Are surface grinders that dangerous?

Patrice Lemée

Patrice Lemée

Joined
Aug 13, 2002
Messages
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Thanks to some good advices I received, I decided to give the wheels a try before I doing the belt conversion. I did a little on-line search on how to use the surface grinder and also about safety. Well let me tell you, they make it sound like this is the most dangerous tool out there and that a wheel exploding and maiming, if not outright killing you, is a very likely possibility. :(

I understand wanting to make sure people are careful but is it as bad as it sounds?
Any special dos and don'ts that can guarantee mo major injuries? Or, since I may be a tad accident prone in the shop :o, should I just play it safe and go back to my belts conversion instead?

Thanks
 
I've ran one once at my work. To me, it didn't seem like anything I should worry about. I normally run a 175ton press brake, and that is far more "scary" to opperate than a surface grinder. Like anything, just pay attention to what your going to be doing and think a few steps ahead. I'm sure their has been bad accidents on this machine, but I can't/havnt seen anything to be a problem.
 
I have professional experience with a surface grinder, and they've never struck me as particularly dangerous, in fact I'd say they are one of the more benign machines in a machine shop. Most of them have large guards around the wheels, and the wheel is usually spinning on an axis perpendicular to you, so if it breaks up you might get sprayed with chunks, maybe a couple small bruises, but if you're wearing proper and quality PPE, you should be mostly fine.

You want to talk dangerous, a large open bed engine lathe is about as dangerous as it gets. It will rip you to shreds in an instant if you screw up, or if something goes really wrong with a fixture or part.

I've been working around surface grinders for 2 decades and have only seen a wheel come apart twice, and in both cases the wheel never should have been mounted in the first place. That's not to say it doesn't happen out of the blue, but it's usually due to something like a damaged wheel, overheating or improper installation, or failure to dress properly.

The main danger I've personally seen is kicking a part, but once again, it's not shooting at you unless you're standing in a stupid spot.


Clean = Safe

Make sure the bore and spindle, spindle nut, etc. are clean and free of grit when mounting wheels. Make sure there are no large chips or damage on the wheels, if the wheel doesn't crack up, it will still do a number on the spindle bearings if it is significantly out of balance.

Make sure that the magnetic chuck or other fixture is clean and grit free when mounting a part. Make sure the part is clean and grit free, and has no high spots. The mag chucks grab amazingly hard, but only in the right conditions.

Watch your wheels for loading, essentially insure that the surface stays clean and free from obstructions or buildup that could cause heating or excessive friction.
 
I don't have one, but have used a couple. I don't see why a belt would be that much safer. Still a lot of stuff spinning. I would never stand inline with the grinder. If the piece being ground came off the magnet it could launch pretty good. If a wheel should grenade on you the pieces would fly inline with the grinder. I would keep all the guards on off course and wear the eye protection and at least a canvas shirt. I would also make sure the line of fire for the sparks was shielded so that the sparks and grit were contained and directed to down and away. How many times have you used a bench grinder, they have the same possibilities for stone failure. I would treat and store the stones with respect, only run stones that where rated for your machines RPMs, never run a damaged stone etc etc. With your power feed I would make sure that you didn't have it try to feed to much metal to the wheel. I knew a woman who worked for a place that made stones and she said they were all tested to a high RPM before shipment. I don't know if all companies do this.
 
Any tool can be dangerous, hurt you, maim you, kill you etc....
The biggest risk, however, is typically not the tool in question. It's complacency and carelessness.

I recently bought a surface grinder. I took it apart, cleaned it, repaired some odds and ends, got it wired up and put my first wheel on.
I pushed the spindle power on button, and within a split second I heard a loud bang as the wheel disintegrated and sent all kinds of pieces, small and large, in every direction of my shop. Some of them I still haven't found.

Why did this happen?

I was careless. I used an old, well worn wheel, that was sitting on the grinder when I bought it. I had no idea if it had been dropped, banged, chipped, etc.... other than a very casual (and careless) visual inspection. I also did not "ring test" the wheel. Grinding wheels should have almost a metallic ring when you tap them. Stick your finger through the hole of a wheel, and lightly tap the outside with a wooden hammer handle. If it rings, it's likely good. If it "thuds" it's probably got a crack/fracture in it somewhere, that is likely to propigate at 3600 RPM.

Is this a completely fail safe method of checking wheels and ensuring safety? Not necessarily. But it's better than nothing.

You should always have glasses on when operating the machine, and some even recommend a full face shield when first turning it on.


The second biggest risk is kick out of a poorly secured piece. Turn your magnet on after placing your stock, and try to move the stock with your fingers. If it moves by your finger, it will move by the wheel. Some parts will need to be "blocked" in, or even fixed into a jig or a vise.

Lastly, just don't hog material off, and you'll be ok. I rarely take more than .001" off at a time, and a lot of times, it's closer to .0005. If you start trying to hog off .002 or more at a time, your wheel is likey to grab the piece, or start glazing over. Having the right wheel will mitigate this somewhat, but SGs are precision machines, and not really made for taking off a 1/16th of an inch at a time anyhow... ;)
 
before you put any stone on a grinder arbour you need to ring test it. its like pottery if it doesn't ring when you tap it then it has a flaw in it and should not be used. If you have more then one stone then give them both (all) a tap you will here a ring ,,if one does not ring like the others then it is flawed and don't use it. Best way it to check you tube and check out some videos then you might have abetter idea of what I am talking about.
 
Thanks guys, I do feel safer with your instructions. First thing I need to do is to get some new wheels. I will also looks at what videos I can fond on youtube.

I am also thinking about an “automated face shield” like I have on other machines. I wear prescriptions glasses but these are not safety glasses and I know I'll be lazy from time to time and not reach for the safety glasses. Plus they are not the most comfortable to wear over the prescription ones.

I'll keep you posted on any safety features I add.
 
Patrice you should invest in some safety glasses with prescription lenses. You should be able to get a pair with UV and scratch protection for around $100. There are a variety of makers and styles. Some on the net that you sent them your Rx and the sent back. Lots of guys where I used to work ran them instead of the safety glasses over the top deal. You can also get a set of removable side shields that slide onto the bows of regular glasses. They may not be certified, but good plastic lenses and frames would usually meet the Z87 standard even if not certified. But, getting a pair of shop glasses and keeping your "dress" glasses from the effects of shop dust and dings isn't a bad idea anyway especially when you factor in the built in safety glasses deal.
 
Thanks Jim, that's a great idea and something I should have done a long time ago. Glasses are so expensive here (my dressed pair cost me around 800$) so I did not want to spend that much but safety glasses might be cheaper and even if not that much, it is still nothing compared to my eyesight. I appreciate your help. :thumbup:
 
They are nothing like "real" glasses, and the are not for everyone but if, like me, you only need glasses for closeup work (I'm at the age where various bits stop working like they used to) a pair of 3M BX Readers or similar may be worth investing in. They are bifocals with a reader prescription in the bifocal bit of 1.5, 2.0 or 2.5 diopter.

http://solutions.3m.com/wps/portal/...nt/Products/Product-Catalog/~?N=5158351&rt=c3

I'd expect other manufacturers to offer similar products.

Cost seems to be about 2 1/2 times the cost of comparable plain safety glasses here in the UK.

The good points are that I no longer have to take off my safety specs to put my normal glasses on every time I want to read something, they are reasonably cheap and they are reasonably comfortable.

Bad points are that the bifocal bit stands proud of the rest of the lens, so that is where all the scratches happen. I get through them about twice as fast as plain safety specs as a result.
 
Just wanted to thank you guys again for convincing me to get some real prescription safety glasses. Ordered a pair last week. Nothing fancy, a couple hundred bucks but definitely something I should have bought a long time ago. :thumbup:
 
The ring test goes back a very long time !! Pottery and grinding stones .especially important in natural stones It only takes a second and can save you from disaster .
 
I agree Don. But in my case, I still need protection for when laziness is stronger than common sense. :o You know when “it's only deburring a small part, no need for mega protection for that and the glasses are all the way on the other side of the shop (meaning a whole 10 feet in my case)”. You know that's the time when that small metal fragment will find your eye like it was laser guided there. :( That's why I have a few “automated” face shields in the shop. Better safe than sorry. Oh and also why I stopped wearing “crocks” when I weld. ;)

Thanks mete, I did learn about the test and use it regularly.
 
I'll chime in, Patrice. Lots of good advice in here!

I like the idea of your automatic guarding, which has become - along with proper PPE - the standard for OSHA and ANSI safety requirements. I feel that we err on the side of caution these days, but the consequences of losing a finger or an eye - especially for us knifemakers - is too grave to think about.
 
On the subject of PPE for the eyes- I am nearsighted, and wore glasses in the shop and when working construction in the past. They'd get so beat up, and be such a hassle to wear safety glasses and a respirator over, I just went to contacts. Now safety glasses are no problem.

Just a thought, anyway. I know I prefer them.
 
I hope this guy "ring tested" that stone wheel. I don't even want to think what would happen it that thing grenaded :eek:
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Pic from Higorokami corp.
 
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