Sharpeners in shops

[Jim Silva]

The thread about "Getting a Sharp Edge" by Odie got me thinking again of shop sharpening stations. I've been struggling with this for a bit now and would like some input.

My shop is 60' X 30' with the front half being general purpose/metal and the back exclusively woodworking. (mostly cabinetry and turning) While I love working with green wood, nearly all of my bowls are left to dry and re-turned so are very dry at final turning. In addition, the majority of my business (turning and otherwise) uses only kiln dried lumber and a high degree of fine scraping/sanding. As a result I generate far more talc-like dust and dry shavings than I suspect many of you do in the shop.

While I use dust collection at each station and take pains to sweep/vacuum the shop several times a week, there's always dust and shavings collecting in corners of machinery, floors, tables etc. As a result I've always kept my slow speed grinder (80 & 120 grit wheels) in the metal shop, fearing that a wayward spark from sharpening could result in fire. I'm unaware of any systems other than water-wheels that completely prevent sparks however diminutive yet I see time and time again folks here and elsewhere with non-water sharpeners set near their lathes. Am I being overly cautious, are they being overly reckless or is the fact that I'm dealing with much more volume of dry waste than those with say home or hobby shops a legit concern?

I'll admit to being a bit cautious where fire is concerned, mainly as I've seen how easily it starts. I've lived through a dust explosion in a commercial milling shop when dust ignited through static electricity so I ground all my dust collection hoses as any I don't will spark enough to hurt in the dry winter conditions I have here even with a humidifier.

Am I worrying over nothing in regards to fire hazards from grinding sparks or is it something that others are overlooking? I'm getting tired of the walk to the cold front shop just to touch up an edge or two.😱

Jim

 

[Odie]

Jim.....

Convenience is one of the major factors that will keep "the flow" going.....and, there just isn't anything that will do that better than having everything you need close to the lathe, and handy.

Your concern about fire hazard caused by grinding sparks igniting wood chips/dust is valid. I often wonder about that myself.....there is lots of sanding dust and chips in my shop. My grinder is on a pedestal, and it's one of the items I always blow off with air prior to leaving the shop.

I don't know if that's good enough, but I've never had a fire from grinding sparks.

Has anyone had a fire due to grinding sparks?

ooc

 

[Wayne Spence]

Yes-I too wonder about that. Are there any OSHA rules concerning the matter?

 

[David Somers]

Has anyone had a fire due to grinding sparks?

ooc

I have never even had a hint of a fire. But, I tend to clean up stuff as I go. I dont like shavings and sawdust all over. And, both in Seattle and my shop in HI, I have the tailstock of my lathe near the garage door. I almost always work with that open. Because of that positioning my sharpening station/tool rack gets rolled into the garage door area and set so any sparks go outside onto the driveway. I hadnt done that consciously however. On thinking about it, the setup makes some sense. Ignoring of course, the fact that I am working with a garage bay open in winter in Seattle, or while SO2 levels are wicked hi in HI from the volcano.....even lunatics can accidentally stumble on a moderately safe practice you know! <grin>

Dave

 

[Richard Baker]

Jim,
If the grinder in question is dedicated to sharpening (not grinding and reshaping) lathe tools, you are being overly cautious. The usual sharpening requires a light touch against the wheel, and the sparks are tiny and short lived. On the other hand, if you are doing any sort of heavy grinding, it is probably best done in the "metal shop". In any event, it might be a bad idea to locate a DC intake close to a grinder. It takes a fairly high dust concentration to ignite, similar to what might be seen swirling around in the collection bag of a DC.

 

[john lucas]

I worry about it because I grind a lot of metal when shaping things on my old Craftstman grinder. It sits on a wooden bench with wood stored below it. The sparks fly a lot. I never leave the shop after grinding on this grinder until I feel comfortable that I don't have a problem.
I have had a lot of dust near this grinder because it's also very near 2 sanders. Still so far I have not had even the hint of a problem. The sparks kind of burn my hand but I don't really think they are hot enough to start a fire.
I've talked to a fireman friend about dust explosions. He said that you would need a huge amount of airborn dust to make it happen. He talked like you wouldn't even stay in the room if it was that dusty.
I run a kerosene or propane heater and worry about that also. I had my dust collector bag blow off one day and I started to panic but not problem.
I still think we need to be as cautious as possible. Fire is not a good thing.

 

[Matt Owen]

I've done a lot of grinding with dust and shavings everywhere, and nothing has ever happened. The sparks are incredibly hot, but are very small and burn out very quickly. If you have ever tried to start a fire with flint and steel on twine, you know how hard it can be to get it lit, and that is when you are intentionally trying to start a fire. Being cautious is a good thing, but I think worrying about a fire cause by grinding sparks should be a minimal worry. Just my $.02.

Matt

 

[Jerry Hall]

Beware of sucking sparks into your DC system

It seems to me if you have so much dust in the air of your shop that it will ignite you are likely to die perhaps first of respiratory failure. But I wouldn't suck sparks or metal filings into my Dust Collector. That may well define the phrase: "It Sucks" in an ultimate way. In fact my Oneida specifically warns against non wood particles. This link reports on "dust" explosions of several types:
http://www.osha.gov/dts/shib/shib073105.html

I found this of some interest:
Fire Hazards
Collectors are highly susceptible to fires due to the presence of fuel (dust particles) and oxygen. Collectors have fan flow that further contributes to the fanning of a fire and helping it grow. Since collectors contain all these fire-friendly characteristics it is necessary that proper filter media is chosen and operating techniques are followed with care. There are many dusts that burn (form a fire) but they have a low rate of combustion.

Causes of Fire
The main causes of fires are (i) sparks and (ii) spontaneous combustion.
Sparks:
Sparks find their way into dust collector systems from the industrial process. They enter through the hoods and ducts in the collector system. One way of tackling sparks was by having a long duct. Traveling along the long duct would enable the spark to burn itself out or cool off. However it is not an effective solution since sparks are known to travel over a 100 feet and survive the cyclone before igniting the bags and dust in the dust collector. Fires in dust collectors start when the system is in process.
To understand the nature of the sparks we may look at the example of a campfire where sparks fly over the fire. Though sparks consist of a heavy particle, they ‘fly’ because they are surrounded by a layer of ‘hot air’. This layer of hot air around it makes the spark behave like a hot air balloon and it travels long distances easily. Dust collector systems have a smooth flow duct design which helps sparks to travel unaffected by gravity and centrifugal forces of the system.

Spontaneous Combustions
Fume dusts are a classic case of fine dusts that have large surface areas. Fume dusts are known to oxidize and the process of oxidation produces heat which is a factor that can start a fire. Oxidation does not cause a problem when the dust collector is in operation since the heat is removed by the flow of dust through elements. However when the dust collector is not in operation, heat generated by the oxidation of these dusts forms hot spots on the filter cake. These hot spots in the filter cake could ignite when the flow is restarted in the system. Once ignited the fires are fanned by the airflows and cause extensive damage.

Ways to Control Sparks
To extinguish sparks, it is essential that the layer of hot air surrounding the spark is removed. This can be achieved by creating a change in air velocity. The change in air velocity creates eddies in the air stream and removes hot air from the spark. Once the layer is disturbed, sparks can be cooled in a fraction of a second. The eddies can be created by

abrupt change in duct sizes in the system
single/multiple plates with orifices placed near the hood inlet
change in direction of duct such as a square elbow instead of a smooth turning vane
spark trap

 

[Jim Silva]

...It seems to me if you have so much dust in the air of your shop that it will ignite you are likely to die perhaps first of respiratory failure. But I wouldn't suck sparks or metal filings into my Dust Collector....

I seem to be giving people the mistaken idea that I'm using dust collection AT or NEAR the grinder. That is not what I wrote or intended to infer. My DC is no where near any of my grinders nor would it ever be for just the reasons you state.

I don't have clouds of dust hanging around the shop as DC's take care of that BUT as everyone who's ever cut, sanded or otherwise shaped a piece of wood I do have dust and shavings that accumulate that DC's and air cleaners don't and can't catch. That residual that collects in corners, around benches and on the floor is the very thing I see every grinder sitting in. THAT's what I'm questioning the safety of. I mentioned the DC and grounding of said DC as an example of the degree of caution I treat highly combustible materials with.

As for starting a fire with flint and steel, I've been able to do that all my life (former eagle scout 😀) so I don't see starting fires with small sparks as a challenge. LOL

My question boils down to this. During normal operations, IE: touching up/sharpening on a grinder, do the sparks constitute any fire hazard with dry, dry, dry shavings and dust on surfaces in the vicinity of the grinder.

 

[Joe Greiner]

I wasn't in the Scouts, but I had the impression that Eagle Scouts were not "former." I thought you were stuck with it for life. I'll check this out with one of my neighbors later today.😀

My small shop is a sliding-block puzzle. Almost everything is on wheels, including a rolling cabinet with grinder and lathe tools, usually located near the lathe, but never in a corner where dust accumulates. Maybe I'm overly fastidious, but I clean (sort of) the area near the lathe and grinder after each session, not "several times a week."

Using dull tools isn't very safe, and you might want to consider a second grinder, especially if you use specialized jigs for sharpening. Wheels and extension cords are good investments.

Just my 2 cents added.

 

[steelguy]

Sharpening in shops

Jim - Having spent a 36 year career in the specialty steel production and tooling application business, I am used to sparks from lots of sources and many different types of dust - suspended and otherwise. Evacuation systems on arc furnaces and 300 hp grinders do catch fire, but under extraordinary circumstances which have no resemblance to a home shop. My take on your question goes like this:

Casual wood dust on, under, or near a grinder is not an issue as long as you are simply touching up tool edges. If on the other hand you are doing a large amount of grinding as in changing a square scraper to a bull nose scraper, (or cleaning up a badly dinged lawnmower blade!), simply brush away the dust from the area of spark impact and the immediate area of the grinder. The sparks from grinding cool very rapidly and are not an issue as long as they don't pile up in a >600 degree F pile.

Relative to fire, I am much more concerned about misplaced radiant heaters, halogen lights, and smoker ashes and butts. I also am very careful about closing off dust access to water heaters and furnaces.

Jerry

 

[MichaelMouse]

Back to basics which say fire requires fuel, heat and oxygen. Sawdust is pretty tough to light because it's packed too tight as it accumulates. If you've ever tried to ignite it, you no doubt found it requires a longer application of heat than a casual spark will give. Don't think I'd weld around it, though.

Shavings, on the other hand, make wonderful fire-starters. I store them well away from the furnace, however.

 

[john lucas]

I forgot to tell you. I was using my 3" belt sander turned upside down to make a knife. I forgot to remove the dust collector bag. It did burn a small hole in the bag but no real fire. I would say that's a worse case scenario short of grinding right next to your dust collector.
I burn my dust and wood out back. Dust by itself is very hard to ignite. It just sort of smolders even after I use a butane torch to ignite it. Airborn dust on the other had is dangerous. I once dumped the dust bag on the existing fire. I had a fireball about 5 feet in diameter which partly surrounded me. Fortunately it was extremely brief. I don't believe you'll ever reach that kind of concentrated dust in the shop. Next time I'll yell, Hey Bubba watch this, before I do it. NOT.

 

[Richard Baker]

Sorry I missed that John. But is a good example of the dust concentration and dispersion required for ignition. Worth noting that the ignition source was a burn pile in progress, not just a spark.

 

[Mark Warden]

I had a pretty scary experience with my belt sander after reshaping a gouge.No problem during the actual shaping and sharpening but while I was turning afterward my shop started filling with smoke and I didn't know where it was coming from.Turned out it was the dust inside the belt sander smoldering never actually ignited but did produce allot of smoke.

 

[Bob Boettcher]

I have not had a problem with the grinder, but I did have smoldering shavings fall out of my gooseneck light while I was turning. That was quite a surprise, and a cause of considerable scampering around to ensure there was no fire.

Bob