Flap discs - what's the secret?

[Highpower]

So what is the secret to using a new flap disc for more than 5 minutes?

I put a brand new 36 grit flap disc on my angle grinder to clean the mill scale off of some angle iron. The disc cut like a house of fire on the first piece of angle, peeling off the mill scale like a hot knife through butter.  

Half way through the second piece of angle, I had to lean into the grinder to keep it cutting. The abrasive is gone from roughly 1/4" of the outer ends of the flaps and it just rubs on the backing material. All it does is polish now rather than cut.  

So how do you keep these things working, and not waste 2/3 of the disc that still has abrasive trapped below? What do you have to do.... STAND on the grinder?  

[Mayhem]

Try a shallower angle of attack.

[f350ca]

Try pushing it into a sharp edge like the cut on the end of the angle iron, it might just be plugged up with rust.
I use them all the time to blend welds and general cleaning as your doing, but really heavy rust gets the 24 grit on the 7 inch angle sander.

[ieezitin]

Best of luck. 

I know this much... getting rid of millscale will abuse the hell out of a new disk, take that off with a 1/4'' thick grinding disk then change over to the flapper. They dont last long but when you get down by lets say a quarter run the edge of the disk on a piece of flat steel to grind off the edges and start over, dont buy cheap brands you get what you pay for.

Saying all that they are really great if you dont have to pay for them, i am an ex pipe welder they made my life a breeze on prepping my butt joints and skimming my cap edges..... they allso make different pads for different materials.

Anthony..

[f350ca]

Some are red oxide colour and some blue, which is for what?

[Highpower]

These are the discs I have.  Camel Grinding Wheels
My attack angle was approx 5 - 10°.
There was only light surface rust on one half of 1 piece of angle (out of 3 pieces - 19" long). There is no build up of any kind on the disc.
IIRC, these were $7-$8 each when I bought them so they aren't cheap...

Quote:UPC #: 42301
Name: Z3 Regular Disc
Application: Active grinding agent provides cool cutting with light pressure. Special optimized resin bond offers maximum cutting capacity, strong edge stability and long life.
Description: Premium Zirconia Alumina grain with a poly/cotton heat treated backing. The poly/cotton combination provides low stretch and strength for the high Zirconia concentration that Z3 contains. Fastest grain removal in the marketplace for carbon based steels (26% more than the competition) and second best after CGW Z-Stainless discs on stainless steels, while offering excellent life.
Comments: Contaminate-free. For working on flat grinding surfaces. Most efficient when used between 0°–15° angle. The best choice for smooth finishing.
Suitable For: Recommended for aggressive use and heavy duty applications.
Diameter: 4 1/2?
Arbor Hole Size: 7/8?
Thickness: Regular
Grit: 36 (Medium)
Type: 27 – Depressed center flat disc
Use: Right angle grinder
Max Operating Speed: 13,300 RPM
Material: Zirconia
Made In: USA
Quantity: 10

[trevatxtal]

(10-13-2015, 04:26 PM)Highpower Wrote: So what is the secret to using a new flap disc for more than 5 minutes?

LIGHT pressure only.
The abrasive is stuck to a canvas or cloth pad, pressure rips it off.
Flap disc are for finish not rough cut.
Always prep with a grinder disk.
Authority= many hundreds used over many years on Stainless steel, mild steel, hardened steel, wood and plastics.
Works for me.
Trev

[Highpower]

Anthony, I don't have the "trimmable" discs  - just the regular ones with the fiberglass backing.  





Trev, I hear where you are coming from. I guess what I am NOT understanding is why the cloth backing strips don't just wear down and expose more new abrasive that is still sitting between the stacked layers of strips? The strips are 3/4" wide but the disc just stopped working after the 1/4" of strip that was exposed had worn out. So now it just rubs on the bare ends of the strips without cutting. Isn't the idea to have the entire strip wear away and not just the abrasive?  

[trevatxtal]

Highpower I do see your point.
I have never had that problem.
In the next few day I will try to over work a pad and see what I come up with.
The way I have used them I end up ending with next to nothing or one or more of the flaps fall off.
Hope fully we will come up with an answer.
Trev

[Highpower]

I ordered a few more discs of different brands and types to try. Some have fewer strips spaced farther apart. Some have MORE strips spaced closer together and are thicker. The CGW "XL" is supposed to be Xtended Life(?) but I have a sneaking suspicion it will stop cutting even sooner than the "regular" disc I'm having the problem with.  

   

This is the regular CGW disc that quit cutting on me. It only rubs on the bare ends of the cloth backing now. Lots of abrasive still trapped between the layers but if you can't get it to contact the material you are trying to grind/sand on.....