Angle Grinder Safety

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The Medway Handyman

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Jul 21, 2007, 3:03:18 PM7/21/07
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Given my track record with angle grinders, I've been thinking about the
safety aspect.

My 9" grinder has a three position 'd' handle & a three position side handle
so when cutting vertically you can use it with the disc spinning upwards or
downwards. When its spinning 'up' all the muck is thrown towards the
operator (me), when spinning 'down' the muck is thrown down at the floor.

From the potential kickback situation, which is safer? If the disc catches
whilst spinning 'up' the machine would react by kicking down & away from me.

It seems better to put up with the muck & bullets because the kickback
threat is less.

Also, I assume a segmented diamond disc is more likely to kickback than a
normal abrasive disc?

Anywhere I can read up on this subject?


--
Dave
The Medway Handyman
www.medwayhandyman.co.uk
01634 717930
07850 597257


Lurch

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Jul 21, 2007, 3:07:33 PM7/21/07
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On Sat, 21 Jul 2007 20:03:18 +0100, "The Medway Handyman"
<davi...@nospamblueyonder.co.uk> mused:

>Given my track record with angle grinders, I've been thinking about the
>safety aspect.
>
>My 9" grinder has a three position 'd' handle & a three position side handle
>so when cutting vertically you can use it with the disc spinning upwards or
>downwards. When its spinning 'up' all the muck is thrown towards the
>operator (me), when spinning 'down' the muck is thrown down at the floor.
>
>From the potential kickback situation, which is safer? If the disc catches
>whilst spinning 'up' the machine would react by kicking down & away from me.
>
>It seems better to put up with the muck & bullets because the kickback
>threat is less.
>

Eh?

>Also, I assume a segmented diamond disc is more likely to kickback than a
>normal abrasive disc?
>

--
Regards,
Stuart.

Cicero

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Jul 21, 2007, 4:55:13 PM7/21/07
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==================================
The rule I learned is that you stand outside (i.e.to one side)the working
line of whatever power tool you're using. If you follow this basic rule
the danger from kickback is less dangerous than the danger from flying
debris from saw, grinder etc. Having dust and debris flying away from
oneself is generally safer than having it flying straight at you like dirt
from a terrier's legs.

ROSPA might have some guidelines on the subject, but I think this is a
topic where that wiki idea might be useful in gathering 'best practice'.

--
===================================
Using Ubuntu Linux
Windows shown the door
===================================

John Rumm

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Jul 21, 2007, 6:45:05 PM7/21/07
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The Medway Handyman wrote:

> Given my track record with angle grinders, I've been thinking about the
> safety aspect.

I always look forward to any post from you with Angle Grinder in the
title! Must be a form of morbid curiosity. ;-)

> My 9" grinder has a three position 'd' handle & a three position side handle
> so when cutting vertically you can use it with the disc spinning upwards or
> downwards. When its spinning 'up' all the muck is thrown towards the
> operator (me), when spinning 'down' the muck is thrown down at the floor.
>
> From the potential kickback situation, which is safer? If the disc catches
> whilst spinning 'up' the machine would react by kicking down & away from me.

Generally you want to be cutting such that any snag will tend to pull
the machine away from you, rather than lob either directly it at you,
or kick it in an arc that will eventually intersect with you. It also
helps if gravity is working in your favour. Say you were slotting a
vertical chase in a wall, then having the grinder no lower than head
height would ensure any kick will tend to pull the machine up and out a
little, but over your head. This would suggest that you bend your legs /
kneel as you progress the cut down. You also want to be cutting in a
direction such that the rotation of the disc is pulling the machine into
the work and not pushing it away in the same way as a circular saw does.

Having said that, I can't say I have ever had much of a problem with an
angle grinder kicking in the first place.

> It seems better to put up with the muck & bullets because the kickback
> threat is less.

You don't really want the ejected stream pointing straight at you
either, especially when cutting metal since it will be hot enough to set
you alight!

> Also, I assume a segmented diamond disc is more likely to kickback than a
> normal abrasive disc?

Other way around I find. Diamond discs offer less cut resistance and
remove less material in the first place.

> Anywhere I can read up on this subject?

Don't know. Search for "Angle Grinder safety" perhaps?

--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/

Chas

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Jul 21, 2007, 6:59:06 PM7/21/07
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On 21 Jul, 20:03, "The Medway Handyman"

My thoughts are that if you if you need to ask advice on the use of
this type of machine then you should NOT even be THINKING of using
it.
There are day/evening classes on the safe use of these and similar
types of cutters.

The Medway Handyman

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Jul 21, 2007, 7:03:59 PM7/21/07
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There are? Where?

The Medway Handyman

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Jul 21, 2007, 7:24:24 PM7/21/07
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Chas wrote:
> On 21 Jul, 20:03, "The Medway Handyman"
> <davidl...@nospamblueyonder.co.uk> wrote:
>> Given my track record with angle grinders, I've been thinking about
>> the safety aspect.
>>
>> My 9" grinder has a three position 'd' handle & a three position
>> side handle so when cutting vertically you can use it with the disc
>> spinning upwards or downwards. When its spinning 'up' all the muck
>> is thrown towards the operator (me), when spinning 'down' the muck
>> is thrown down at the floor.
>>
>> From the potential kickback situation, which is safer? If the disc
>> catches whilst spinning 'up' the machine would react by kicking down
>> & away from me.
>>
>> It seems better to put up with the muck & bullets because the
>> kickback threat is less.
>>
>> Also, I assume a segmented diamond disc is more likely to kickback
>> than a normal abrasive disc?
>>
>> Anywhere I can read up on this subject?

> My thoughts are that if you if you need to ask advice on the use of


> this type of machine then you should NOT even be THINKING of using
> it.

Why is it, that there is always some one who comes up with the "if you ned
to ask you shouldn't do it" argument. If we all thought that way we would
never progress or learn would we?

So, Chas. If you ever want advice on high pressure cleaners, carpet
cleaning, or vacuums I will reply (based on 30 years experience) that "if
you have to ask you should not even be thinking of it".

Robin

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Jul 21, 2007, 7:28:42 PM7/21/07
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I am *really* glad this question has been asked as I thought I was the
only noob who did not understand what the safety warnings mean in
practice.

What you say is what I have read elsewhere. But I have struggled the
few times I have taken my new toys for a spin to see how I can both
stand to one side and follow the marked line. That has not mattered
much so far as I've only been hacking off spurious bits of garden wall.
But it will matter next week when I am due tackle a couple of small
(600mm) cuts across a bit of concrete driveway. So if anyone can draw
me a picture (if only in words) I'd welcome it.

I did Google around but what I found was not clear. Some of it was some
scary. In particular there were many stories of discs disintegrating at
speed (so akin to an explosion ) but nothign very clear about how to
avoid that happening other than a recommendation to run new discs in a
protected area before using them. I am not sure how to do that without
special equipment. Is it general practice to do it please? Apart from
that is it mainly a matter of buying decent discs and not putting
excessive pressure on them?

Oh, and I did also look to see if there were day or evening classes
which would cover their use. There are none where I live (or at least
none open to a 50-something man who is not in drug rehab/serving out
community service/in receipt of JSA...........)

--
Robin


John Rumm

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Jul 21, 2007, 8:05:53 PM7/21/07
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Robin wrote:

> What you say is what I have read elsewhere. But I have struggled the
> few times I have taken my new toys for a spin to see how I can both
> stand to one side and follow the marked line. That has not mattered
> much so far as I've only been hacking off spurious bits of garden wall.
> But it will matter next week when I am due tackle a couple of small
> (600mm) cuts across a bit of concrete driveway. So if anyone can draw
> me a picture (if only in words) I'd welcome it.

To an extent you need to stand a little to the side to avoid the grinder
blocking your line of site of the line anyway. Assuming you are right
handed, If you hold the grinder with you left hand on the side handle
and have that inline with the middle of your face, and the right on the
base handle, then watch the line from the left side of the disc, you
will naturally be out of the line of kickback. Make sure the guard on
the grinder is positioned so that should it come flying toward you, it
is the back of the grinder or the guard that would hit you and not
exposed spinning disc.

> scary. In particular there were many stories of discs disintegrating at
> speed (so akin to an explosion ) but nothign very clear about how to

This applied to abrasive discs, not diamond ones. As long as you use
proper grinder discs (the correct abrasive discs are re-enforced with a
mesh of strong fibres), and you store them in a dry place, you should be
fine. The danger comes if you try using a damp disc or one not designed
for an angle grinder. (the small ones spin very fast - 11K RPM)

> avoid that happening other than a recommendation to run new discs in a
> protected area before using them. I am not sure how to do that without

Just sinning a disc up and running it for 15 secs or so while holding
the grinder away from your body with as little of you in the same plane
as the disc as possible will achieve this. Obviously make sure the plane
of the disc is not pointing at anyone else either.

> special equipment. Is it general practice to do it please? Apart from
> that is it mainly a matter of buying decent discs and not putting
> excessive pressure on them?

With masonry, use diamond discs. The only time the abrasive ones are
handy is when cutting very soft and abrasive materials, like some
limestones or asphalt. Even then you can get appropriate diamond discs
for these.

Make sure you have good face and hearing protection. If using goggles,
they need to be the indirect vented type and not those with a mesh style
direct vent (these will let red hot sparks enter the goggles when
grinding metal). A full face visor is preferable in many cases since
sparks or stone fragments just hitting your face will hurt. For masonry
work, respirtory protection is vital.

If using things like wire brushes then add a leather apron or many
layers of heavy fabric to the protective gear - much nicer than pulling
wire fragments out of the gonads.

There is a summary of all this here:

http://www.diyfaq.org.uk/powertools/anglegrinder.htm

John Rumm

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Jul 21, 2007, 8:14:34 PM7/21/07
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The Medway Handyman wrote:

> So, Chas. If you ever want advice on high pressure cleaners, carpet
> cleaning, or vacuums I will reply (based on 30 years experience) that "if
> you have to ask you should not even be thinking of it".

Have you stuck the completed version of the carpet cleaning FAQ on the
wiki yet?

Andrew Mawson

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Jul 22, 2007, 4:03:11 AM7/22/07
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"John Rumm" <see.my.s...@nowhere.null> wrote in message
news:46a28c75$0$1614$ed26...@ptn-nntp-reader02.plus.net...
>>SNIP<<

> Having said that, I can't say I have ever had much of a problem with
an
> angle grinder kicking in the first place

> John.


I did once get the opportunity to see my skeleton thanks to a 9" angle
grinder ! Cutting a length of 3" x 2" steel channel section, carefully
supported (I thought) so the cut tended to open rather than close.
Residual stesses in the channel pinched the blade, took a section out
of the cutting disk which started the whole thing flying round the
place on the end of its cable, taking a chunk out of my leg in the
process. Hospital were impressed how clean the cut was <G>

AWEM


Cicero

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Jul 22, 2007, 4:09:39 AM7/22/07
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==================================
I have occasionally seen people standing astride slabs and timber on the
ground whilst using circular saws and angle grinders. This seems to me to
be a dangerous method as any kickback is directly in line with the body.

The advice to stand to one side is actually the most natural method if you
consider the way you use an electric planer or saw to smooth / cut a long
piece of wood on a bench. As far as standing to one side when using an
angle grinder is concerned the technique is to hold the angle grinder away
from your body but not so far that you can't see the cutting line and
judge the correct cutting angle which is normally about 90 degrees to the
surface you're cutting. With a bit of care and practice you don't need a
direct line of sight to cut a reasonably accurate line.

I'm not too sure about disks 'exploding'. My experience is that disks can
break up but the bits tend to fly in line with the normal direction of
rotation so this is an additional reason to keep your head out of the line
of rotation.

Cic.

Robin

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Jul 22, 2007, 4:33:05 AM7/22/07
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Thank you both. Very helpful (and kind when I had forgotten to look in
http://www.diyfaq.org.uk/).

On the FAQ, I wonder if someone who has more experience might consider
adding that "exclusion zones" should be set up so other people can't be
hit by sparks etc or the grinder flails around. Obvious, I know, but
it's a point which was emphasised in some of the guidance I did find.
--

Robin


R

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Jul 22, 2007, 5:23:03 AM7/22/07
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"The Medway Handyman" <davi...@nospamblueyonder.co.uk> wrote in message
news:f7tl9t$fju$1...@registered.motzarella.org...

Have a look at
http://www.safetyline.wa.gov.au/pagebin/mechhazd0006.htm

Quite informative


meow...@care2.com

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Jul 22, 2007, 7:42:52 AM7/22/07
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"You also want to be cutting in a
direction such that the rotation of the disc is pulling the machine
into
the work and not pushing it away in the same way as a circular saw
does."

... a recipe for kickback. The rest is great advice though.


NT

Andy Dingley

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Jul 22, 2007, 9:12:06 AM7/22/07
to
On Sat, 21 Jul 2007 20:03:18 +0100, "The Medway Handyman"
<davi...@nospamblueyonder.co.uk> wrote:

>Given my track record with angle grinders, I've been thinking about the
>safety aspect.

Given my track record with them, and the record of people I share
workshop space with, the biggest improvement to safety is in having a
way to switch it off reliably. Especially if you're using an ArborCut
disk, you'll find that crud blocks the switches of all angle grinders,
from the cheapies to the good ones, such that they won't then turn off
when you want them to. Make sure there's an alternative one-handed
power switch nearby.

Also (Richard, I mean you!) don't leave plugged in and "live" grinders
lying on cluttered benches.


As to kickback, them IMHE this is caused by twisting the disk in the
slot and binding on the sides. Abrasive disks are worse than diamond,
even segmented.

John Rumm

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Jul 22, 2007, 9:43:18 AM7/22/07
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You think?

That would suggest the "normal" direction of cut would be to push the
machine away from you cutting with the far edge of the disc.

The only time I cut in this direction is on the first pass on masonry so
that you can see your cut line and not cover it in dust. Once you are
deep in a cut the natural and safer (IME) is to pull the machine rather
than push it.

John Rumm

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Jul 22, 2007, 9:45:31 AM7/22/07
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Yes, good idea.

The Medway Handyman

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Jul 22, 2007, 10:59:35 AM7/22/07
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Thanks for that. Makes an interesting point;
---------------------------------------------------------
Because angle grinders are designed for grinding and not for cutting, the
use of cutting discs with angle grinders exposes operators to even greater
risks.
WorkSafe Western Australia says:
Where a safer alternative cutting tool is available or can be obtained . . .
AN ANGLE GRINDER SHOULD NOT BE USED AS A CUTTING TOOL.

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

Hmmm!

Robin

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Jul 22, 2007, 11:15:15 AM7/22/07
to
I too found that interesting but, like so much of the guidance I found,
it seemed to focus on grinding rather than cutting (which is fair enough
given the Dave highlighted).

But my reason for coming back is to ask the advice of the angle grinder
Witan on cut-off guards (as in the bottom right picture on the first
page of
http://www.ind.carborundumabrasives.com/Media/Documents/S0000000000000001045/Safety%20-%20Mounting%20Cut-off%20Wheels.pdf).
They look like a good idea for cutting (but all I know is that looks can
be misleading).
--
Robin


Cicero

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Jul 22, 2007, 11:31:25 AM7/22/07
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==================================
I think what you're looking at is a cut-off guard with some kind of depth
stop. Most angle grinders have a simple cut-off guard (i.e. without
depth stop) like the one on the left of that page. The guard has a dual
purpose - to protect your hands from accidental contact with the grinding
disk and to direct the debris stream in a particular direction away from
the operator.

The guard can be moved to different positions to suit the cutting angle.
You can experiment with different positions to find the best position for
your cutting style.

Pete C

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Jul 22, 2007, 1:59:51 PM7/22/07
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On Sun, 22 Jul 2007 09:03:11 +0100, "Andrew Mawson"
<andrew@no_spam_please_mawson.org.uk> wrote:

>
>I did once get the opportunity to see my skeleton thanks to a 9" angle
>grinder ! Cutting a length of 3" x 2" steel channel section, carefully
>supported (I thought) so the cut tended to open rather than close.
>Residual stesses in the channel pinched the blade, took a section out
>of the cutting disk which started the whole thing flying round the
>place on the end of its cable, taking a chunk out of my leg in the
>process. Hospital were impressed how clean the cut was <G>

Hi,

When cutting something like this I try to have the edge of the guard
near the workpiece, such that if the disc jams the guard will brace
against the workpiece and stop the grinder spinning round.

cheers,
Pete.

Pete C

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Jul 22, 2007, 2:05:20 PM7/22/07
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On Sun, 22 Jul 2007 14:43:18 +0100, John Rumm
<see.my.s...@nowhere.null> wrote:

>meow...@care2.com wrote:
>> "You also want to be cutting in a
>> direction such that the rotation of the disc is pulling the machine
>> into
>> the work and not pushing it away in the same way as a circular saw
>> does."
>>
>> ... a recipe for kickback. The rest is great advice though.
>
>You think?
>
>That would suggest the "normal" direction of cut would be to push the
>machine away from you cutting with the far edge of the disc.

I tend to do it the same way it should be done with a router, so if
the blade starts to dig in too much it pushes the machine back out of
the cut instead of pulling it into the cut which can make the machine
jump away from the cut suddenly.

cheers,
Pete.

John Rumm

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Jul 22, 2007, 3:02:00 PM7/22/07
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With a router you you should only really attempt a climb cut (i.e. with
the direction of rotation) as a final last pass when you have a wood
that will otherwise suffer tearout. The main cut should be against the
direction of rotation (as with most other power tools etc). The fence or
the bearing on the cutter will prevent the tool being pulled into the work.

Pete C

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Jul 22, 2007, 5:07:31 PM7/22/07
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On Sun, 22 Jul 2007 20:02:00 +0100, John Rumm
<see.my.s...@nowhere.null> wrote:

>With a router you you should only really attempt a climb cut (i.e. with
>the direction of rotation) as a final last pass when you have a wood
>that will otherwise suffer tearout. The main cut should be against the
>direction of rotation (as with most other power tools etc). The fence or
>the bearing on the cutter will prevent the tool being pulled into the work.

Yup, that is what I meant but you put it a lot better than I could, so
with a grinder I go against the direction of rotation too.

cheers,
Pete.

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