Getting More First Minutes Out of A Flap Disc

[Bob La Londe]

Yesterday I found myself cleaning up a bit of square tube in preparation
for welding and later paint. It was outside, but in SW Arizona, that
just means it has developed a small amount of protective rust over the
mill scale.

I started with an angle grinder and a flap disc. It made short work of
the light loose rust, but would hardly touch the mill scale. It also
showed some rust down "in the" the mill scale. I probably could have
stopped there, but I got carried away with myself. This stuff welds
really nice if you have bright shiny metal and takes a good paint coat
as well with an etching primer, and proper cure times.

I probably I could have just used extend or some other rust neutralizing
primer after knocking off the loose rust, but this construct will be
going into a humid environment.

I noticed a fresh flap disc stripped rust, and mill scale amazingly
fast. It did more work with less effort in the first minute or two than
it did in the next ten. Now the flap disc was still nearly new, but it
was performing like one that was half worn away. There was still plenty
of grit, but the edge was mostly the flaps rather than the grit, and the
face was the same, but also gummed up with mill scale.

I am NOT trying to get longer life out of a flap disc. I am trying to
get more time performing like the first minute or two of a new disc. I
don't care if the total life of the disc is less. Is there a practical
way to dress these so that you can expose more grit quickly. I tried
spinning it against a wire wheel on a bench grinder. The result was
less than amazing.

Sans the solution I am looking for is there a better disc for stripping
metal than an abbrasive flap disc? I can do the work with a grinding
wheel, but its much more skilled to avoid gouging the base metal and
doing damage. I tend to only use a grinding wheel to make the bevels
before welding.

[David Billington]

Post by Bob La Londe
Yesterday I found myself cleaning up a bit of square tube in
preparation for welding and later paint.  It was outside, but in SW
Arizona, that just means it has developed a small amount of protective
rust over the mill scale.
I started with an angle grinder and a flap disc.  It made short work
of the light loose rust, but would hardly touch the mill scale.  It
also showed some rust down "in the" the mill scale.  I probably could
have stopped there, but I got carried away with myself.  This stuff
welds really nice if you have bright shiny metal and takes a good
paint coat as well with an etching primer, and proper cure times.
I probably I could have just used extend or some other rust
neutralizing primer after knocking off the loose rust, but this
construct will be going into a humid environment.
I noticed a fresh flap disc stripped rust, and mill scale amazingly
fast.  It did more work with less effort in the first minute or two
than it did in the next ten.  Now the flap disc was still nearly new,
but it was performing like one that was half worn away.  There was
still plenty of grit, but the edge was mostly the flaps rather than
the grit, and the face was the same, but also gummed up with mill scale.
I am NOT trying to get longer life out of a flap disc.  I am trying to
get more time performing like the first minute or two of a new disc. 
I don't care if the total life of the disc is less. Is there a
practical way to dress these so that you can expose more grit
quickly.  I tried spinning it against a wire wheel on a bench
grinder.  The result was less than amazing.
Sans the solution I am looking for is there a better disc for
stripping metal than an abbrasive flap disc?  I can do the work with a
grinding wheel, but its much more skilled to avoid gouging the base
metal and doing damage.  I tend to only use a grinding wheel to make
the bevels before welding.

I know what you're experiencing with flap discs and have used this type
of disc to good effect
https://www.weldequip.com/cleaning-fleece-115mm.htm . I've seen many of
this type for sale on ebay and most don't have a high enough speed
rating for use on a 4.5" grinder so check what you get if you try one.

[Jim Wilkins]

"David Billington" wrote in message news:t5gnp1$71v$***@dont-email.me...

I know what you're experiencing with flap discs and have used this type
of disc to good effect
https://www.weldequip.com/cleaning-fleece-115mm.htm . I've seen many of
this type for sale on ebay and most don't have a high enough speed
rating for use on a 4.5" grinder so check what you get if you try one.

-----------------------

Good stuff, though to me they are over-priced and too short-lived, perhaps
from being sheared down by rust-through holes they uncovered. I don't get
10-20 year paint durability on auto body work unless I sand-blast, which
also cleans out the rust pits better than they do.

[Clifford Heath]

I
don't get 10-20 year paint durability on auto body work unless I
sand-blast, which also cleans out the rust pits better than they do.

Except it doesn't. You need chemical treatment as well, as I'm sure you
know. Metal is crystalline, and some rust will always penetrate into
pores finer than any blasting sand.

Clifford Heath.

[Mike Spencer]

Post by David Billington
I know what you're experiencing with flap discs and have used this type
of disc to good effect
https://www.weldequip.com/cleaning-fleece-115mm.htm . I've seen many of
this type for sale on ebay and most don't have a high enough speed
rating for use on a 4.5" grinder so check what you get if you try one.

I've been using these for many years, first noticed when B&D started
selling a consumer version in the 70s, later same product from 3M and
Germany. They're the only thing that will remove mill scale without
gouging the metal.

But I haven't seen them as angle grinder wheels. I use them on a
high-speed end grinder, ones meant for that use. Just the edge of the
wheel hits the metal. Any steel in otherwise forged ornamental work
that is going to be left unworked can be stripped of mill scale
leaving only faint linear striations, no overlapping partial-circualar
grinder marks. Among other things, I've made 16 ga. panels stripped
this way and blued with Oxpho-Blue(tm). Blueing would take poorly/unevenly
if the mill scale were not stripped and angle grinder marks would look
really bad.

You have to have supporting widgets -- collars with spurs -- to hold
them because they -- at least all the ones I've bought -- come without
any hub.

Post by David Billington
Good stuff, though to me they are over-priced and too short-lived,
perhaps from being sheared down by rust-through holes they
uncovered.

Yeah, you do have to be careful to avoid sharp (or any) edges, holes,
protrusions which eat them away very quickly. Where you can do that,
they last pretty well.

Post by David Billington
I don't get 10-20 year paint durability on auto body work unless I
sand-blast, which also cleans out the rust pits better than they do.

I've used bead blasting for forged ornamental work but, where
possible, I prefer phosphoric acid pickle. Probably overkill for
typical structuraal welding work and it does NOT work all that well on
mill scale.

[Jim Wilkins]

Post by David Billington
I don't get 10-20 year paint durability on auto body work unless I
sand-blast, which also cleans out the rust pits better than they do.

I've used bead blasting for forged ornamental work but, where
possible, I prefer phosphoric acid pickle. Probably overkill for
typical structuraal welding work and it does NOT work all that well on
mill scale.

-----------------

20,30,40 years ago I wasn't taking notes and photos of rust repairs. As best
I remember Naval Jelly didn't guarantee a lasting repair, maybe because I
didn't wash it off properly or dry it fast enough. Etching primer didn't
hold up well either. Sandblasting and a wipe with lacquer thinner did, so I
stopped experimenting. It's difficult to separate the effects of the several
variables involved.

The 20+ year old paint job on my truck's pitted rear bumper is only now
starting to deteriorate. SEMS paint appears to last longer than other spray
can paints I've tried, Duplicolor and PPG needed rework after 2-3 years.
Road salt is a serious problem here but driving can become extremely
difficult without it.

[David Billington]

Post by Mike Spencer

Post by David Billington
I know what you're experiencing with flap discs and have used this type
of disc to good effect
https://www.weldequip.com/cleaning-fleece-115mm.htm . I've seen many of
this type for sale on ebay and most don't have a high enough speed
rating for use on a 4.5" grinder so check what you get if you try one.

I've been using these for many years, first noticed when B&D started
selling a consumer version in the 70s, later same product from 3M and
Germany. They're the only thing that will remove mill scale without
gouging the metal.
But I haven't seen them as angle grinder wheels. I use them on a
high-speed end grinder, ones meant for that use. Just the edge of the
wheel hits the metal. Any steel in otherwise forged ornamental work
that is going to be left unworked can be stripped of mill scale
leaving only faint linear striations, no overlapping partial-circualar
grinder marks. Among other things, I've made 16 ga. panels stripped
this way and blued with Oxpho-Blue(tm). Blueing would take poorly/unevenly
if the mill scale were not stripped and angle grinder marks would look
really bad.
You have to have supporting widgets -- collars with spurs -- to hold
them because they -- at least all the ones I've bought -- come without
any hub.

Post by David Billington
Good stuff, though to me they are over-priced and too short-lived,
perhaps from being sheared down by rust-through holes they
uncovered.

Yeah, you do have to be careful to avoid sharp (or any) edges, holes,
protrusions which eat them away very quickly. Where you can do that,
they last pretty well.

Post by David Billington
I don't get 10-20 year paint durability on auto body work unless I
sand-blast, which also cleans out the rust pits better than they do.

I've used bead blasting for forged ornamental work but, where
possible, I prefer phosphoric acid pickle. Probably overkill for
typical structuraal welding work and it does NOT work all that well on
mill scale.

The Osborn Dronco 4.5" (115mm) ones I have use the standard 7/8"
(22.23mm) angle grinder mounting and are rated at 11,000 RPM max so
suitable for use on my 4.5" Bosch grinder. The only minor issue I find
is due to the depth of the fleece when new it makes it harder to get the
pin spanner on the nut but I can live with that. The Dronco part number
is 6700 001 100. None of the other discs of this type I've seen
advertised had a max speed anywhere near 11k RPM so would have been
unsafe in use.

[Jim Wilkins]

"David Billington" wrote in message news:t5j7jn$nn5$***@dont-email.me...

The Osborn Dronco 4.5" (115mm) ones I have use the standard 7/8"
(22.23mm) angle grinder mounting and are rated at 11,000 RPM max so
suitable for use on my 4.5" Bosch grinder. The only minor issue I find
is due to the depth of the fleece when new it makes it harder to get the
pin spanner on the nut but I can live with that. The Dronco part number
is 6700 001 100. None of the other discs of this type I've seen
advertised had a max speed anywhere near 11k RPM so would have been
unsafe in use.

------------------

What I called 2" scouring pads appear to be a denser, fine-textured variant
on fleece abrasive wheels.

[Jim Wilkins]

"Mike Spencer" wrote in message news:***@bogus.nodomain.nowhere...

But I haven't seen them as angle grinder wheels.
-----------

You have to know the right incantation to invoke Internet magic.
"Deburring disc" returns this:
https://www.penntoolco.com/deburring-discs-1/

[Bob La Londe]

Post by David Billington

Post by Bob La Londe
Yesterday I found myself cleaning up a bit of square tube in
preparation for welding and later paint.  It was outside, but in SW
Arizona, that just means it has developed a small amount of protective
rust over the mill scale.
I started with an angle grinder and a flap disc.  It made short work
of the light loose rust, but would hardly touch the mill scale.  It
also showed some rust down "in the" the mill scale.  I probably could
have stopped there, but I got carried away with myself.  This stuff
welds really nice if you have bright shiny metal and takes a good
paint coat as well with an etching primer, and proper cure times.
I probably I could have just used extend or some other rust
neutralizing primer after knocking off the loose rust, but this
construct will be going into a humid environment.
I noticed a fresh flap disc stripped rust, and mill scale amazingly
fast.  It did more work with less effort in the first minute or two
than it did in the next ten.  Now the flap disc was still nearly new,
but it was performing like one that was half worn away.  There was
still plenty of grit, but the edge was mostly the flaps rather than
the grit, and the face was the same, but also gummed up with mill scale.
I am NOT trying to get longer life out of a flap disc.  I am trying to
get more time performing like the first minute or two of a new disc. I
don't care if the total life of the disc is less. Is there a practical
way to dress these so that you can expose more grit quickly.  I tried
spinning it against a wire wheel on a bench grinder.  The result was
less than amazing.
Sans the solution I am looking for is there a better disc for
stripping metal than an abbrasive flap disc?  I can do the work with a
grinding wheel, but its much more skilled to avoid gouging the base
metal and doing damage.  I tend to only use a grinding wheel to make
the bevels before welding.

I know what you're experiencing with flap discs and have used this type
of disc to good effect
https://www.weldequip.com/cleaning-fleece-115mm.htm . I've seen many of
this type for sale on ebay and most don't have a high enough speed
rating for use on a 4.5" grinder so check what you get if you try one.

I looked at that. I've seen those type of wheels before. How well does
it work on mill scale.

[David Billington]

Post by David Billington

Post by Bob La Londe
Yesterday I found myself cleaning up a bit of square tube in
preparation for welding and later paint.  It was outside, but in SW
Arizona, that just means it has developed a small amount of
protective rust over the mill scale.
I started with an angle grinder and a flap disc.  It made short work
of the light loose rust, but would hardly touch the mill scale.  It
also showed some rust down "in the" the mill scale.  I probably
could have stopped there, but I got carried away with myself.  This
stuff welds really nice if you have bright shiny metal and takes a
good paint coat as well with an etching primer, and proper cure times.
I probably I could have just used extend or some other rust
neutralizing primer after knocking off the loose rust, but this
construct will be going into a humid environment.
I noticed a fresh flap disc stripped rust, and mill scale amazingly
fast.  It did more work with less effort in the first minute or two
than it did in the next ten.  Now the flap disc was still nearly
new, but it was performing like one that was half worn away.  There
was still plenty of grit, but the edge was mostly the flaps rather
than the grit, and the face was the same, but also gummed up with
mill scale.
I am NOT trying to get longer life out of a flap disc.  I am trying
to get more time performing like the first minute or two of a new
disc. I don't care if the total life of the disc is less. Is there a
practical way to dress these so that you can expose more grit
quickly.  I tried spinning it against a wire wheel on a bench
grinder.  The result was less than amazing.
Sans the solution I am looking for is there a better disc for
stripping metal than an abbrasive flap disc?  I can do the work with
a grinding wheel, but its much more skilled to avoid gouging the
base metal and doing damage.  I tend to only use a grinding wheel to
make the bevels before welding.

I know what you're experiencing with flap discs and have used this
type of disc to good effect
https://www.weldequip.com/cleaning-fleece-115mm.htm . I've seen many
of this type for sale on ebay and most don't have a high enough speed
rating for use on a 4.5" grinder so check what you get if you try one.

I looked at that.  I've seen those type of wheels before.  How well
does it work on mill scale.

In my experience they deal with the mill scale on box section I've
cleaned up very well.

[Cydrome Leader]

Post by Bob La Londe
Yesterday I found myself cleaning up a bit of square tube in preparation

[boring crap trimmed]

So OP wants help finding a better type of flap disc, but never mentions
the type they're using now.

[Bob La Londe]

Post by Bob La Londe
Yesterday I found myself cleaning up a bit of square tube in preparation

Snap childish temper tantrum

You know I filtered the sub threads where you went off on your own
little childish temper tantrums, but I didn't filter you entirely. I
figured once you got over your nasty little snit you would start to act
like an adult again. I can see I was wrong. Best of luck to you. I do
honestly hope you grow up someday and eventually have a happy life.

To be clear I do honestly hope at some point you begin to have a happy
life that does not need to be validated by acting nasty and demeaning to
others instead of just being happy with yourself.

[Dirtcrasher]

You must be fun to be around. Is it REALLY that difficult to recommend a good quality disc for the guy?? You need to know what he uses now to offer a suggestion?? Obviously, whatever he is using it isn't lasting very long, so I doubt it's a 3M or SAIT flap wheel..

[Jim Wilkins]

"Bob La Londe" wrote in message news:t5gles$nd7$***@gioia.aioe.org...

Sans the solution I am looking for is there a better disc for stripping
metal than an abbrasive flap disc? I can do the work with a grinding
wheel, but its much more skilled to avoid gouging the base metal and
doing damage. I tend to only use a grinding wheel to make the bevels
before welding.

----------------

I cleaned the paint and rust from the 4" channels for the gantry hoist track
with an HF "2 in. Mini Orbital Air Sander" and a 2" coarse scouring pad, the
only power sander I own that fit flat inside the channels. It was fast
enough on the outside to satisfy my laid-back retiree working rate. After
stripping the four 8' channels it seemed clogged with paint but still cut
well enough to remove the leak-causing corrosion from the rims of the
aluminum motorcycle wheels the sawmill blade runs on. I don't remember if
there was mill scale under the paint on the channels. The pad left shiny
metal.

The HF tool was meant to be double action but it cut faster with the rubber
disk mounted to seat on the outer bearing race and spin instead of
oscillating.

The sander and the 2" and 3" pad kits don't work well together as received.
I made a stub arbor of 1/4-20 threaded rod and used nuts and washers to
control whether the pad spun or oscillated.

It seemed that a 3" pad on a 2" backing conformed to inside curves better
and may have been better on edge for shallow rust pits. Although the used
pallet rack channels had been stored outdoors they weren't pitted enough to
require my needle scaler or sandblaster.

My faster hand held metal flattening tool is a 7" angle grinder with a
saucer wheel. Unlike with the usual disk I can see and feel when it makes
contact around the arc and is cutting flat. I use it where welds will be
bolted together or support something, like the warped engine mount plate on
my second-hand log splitter.

Cleaning square tubing seems like a belt sander task.

[Bob La Londe]

Post by Bob La Londe
Sans the solution I am looking for is there a better disc for stripping
metal than an abbrasive flap disc?  I can do the work with a grinding
wheel, but its much more skilled to avoid gouging the base metal and
doing damage.  I tend to only use a grinding wheel to make the bevels
before welding.
----------------
I cleaned the paint and rust from the 4" channels for the gantry hoist
track with an HF "2 in. Mini Orbital Air Sander" and a 2" coarse
scouring pad, the only power sander I own that fit flat inside the
channels. It was fast enough on the outside to satisfy my laid-back
retiree working rate. After stripping the four 8' channels it seemed
clogged with paint but still cut well enough to remove the leak-causing
corrosion from the rims of the aluminum motorcycle wheels the sawmill
blade runs on. I don't remember if there was mill scale under the paint
on the channels. The pad left shiny metal.
The HF tool was meant to be double action but it cut faster with the
rubber disk mounted to seat on the outer bearing race and spin instead
of oscillating.
The sander and the 2" and 3" pad kits don't work well together as
received. I made a stub arbor of 1/4-20 threaded rod and used nuts and
washers to control whether the pad spun or oscillated.
It seemed that a 3" pad on a 2" backing conformed to inside curves
better and may have been better on edge for shallow rust pits. Although
the used pallet rack channels had been stored outdoors they weren't
pitted enough to require my needle scaler or sandblaster.
My faster hand held metal flattening tool is a 7" angle grinder with a
saucer wheel. Unlike with the usual disk I can see and feel when it
makes contact around the arc and is cutting flat. I use it where welds
will be bolted together or support something, like the warped engine
mount plate on my second-hand log splitter.
Cleaning square tubing seems like a belt sander task.

I had not thought of that. I have one around somewhere, but have not
used it since my last cabinet building project a few years ago.

[Snag]

Post by Bob La Londe
Sans the solution I am looking for is there a better disc for stripping
metal than an abbrasive flap disc?  I can do the work with a grinding
wheel, but its much more skilled to avoid gouging the base metal and
doing damage.  I tend to only use a grinding wheel to make the bevels
before welding.
----------------
I cleaned the paint and rust from the 4" channels for the gantry hoist
track with an HF "2 in. Mini Orbital Air Sander" and a 2" coarse
scouring pad, the only power sander I own that fit flat inside the
channels. It was fast enough on the outside to satisfy my laid-back
retiree working rate. After stripping the four 8' channels it seemed
clogged with paint but still cut well enough to remove the
leak-causing corrosion from the rims of the aluminum motorcycle wheels
the sawmill blade runs on. I don't remember if there was mill scale
under the paint on the channels. The pad left shiny metal.
The HF tool was meant to be double action but it cut faster with the
rubber disk mounted to seat on the outer bearing race and spin instead
of oscillating.
The sander and the 2" and 3" pad kits don't work well together as
received. I made a stub arbor of 1/4-20 threaded rod and used nuts and
washers to control whether the pad spun or oscillated.
It seemed that a 3" pad on a 2" backing conformed to inside curves
better and may have been better on edge for shallow rust pits.
Although the used pallet rack channels had been stored outdoors they
weren't pitted enough to require my needle scaler or sandblaster.
My faster hand held metal flattening tool is a 7" angle grinder with a
saucer wheel. Unlike with the usual disk I can see and feel when it
makes contact around the arc and is cutting flat. I use it where welds
will be bolted together or support something, like the warped engine
mount plate on my second-hand log splitter.
Cleaning square tubing seems like a belt sander task.

I had not thought of that.  I have one around somewhere, but have not
used it since my last cabinet building project a few years ago.

If it has a dust bag , remove it and tape over the outlet . I learned
the exciting way ...

[Bob La Londe]

Post by Snag

Post by Bob La Londe
Sans the solution I am looking for is there a better disc for stripping
metal than an abbrasive flap disc?  I can do the work with a grinding
wheel, but its much more skilled to avoid gouging the base metal and
doing damage.  I tend to only use a grinding wheel to make the bevels
before welding.
----------------
I cleaned the paint and rust from the 4" channels for the gantry
hoist track with an HF "2 in. Mini Orbital Air Sander" and a 2"
coarse scouring pad, the only power sander I own that fit flat inside
the channels. It was fast enough on the outside to satisfy my
laid-back retiree working rate. After stripping the four 8' channels
it seemed clogged with paint but still cut well enough to remove the
leak-causing corrosion from the rims of the aluminum motorcycle
wheels the sawmill blade runs on. I don't remember if there was mill
scale under the paint on the channels. The pad left shiny metal.
The HF tool was meant to be double action but it cut faster with the
rubber disk mounted to seat on the outer bearing race and spin
instead of oscillating.
The sander and the 2" and 3" pad kits don't work well together as
received. I made a stub arbor of 1/4-20 threaded rod and used nuts
and washers to control whether the pad spun or oscillated.
It seemed that a 3" pad on a 2" backing conformed to inside curves
better and may have been better on edge for shallow rust pits.
Although the used pallet rack channels had been stored outdoors they
weren't pitted enough to require my needle scaler or sandblaster.
My faster hand held metal flattening tool is a 7" angle grinder with
a saucer wheel. Unlike with the usual disk I can see and feel when it
makes contact around the arc and is cutting flat. I use it where
welds will be bolted together or support something, like the warped
engine mount plate on my second-hand log splitter.
Cleaning square tubing seems like a belt sander task.

I had not thought of that.  I have one around somewhere, but have not
used it since my last cabinet building project a few years ago.

If it has a dust bag , remove it and tape over the outlet . I learned
the exciting way ...

Did you ignite a bag of sawdust or shoot sparks down your shirt? Either
way it sounds exciting. Did you by any chance get video?

[Snag]

Post by Snag

Post by Bob La Londe
Sans the solution I am looking for is there a better disc for stripping
metal than an abbrasive flap disc?  I can do the work with a grinding
wheel, but its much more skilled to avoid gouging the base metal and
doing damage.  I tend to only use a grinding wheel to make the bevels
before welding.
----------------
I cleaned the paint and rust from the 4" channels for the gantry
hoist track with an HF "2 in. Mini Orbital Air Sander" and a 2"
coarse scouring pad, the only power sander I own that fit flat
inside the channels. It was fast enough on the outside to satisfy my
laid-back retiree working rate. After stripping the four 8' channels
it seemed clogged with paint but still cut well enough to remove the
leak-causing corrosion from the rims of the aluminum motorcycle
wheels the sawmill blade runs on. I don't remember if there was mill
scale under the paint on the channels. The pad left shiny metal.
The HF tool was meant to be double action but it cut faster with the
rubber disk mounted to seat on the outer bearing race and spin
instead of oscillating.
The sander and the 2" and 3" pad kits don't work well together as
received. I made a stub arbor of 1/4-20 threaded rod and used nuts
and washers to control whether the pad spun or oscillated.
It seemed that a 3" pad on a 2" backing conformed to inside curves
better and may have been better on edge for shallow rust pits.
Although the used pallet rack channels had been stored outdoors they
weren't pitted enough to require my needle scaler or sandblaster.
My faster hand held metal flattening tool is a 7" angle grinder with
a saucer wheel. Unlike with the usual disk I can see and feel when
it makes contact around the arc and is cutting flat. I use it where
welds will be bolted together or support something, like the warped
engine mount plate on my second-hand log splitter.
Cleaning square tubing seems like a belt sander task.

I had not thought of that.  I have one around somewhere, but have not
used it since my last cabinet building project a few years ago.

If it has a dust bag , remove it and tape over the outlet . I learned
the exciting way ...

Did you ignite a bag of sawdust or shoot sparks down your shirt?  Either
way it sounds exciting.  Did you by any chance get video?

Lit the bag on fire , half full of sawdust . Ooops .

[Jim Wilkins]

"Snag" wrote in message news:t5h6df$n32$***@dont-email.me...

If it has a dust bag , remove it and tape over the outlet . I learned
the exciting way ...

--------------------------

I burn sawdust from the sawmill as part of the kindling in the wood stove.
Lying still it chars and goes out, but when picked up in an air stream it
roars like a jet engine and fills the stove with flame.

The air stream is from blowing into a 3/8" vinyl tube that ends in a 1/8"
nozzle, tapered inside and out to amplify airflow like an aspirator or steam
injector. Maybe someday I'll try dribbling sawdust into the forge blower.

[Jim Wilkins]

Post by Jim Wilkins
Cleaning square tubing seems like a belt sander task.

I had not thought of that. I have one around somewhere, but have not
used it since my last cabinet building project a few years ago.

----------------

When I was young I read of a college psychology experiment in which the task
was moving muddy water without utensils. There was a pitcher of water and
tumblers within sight, but no one either thought to or dared dirty them.

That inspired me to see what things -could- do rather than what they were
meant for, "outside the box."

For example I'm watching broadcast (not cable) news and weather on a laptop
I turned into a portable battery-powered HDTV that also records.

[Clifford Heath]

Post by Bob La Londe
Yesterday I found myself cleaning up a bit of square tube in preparation
for welding and later paint.  It was outside, but in SW Arizona, that
just means it has developed a small amount of protective rust over the
mill scale.
I started with an angle grinder and a flap disc.  It made short work of
the light loose rust, but would hardly touch the mill scale.  It also
showed some rust down "in the" the mill scale.  I probably could have
stopped there, but I got carried away with myself.  This stuff welds
really nice if you have bright shiny metal and takes a good paint coat
as well with an etching primer, and proper cure times.
I probably I could have just used extend or some other rust neutralizing
primer after knocking off the loose rust, but this construct will be
going into a humid environment.
I noticed a fresh flap disc stripped rust, and mill scale amazingly
fast.  It did more work with less effort in the first minute or two than
it did in the next ten.  Now the flap disc was still nearly new, but it
was performing like one that was half worn away.  There was still plenty
of grit, but the edge was mostly the flaps rather than the grit, and the
face was the same, but also gummed up with mill scale.
I am NOT trying to get longer life out of a flap disc.  I am trying to
get more time performing like the first minute or two of a new disc.  I
don't care if the total life of the disc is less.  Is there a practical
way to dress these so that you can expose more grit quickly.  I tried
spinning it against a wire wheel on a bench grinder.  The result was
less than amazing.
Sans the solution I am looking for is there a better disc for stripping
metal than an abbrasive flap disc?  I can do the work with a grinding
wheel, but its much more skilled to avoid gouging the base metal and
doing damage.  I tend to only use a grinding wheel to make the bevels
before welding.

I can't recommend a product, but my experience suggests that the rapid
deterioration has more to do with the quality of the adhesives used to
attach the grit than it does with the grit itself. The bigger sharper
particles of grit simply get ripped away, leaving you sad.

Find a product that uses a better quality adhesive. Maybe rated for
higher temperature or loads, or to be installed in large sanding
machines where it's tedious to change the abrasives.

Clifford Heath

[Bob Engelhardt]

I thought that flap discs worked by having the used-up edges wear away
and expose new grit. But that never happens for me. The various things
that I've tried to expose new grit have never worked. So either I'm
missing something or they just don't work that way. If I'm missing
something, I would really appreciate being clued in. If they don't work
that way, what is the point of having flaps?

[Richard Smith]

Post by Bob Engelhardt
I thought that flap discs worked by having the used-up edges wear away
and expose new grit. But that never happens for me. The various
things that I've tried to expose new grit have never worked. So
either I'm missing something or they just don't work that way. If I'm
missing something, I would really appreciate being clued in. If they
don't work that way, what is the point of having flaps?

I think I know what you and Bob are saying.

Answer is - sorry - don't know.

With a "hard" side-grinding disk - an angle-grinder "carborundum" disk
- if it gets blunt and clogged from lightly skimming over big-area
flat surfaces, you can sharpen it by crudely "wiping" the disk along
the edge of some chunky iron. Small area and big force = rip at the
disk surface. Have a heavy offcut of piece of scrap to-hand to
re-sharpen your grinding disk on.

I don't know of the same with a flap disk.
I've known them never clogging due to the flap construction and never
getting blunt through wearing-away and progressively exposing new
grit.
Do try the same trick of "wiping" harshly along a narrow edge on some
scrap?

[Dirtcrasher]

I have the exact same issue, the edge wears down and the disc stops working. The new material never exposes itself. I've sat down with thin, sharp shears and cut off the old to expose some newer material. I hate tossing away a 4$ item after such a short use..

[Bob La Londe]

Post by Bob La Londe
Yesterday I found myself cleaning up a bit of square tube in preparation
for welding and later paint.  It was outside, but in SW Arizona, that
just means it has developed a small amount of protective rust over the
mill scale.
I started with an angle grinder and a flap disc.  It made short work of
the light loose rust, but would hardly touch the mill scale.  It also
showed some rust down "in the" the mill scale.  I probably could have
stopped there, but I got carried away with myself.  This stuff welds
really nice if you have bright shiny metal and takes a good paint coat
as well with an etching primer, and proper cure times.
I probably I could have just used extend or some other rust neutralizing
primer after knocking off the loose rust, but this construct will be
going into a humid environment.
I noticed a fresh flap disc stripped rust, and mill scale amazingly
fast.  It did more work with less effort in the first minute or two than
it did in the next ten.  Now the flap disc was still nearly new, but it
was performing like one that was half worn away.  There was still plenty
of grit, but the edge was mostly the flaps rather than the grit, and the
face was the same, but also gummed up with mill scale.
I am NOT trying to get longer life out of a flap disc.  I am trying to
get more time performing like the first minute or two of a new disc.  I
don't care if the total life of the disc is less.  Is there a practical
way to dress these so that you can expose more grit quickly.  I tried
spinning it against a wire wheel on a bench grinder.  The result was
less than amazing.
Sans the solution I am looking for is there a better disc for stripping
metal than an abbrasive flap disc?  I can do the work with a grinding
wheel, but its much more skilled to avoid gouging the base metal and
doing damage.  I tend to only use a grinding wheel to make the bevels
before welding.

I tried a couple methods of dressing the flap disc. It would improve
slightly but not for very long. 5 seconds of work maybe. I already have
the flap disc so I figured I'd see if I could improve their usefulness
first before trying anything else.

These are 60 grit Zirconia discs, but results were similar with Aluminum
oxide flap discs as well.