Why is efficient metal grinding disc Better?

For hard materials a stone will remove material faster. Softer, especially non ferrous materials a coarse flap disk will take the lead.

That is what everyone says, but there doesn't seem to be evidence from the manufacturers to support that.

https://www.youtube.com/watch?t=194&v=svB1iq4yRCE
Skip to 2:50 to see a side by side of a flap disc, grinding disc, and sanding disc. The flap disc easily and clearly outpaces the grinding disc grinding down steel.

http://www.homedepot.com/p/Diablo-4...ype-29-Conical-Design-DCXN01F/
Both the videos there also show the same thing, the flap disc is faster on steel.

In addition, many manufacturers of flap discs actually recommend (ceramic) flap discs over grinding discs for stainless steel, titanium, and other hard alloys.

If time is worth more than money, then flap discs may work better in a lot of situations. If money is worth more than time, then the grinding discs will work fine.

So it does just come down to time vs money and which do I have more of then...With Lehigh Valley flap discs only be $2 each (and they last a long time, even under heavy use), I suppose that increase in cost ($0.80 per unit) is probably worth it then. For a small time fabricator, the flap discs will probably give me great life.

I just find it odd that there is such a difference on opinion on which one is faster. Before today (when I saw those videos), I'd always assumed grinding discs were way faster (and hence only bought grinding discs because I don't care about having a smooth/glossy finish on most of what I am welding).

https://www.youtube.com/watch?t=194&v=svB1iq4yRCE
Skip to 2:50 to see a side by side of a flap disc, grinding disc, and sanding disc. The flap disc easily and clearly outpaces the grinding disc grinding down steel.

This video isn't that equal. Look at frames 2:59 - 3:00. At the 1/2 frame 2:59:15 (1/2 way between the 2 frames) you can see each weld by itself before the grinders block the view. The centre weld is way more uniform and it looks like it sits lower too but it's hard to tell. For sure the 2 outside welds have more high bumps to grind down. They should have used one continuous 12" weld and cut it into 3 pieces each 4" long, then done the comparison. It would also be easy to use crappy grinders against one good one. Not saying they did but...

julianf

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8,419

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devon, uk

• May 24,

• #1

I've never really had much power out of grinding discs, and I fear I'm missing somthing?

When would you use a grinding disc over a flap disc?

Thank you.

Gareth

You'll need 16 pigs to do the job in one sitting!

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1,559

Location

Norwich, Norfolk, UK

• May 24,

• #2

For pre weld clean up and prep work including veeing on stuff up to 12mm thick I get on really well with 115mm X P36 Zirconium (Blue) sanding discs.
I get 8-10 minutes actual work life out of each disc which is a comparable to grinding disc work-lifespan.
However, on a cost per unit/lifespan basis I have found them to be considerably more economical than similar grade flap discs.

Munkul

Jack of some trades, Master of none

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7,670

Location

Cumbria

• May 24,

• #3

I've never really had much power out of grinding discs, and I fear I'm missing somthing?

When would you use a grinding disc over a flap disc?

Thank you.

When you want to work the edge of the disc and not the flat, grinding discs are better. They also don't clog up as easily with rust and crap. They don't deflect, so you can dig into stuff harder.
They have their place... not as enjoyable to use as flap discs due to the NVH, but sometimes a far better choice than flap discs.

Blobber

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lincolnshire

• May 24,

• #4

I find with body work grinding discs are good to get the top off the weld and then finish off with a flap disc, the hard discs dont put as much heat into the panels

fizzy

Member

Messages

13,063

• May 24,

• #5

I seem to always use flap disks these days. Much safer and just as fast.
In fact I use my Black and Decker power file even more. Love it. I use the blue 40 grit belts - last much better and never break.

eddie49

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4,520

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Reading, Berkshire

• May 24,

• #6

I use the blue 40 grit belts - last much better and never break.

Do you have a link to a supplier? ( Sorry for thread hijack.)

Richiew

Forum Supporter

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2,956

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Teesside, England

• May 24,

• #7

I use grinding discs very rarely now. Maybe my welding is improving?

Perhaps I am just less fussy these days...

MetalMonkey

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3,084

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UK

• May 24,

• #8

How about fibre discs?
I find them better than either flap discs or stones for removing stock or welds in a hurry.

Memmeddu

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5,141

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Italia Sardegna

• May 24,

• #9

I do prefer flap discs over grinding discs
Because they're more pleasant to use cause less vibrations.
However grinding discs are cheaper and last longer for heavy metal removal .
But ceramic based flap discs eat much more than grinding ones with all the advantages and disadvantages of flap discs

Memmeddu

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5,141

Location

Italia Sardegna

• May 24,

• #10

How about fibre discs?
I find them better than either flap discs or stones for removing stock or welds in a hurry.

What do you mean?
For fibre discs I mean "scotch brite" ones
Which sure have their place but don't last long

mtt.tr

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Essex/Suffolk border

• May 24,

• #11

I use grinding discs for grinding and flap discs for cleaning or finishing.

Horses for courses

PhillipM

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3,035

• May 24,

• #12

Flap discs are generally much faster anything than grinding discs tbfh. But, when you want to work the edge of the disc into a corner, a grinding disc is what you want.

anto44

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1,846

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ireland

• May 24,

• #13

Grinding discs are better than flap discs for grinding out fillet welds right into the root, flap discs always leave a big radius in the corner

tigdlo

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1,021

Location

UK

• May 24,

• #14

Really depends what you are doing, out of all the abrasives I have, zirconia flap discs get used the least. Currently I use 6mm grinding disc for control and working on the edge of the disc into a corner for example, ceramic/zirconia flat sanding discs/fibre discs for general cleaning and a 36g Cubitron for rapid material removal. For final finishing norton blaze strip/clean discs are very good, blends the flat spots from sanding very well.

hermetic

Member

Messages

484

• May 24,

• #15

There are grinding discs, and then there are grinding discs! I like flap wheels too, but they don't last very long, although they do last better if you are working on paint and rust free metal, great for paint removal, but dont last long! As for grinding discs I have found that the Lidl ones last really well, but seem to cut really badly unless you sit on them, wheras the softer ones remove more metal, faster, but have a short life!

brightspark

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yarm stockton on tees

• May 24,

• #16

grinding disks are what it says for grinding . fast metal remover / flap disks are just rotary emerycloth for light metal removal and sanding

grim_d

Unlikeable idiot.

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4,267

Location

Scotland - Ayrshire

• May 24,

• #17

I don't use many grinding discs these days unless I need to remove a lot of material...and simply because they are cheap.

40grit flap for stock removal, 80grit flap for roughing in, 100grit fibre disc for smoothing out...then the real game changer is a unified blending disc like Norton rapid blend for final blending.

Not a great photo but trust me those discs are the mutts!

Shedendman

Member

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5,425

• May 24,

• #18

Depends on the weld you've done,if neat and ok,maybe a tidy up with a flap,but if you've made a total hash of your joint,to which it looks like your granny would have done better blind drunk,etc(and dont say we've not )
then smash the 6mm in and go over it again
I read somewhere just because you're good at grinding,it dont make you a good welder

Turbo

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6,809

Location

Fermanagh, Northern Ireland

• May 24,

• #19

I find grinding discs are still the best for rapid metal removal. I recently bought some Lidl next generation discs & they are scarily good at grinding down welds with less dust & sparks.
The ceramic flap discs do come close to grinding discs & leave a nicer finish but they are relatively expensive & they are easy to overheat by working them too hard.

Something I use a grinding disc disc for is when I've forgot to bevel stuff before tacking it up. I run the grinding disc along the joint cutting a 6mm groove which serves as a bevel to get good penetration on thick steel.