Operating bench grinder using CBN wheels without guards?

[Steve Mathews]

I'm all for safety but the question about whether to use a guard on a bench grinder running CBN wheels has me stumped. Using guards with aggregate wheels is an obvious no-brainer but it seems to defy logic in using them with CBN wheels. Hopefully a discussion about this may shed some additional light on the question.

The primary argument for not using a guard with CBN wheels seems to be that they are not capable of disintegrating like aggregate wheels, which apparently is the primary reason the guards were developed. I don't know for sure if a CBN wheel can in fact break apart but it seems highly unlikely. By comparison, when do you ever see a similar guard used on a metal lathe where rotating metals take place? The other argument for a guard is for dust collection. Again, it's apparent that aggregate wheels generate some particles taken from the grinding wheel and whatever is being ground but it seems to me that the later is virtually the only byproduct of a CBN wheel. Is it really necessary to use a guard for collecting ground particles or is there a better way? Another factor to consider in our application is that most of the grinders used are slow speed thereby minimizing the dynamics that come into play. A plus for not using a guard seems to be that better visibility is afforded without them. Although not directly related to safety, better visibility of the working area can enhance it.

Well, that's my thoughts on the matter. What say you?

[Tom M King]

No guard on mine. I don't use it much, but when I do, I lay a couple of wet paper towels under it to catch the chips. The paper towels have to be wet enough so they stay in place without getting blown out of position. The junk thrown off seems to not go all the way around the wheel, but comes off pretty soon past the point of grinding. You can even see the most dense area on the wet paper towel that catches it. Mine is full speed, so it might get thrown off faster than a slow speed grinder.

[Dwight Rutherford]

No guards for me. Do have rare earth magnets under the wheels to collect metal fillings.

[John K Jordan]

I don't use the guards and do not yet collect the dust, but need to. I have some magnets stuck to the back side of my bandsaw about 10' away from the CBN wheels. After some use I noticed the magnets coated with extremely fine steel dust. In bright light at the grinder I can see the steel dust floating in the the air. Can't be good for the lungs - I wear a mask but what about that out in the shop? Run the air cleaner on the ceiling?

JKJ

[John King]

Ditto Dwight above. - John

[Curtis Myers]

I use a magnet shroud to collect the grinding dust. Works well. See below thread on the subject.
http://www.sawmillcreek.org/showthread.php?244731-Using-Magnets-to-control-grinding-dust

All the Best
Curt

[Reed Gray]

I still don't have a hood for my CBN wheels, but will keep the wheel covers on as much as possible, which means the part up against the grinder. I saw where some one, no idea who, put a spacer on it so they could put the outside on. I would have far more confidence of that working than magnets, or if the magnets are there as well, that might get most of the dust.

robo hippy

[Jamie Straw]

All this talk of magnets (a shop aid I love, BTW), I must raise a flag of caution: If you use a magnet to collect the metal dust from your CBN grinding wheel, be sure it is fastened securely such that it can't get grabbed by the wheel and thrown. I know one person this happened to, and he felt extremely lucky he didn't get nailed by the magnet as it flew across the shop. He'd been using it for months, no problem, and then wham!

[Larry Frank]

I would have some concerns about hot sparks starting a fire.

[John K Jordan]

I assume the magnets were pulled into a steel wheel by the magnetism? If so, not an issue for the aluminum wheels. Around the shop I usually use the magnets with countersunk holes and fasten them up with screws. A removable holder could be devised.

Has anyone using the magnets experimented with placing magnets around the back, top, and sides of the wheel? I wonder if a magnet placed in a single position would catch enough of the fine steel dust.

As for the fire hazard, unlike the conventional grinding wheels I've never seen heavy sparks from my CBN wheels, only an occasional weak spark that was extinguished far before it even reached the table. Are others seeing lots or long persistent sparks?

JKJ

[Reed Gray]

The brand new wheels do put off more spark than my old broken in ones. I have a bench top air scrubber that might pull in the dust, but the grinder needs to be hooded. I have heard of wood shavings in the wheel cover and CBN wheels starting to get a red glow, but not sure if there was a fire. So, still more experimenting to do...

robo hippy

[Terry Vaughan]

There's another reason for enclosing the wheel, which is to reduce the risk of entanglement. Long hair or loose clothing might get dragged in, particularly with a coarse grit wheel that would be more grabby.

I can't say how serious the danger is, but it is something else to consider.

As for the metal dust, it's possible to detect that right across the workshop. Magnets collect dust wherever they are, and sparkles can be seen in a flame after grinding. Some of the dust is very fine.

[Geoff Whaling]

A couple of responses have already touched upon some good reasons to keep guards on grinders, to reduce the hazards & risk from,


inadvertant contact with wheels,
fire from hot work - sparks
entanglement
falling objects - vibration causing objects to fall from shelves, or an item leaning against the grinder bench contacting an exposed wheel in our nice tidy workshops
metalic dusts
flying particles - sparks & eye injury; or objects
damage to the CBN wheel from 4 above
wheel or coating disintegration


Admittedly the risk from some hazards is significantly reduced due to the inherent design of CBN wheels, that we may consider that they are remote but they are not completely eliminated. The probability may be so low that we may be lulled into thinking that they are "impossible." Other risks are also significantly reduced from our other safety and hazard management actions - like restraining long hair & loose objects, maintaining a clean & tidy workshop with good ergonomic design etc.

One hazard we always have to manage is the "us or people hazard" - mostly we are an older bunch so medical issues, slips, trips and falls are becoming more probable. A grinder running with exposed wheels, CBN or friable, makes such an event even more likely to inflict severe injuries.

[Geoff Whaling]

By comparison, when do you ever see a similar guard used on a metal lathe where rotating metals take place?

The hazard profiles of a grinder and a metal lathe have some common factors but they have a different risk / probability profile. Grinders tend to run at a higher and typically fixed RPM with no ability to change speed. A grinding wheel also has a much higher peripheral wheel speed than typical recommended cutting speeds on metal lathes plus the work piece / cutting tool on a metal lathe is generally flooded with coolant. The operations are similar - removing metal, but the probabilities of potential events occurring are quite different.

Most OHS authorities recommend guarding of metal lathes with interlocked guards so that the work piece cannot be accessed by the opperator while the lathe is in opperation. In fact it is a mandatory requirement in many jurisdictions now.

[Ned Ladner]

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Wow. I've pocket dialed before but never pocket posted on a forum.

My apologies.

[Doug Rasmussen]

Is there even a question about guarding a spinning abrasive wheel?

Of course you should have a guard.

[Justin Stephen]

Is there even a question about guarding a spinning abrasive wheel?


There is for me. The main reason why I would never use a bench grinder with a traditional stone on it is not dust protection, but to offer at least some protection for my face should the stone ever fracture and come apart. That is a non-issue with a CBN wheel. If dust is a big concern, wear a mask. I will also say that the shrouds that came with my grinder would in no way cover my much wider CBN wheels.

[Doug Rasmussen]

There is for me. The main reason why I would never use a bench grinder with a traditional stone on it is not dust protection, but to offer at least some protection for my face should the stone ever fracture and come apart. That is a non-issue with a CBN wheel. If dust is a big concern, wear a mask. I will also say that the shrouds that came with my grinder would in no way cover my much wider CBN wheels.

There are issues other than a CBN wheel "exploding".

You have a spinning object under power. Long hair, even a long beard, loose clothing all could be entangled in the wheel and it's shaft. How about somebody tripping and falling face first into the wheel? Or backing into it if it's on a stand.

Somebody in another thread mentioned their grinder spun for minutes after the power was off. Just great having the turned off grinder coasting with exposed wheel when everyone thinks it's off.

Obviously, a lot of you have never worked in an industrial environment where guarding of a grinding wheel is a no-brainer.

Not to be too rude, but it's stupidity to debate such an issue.

[Dwight Rutherford]

How does this differ from spinning a chunk of wood at high speed and sticking a gouge into it? Do we all use the cage that comes with some lathes? I don't.

[Steve Mathews]

Not to be too rude, but it's stupidity to debate such an issue.

If it's stupidity to not use a guard then a discussion on the issue is healthy because many do not use them with CBN wheels. I don't know what's correct but many things pointed out in this thread make sense. The last point by Mr. Rutherford is quite interesting to consider.

[Justin Stephen]

You have a spinning object under power. Long hair, even a long beard, loose clothing all could be entangled in the wheel and it's shaft. How about somebody tripping and falling face first into the wheel? Or backing into it if it's on a stand.

Frankly, while the area of exposure would be lessened with a guard, it seems to me that the risk of entanglement from long hair or loose clothing would actually be worse with the guard on as it provides an additional surface for it to be trapped against. And yes, I have worked in an industrial environment and yes, we did have guards on the bench grinder, but that was before CBN wheels were even available.


Not to be too rude, but it's stupidity to debate such an issue.

To each their own. Honestly, I have been in several shops with CBN wheels and have only seen guards once that I recall. I guess Dave Schweitzer doesn't see the need for guards:

https://www.youtube.com/watch?v=Bk14XNP7ixM

Or Ken Rizza:

https://www.youtube.com/watch?v=qw6bjWkwaYs

Others do, and more power to them. If the guards that came with my grinder would fit, I probably would have put them back on (mostly so they wouldn't take up space in my tool box).

[Terry Vaughan]

As Doug points out, the shaft is a hazard. Entanglement happens when something wraps around the spinning object, which may be easier with the smaller diameter shaft. I would think the guard would make that less likely. Fatal accidents have happened when clothing is caught by a rotating shaft. Power take-off shafts of course, but also pulley shafts for example. Normal good practice like covering long hair and not wearing a tie or loose scarf would reduce risk. I'm not saying this is the most dangerous thing in the workshop, but I can predict that there will be entanglement accidents on unguarded CBN grinders as they become more widely used.

Industrial practice may not be the best guide, I've seen unguarded grinders in use with old stone wheels in commercial shops, and worse things too. And other people's practice may not be either.

The hazard is also present at the lathe, but the guard on a grinder is 'fit and forget', so one less thing to worry about.

[John K Jordan]

There are rotating hazards everywhere for people with loose clothing and loose long hair. Engine work, bench grinders, electric drills motors, wire brushes and cut off wheels on angle grinders, disk sanders, buffing wheels, milling machines, metal lathes and wood lathes, electric mixers in the kitchen, PTOs on tractors, brush cutters, lawn mowers, chippers, weed eaters. A CBN wheel is not a "grabby" device for clothing such as sleeves compared to some of these. Wire brushes are among the worst.

I've never seen a guard on a shop drill press which has a high rate of hand injury. Some tools should simply not be operated by children or uneducated, simple-minded, klutzy, or distracted adults.

My opinion is that people who tend to reach over, lean near, or let their hair down around rotating machinery might want to think about another hobby. I suggest painting with water colors. Watch out for the dangerous stapler. Don't stab the wooden end of the paintbrush in the eye.

JKJ

[Terry Vaughan]

Those machines cause accidents and at least some normally have guards, or should do. It would be strange if there were no correlation between having a guard fitted and the number of accidents. I agree about wire brushes, they can grab when they are not even moving. Drill presses come with chuck guards to stop scalping accidents, but whether in a commercial or a home workshop the guards usually get removed. My view is that a CBN wheel is on the lower end of risk for a sensible user, but that if a grinder comes with a guard it makes sense to use it.

In the home workshop people can make up their own minds, and if they can't follow basic good practice with long hair etc they are asking for trouble. Maybe water colour painting would be better for them.

[Geoff Whaling]

Those machines cause accidents and at least some normally have guards, or should do. It would be strange if there were no correlation between having a guard fitted and the number of accidents. I agree about wire brushes, they can grab when they are not even moving. Drill presses come with chuck guards to stop scalping accidents, but whether in a commercial or a home workshop the guards usually get removed. My view is that a CBN wheel is on the lower end of risk for a sensible user, but that if a grinder comes with a guard it makes sense to use it.

In the home workshop people can make up their own minds, and if they can't follow basic good practice with long hair etc they are asking for trouble. Maybe water colour painting would be better for them.

Machines don't cause "accidents"!

Injury events involving machines have many causes, which may be attributed to the operator, level of training, working environment, work practices, initial design, manufacture, installation, use, maintenance, modification and storage.

The design of machines and their construction may present hazards while they are in operation and some even while they are static i.e. unguarded cutter blades on a jointer / surfacer. Machines in operation present additional hazards i.e. exposed rotating shafts, moving parts, kick back on table saws, entanglement of loose sleeves on lathes.

Hazard controls include active and passive measures one of which is fitting machine guards to prevent or inhibit access to or contact with rotating parts, nip / crush points etc. Mostly they are simple fit and forget engineered and mostly passive devices, others can be very sophisticated moving screens with interlocks etc designed to only open or permit machine operation if a specific range of conditions are met.

It is the operator’s responsibility to learn how to setup and how to follow “safe work practices” for a tool, machine or other plant; how to minimize risk to themselves and others nearby. The operator can be a hazard to themselves and others, through not learning or seeking assistance; under estimating risk, taking shortcuts etc.

Generally "accidents" are the result of a combination of hazards.

In this instance with a "bench grinder," the machine was designed and supplied with narrow guards to suit a particular recommended width and diameter of friable wheel.

The hazard profile presented with the use of a bench grinder may include the typical, entanglement with rotating parts; contact hazards; metalic and mineral dusts; hot work; flying objects; poor work practices; poor attention to housekeeping practices; a trip; a medical condition; prescription or other drugs, tiredness, distractions; or pushing the limits of the intended use of the machine, jigs & tools to be sharpened.

Plus the modification of the machine operation - fitting wider CBN wheels; deliberate re-design to "solve a problem" - removing guards to fit the wider wheels; unawareness of the true hazard / risk profile of a "bench grinder" and the numbers of injuries resulting from the operation of a "bench grinder"; denial or lack of acceptance of the risk profile and injury rates.

Some or perhaps even all of these may feature in an "accident" while using a "bench grinder."

As users of tools and machines we must take action to lear to hopefully address and control all of these hazards to lower the risk of damage or injury to within acceptable limits. Grinders and bench grinders rate highly in DIY & hobby injury statistics.

Changing over from friable wheels to solid machined CBN wheels markedly changes the risk profile for some hazards. However the other hazards remain, and we may introduce new hazards, no guards, or increase the probability of and potential severity of injuries from the existing hazards. With a traditional wheel guard there is a much lower chance of contact with the exposed sector of the wheel than there is for a totally unguarded wheel in a trip or falling object event. With the guard it becomes a close call or near miss, without the wheel guard it is most likely an injury sufficient to warrant a hospital visit.

Currently there is little legislation to control the activities of hobbyists. However unacceptable rates of injury, the severity of injuries and the impact and cost upon our loved ones, families, hospitals, rehabilitation services etc does draw attention from authorities and legislators as was clearly the case with the high level of table saws injuries in the USA and the push to mandate “saw stops” etc.

[Jonathan Sidhu]

I've a 8" delta 23-880. The cbn wheel I am using from woodturnerswonders is 1.5" wide. In order to mount, the guards appear to need to be removed.

As this model has a tool rest mounted to the guard what would the forums suggest as an alternative tool rest?

[Reed Gray]

Grinder tool rests are kind of like the bandsaw blades that come with your saw, pretty much scrap metal. There are a couple of after market ones available. Stuart Batty makes one, Oneway has a whole grinding/sharpening set up which 95% or so of woodturners seem to have and it has a nice platform, Lee Valley had one, there are a couple of others from some of the catalogs. Not sure if it is proper, but I make one as well, and google my alias,

robo hippy

[John K Jordan]

Grinder tool rests are kind of like the bandsaw blades that come with your saw, pretty much scrap metal. There are a couple of after market ones available. Stuart Batty makes one, Oneway has a whole grinding/sharpening set up which 95% or so of woodturners seem to have and it has a nice platform, Lee Valley had one, there are a couple of others from some of the catalogs. Not sure if it is proper, but I make one as well, and google my alias,

robo hippy

I'll say it out loud: Reed Robo Hippy makes what looks like a well-thought out tool rest, easy to set a repeatable angle.
http://www.robohippy.net/store/robo-rest-ow-oneway-compatible
I don't have one because I'm too poor, er, cheap, but I might some day. I've read reports from several people on other forums who love this rest.

(No, I'm have no dog in this race and get nothing for my comments. I would love for Reed to visit some day if he gets over this way!)

BTW, I agree - I always throw away the tiny rests that come with grinders. Well, I throw them into a box.

JKJ

[Jonathan Sidhu]

Ty very much

[Roger Chandler]

I have two 1.5" CBN Wheels, and a grinder where I can keep both guards on. That Grinder is industrial rated, and also has a dust collection system on it in which the shrouds are an intregal part of dust collection. I like safety, and even thoough I am not in the least worried about the CBN wheels coming apart, I am proactive about dust and contact hazards. I had to pay a little extra for that grinder vs. the standard variety, but my grinding setup is optimal for good sharpening and for safety. I also use magnets, and only connect the shop vac to the grinder after a few minutes have passed, so as to make sure there are no hot metal particles.