. They are much more expensive but are much more controllable and much quicker , you can use them for light touches or heavy removal.
The ones I use are from Wurth, the ceramic ones, and although about double the price of others they last probably 4 times as long and continue cutting right to the end where others lose their abrasiveness when halfway used.

Most of my work is stainless or Alu but they work just as well on steel.

These are the type I use.View attachment 124696

The best tool for prepping chamfers on ali is a surform file if its new it just rips the metal off and no heaps of ali dust to give you àlzheimers
Oh i" forgot 'we we all brought up with alu pots

 

[Hood]

The best tool for prepping chamfers on ali is a surform file if its new it just rips the metal off and no heaps of ali dust to give you àlzheimers
Oh i" forgot 'we we all brought up with alu pots

Have one of these somewhere, just forgotten where
Would they work on the harder Mag Alloys? Not that I chamfer much as most stuff is thinnish so full pen is easy, sometimes too easy