I’m mad at myself for not thinking some things through that I should have seen coming a mile away.
Grinding metal creates lots of dust – sparks fly everywhere, at all angles, and it’s just unavoidable. Or, is it? Here’s the problem: it needs to be avoided. When I was a kid I didn’t take it particularly seriously but lately I’ve had opportunity to pause and reflect about what kind of stuff I may be breathing in. I mentioned Dan U., who died at 40 of mesothelioma because he was young, and immortal, and didn’t wear a breath mask. Sensei Bell wears a breath mask, now, but he’s got respiration problems from years of breathing in metal dust and forge gases. [stderr]
I’m 55, and I could probably do like Ansel Adams and say “something else will kill me first” but from what I’ve seen of mesothelioma and COPD I don’t think either of those is a particularly great death. I’m holding out for a massive stroke while I’m asleep after watching a great movie, or something like that. I probably won’t get that, but I damn sure don’t want the shortness of breath or cancer.
The problem, in a nutshell
Even if I am wearing a mask, I get home and my hair is full of dust. That’s just a bit of what rinsed off me one time – sometimes I rust after I shower.
I’ve been wearing a small silicone half-mask, but dang that thing is awkward with my face-shield and earmuffs, too. I may as well be wearing a space-helmet. So, I looked for one of those. Alec Steele wears a 3M Powered Air Purifying Respirator (PAPR) which is, pretty much, a space helmet – it’s got a belt-pack that provides filtered air at a steady rate, so you don’t have to suck against the resistance of a filter pack. That extra bit of effort translates into whooping gasps for air when you’re standing in front of a running forge. None of this is good.
Searching around on ebay, I discovered that the head units of the PAPR are relatively cheap – what’s expensive is the batteries. And for some reason, 3M is cagy about the power formula of the batteries. It took me a while to find out that it’s 4.8V DC, 4a – which means that a $2 DC stepdown transformer (12V DC to 5V DC) will allow a USB portable recharger pack ($20 on ebay) to do the same job. I ordered parts and am waiting for everything to arrive and I’ll see if I can make the mask’s air filter pump work without shorting anything out.
Then, there was the other day – I was prepping a stack of victorian wrought iron and something was nagging at the back of my mind. It was the paint. The lovely orange-red paint on the wrought iron. I grew up in Baltimore; I know what lead paint looks like. I had been dancing around in a fountain of lead dust of my own making. Other than the fact that it’s plenty of fun, none of this is good.
A lot of knife-makers like Alec and Haley DeRosiers have “grinding rooms” – a room set up for where you can fire sparks all over the place, and there’s nothing flammable – where the working surfaces are designed for being swept down and swept up. Great idea. It’s much better than my arrangement, which consists of sweeping up tons of dust about every other week.
Right about then was when I sat down, pulled on my engineer’s boots, and started kicking my own ass. There’s something I didn’t mention to you all: attached to the 1st grade classroom (where my shop is) is a door to the Principal’s Office. The Principal’s office has a big old steel-case desk that weighs about 200 pounds, an old IBM selectric typewriter, some rotary dial phones, and other than that… It’s a perfect grinding-room. It’s about 8 feet by 8 feet and has a little closet for storing abrasives, it’s perfect. What’s not perfect is the rest of my shop. If I move the belt sander and angle grinders to the grinding room (which is about right) then my main workbench could be half the size it is, and could be a clean assembly bench not a powder-covered EPA superfund zone. But I built that workbench so thoroughly that the idea of taking it apart feels like satan laughing at me: “you built a nearly indestructible workbench, mortal, and now you have to disassemble it, saw it in half, and re-assemble it.” That means sawing the frame tubes on the bandsaw, but first that means disassembling them. Etc. It’s going to take my shop down for a week, at least, and it’s all my fault for not thinking a little bit harder before I got started building the shop.
In the end, it’s all good news. I’ll put an air filtration system in the upper part of the grinding room, and I am going to build an external feed air pressure filter system. That’s short for “knocking a hole in the wall and running a shop-vacuum hose down from an arm on the ceiling, then setting up the hose on the out-flow of a mini shop-vac with a HEPA filter on a speed control.” It ought to be like a PAPR system except it’ll be bringing in cooler air from another room. We’ll see how it works in practice. Total cost of the components was $30 on ebay and I have them all in my “to do” box in the hall. Did I say “to do box”? It’s a great big phalanx of boxes.
First, I need to build Grinding Bench 2.0, and Grinding Power Cord Management and a shelf for the collection of angle grinders and a hanging rack for the belts and disks and whatnot. Somehow I will hoist a great big Jet air filtration system up to the ceiling, and I’ll put a sheet of plywood over the door to the rest of the building and seal it off so no dust is going under the door. No, wait – that reduces the number of fire exits my shop has by one, which is not good. I think I’ll make a curtain with a weighted bottom. That’ll be a moving blanket tacked to the door frame at the top, with a hem at the bottom full of stuff.
In case you forgot what a godzilla-resistant frame I built under the grinder bench…
Perhaps this will give you some understanding of why I track the F-35 program: I am profoundly sensitive to the consequences of “mission creep”, “feature creep”, “specification creep” and “cost overrun.”
Time to call in a dumpster.
The beeswax finish on the oak plywood of Grinding Bench 1.0 was not so great – hot sparks stuck and clung and burned their way into the wax, refusing to come out. Grinding Bench 2.0 will be covered with a sheet of 20g brushed stainless steel. That should dust right off. Of course it means I’m going to have to figure out how to hammer a lip along the edge of the sheet. I may just haul it to the machinists – they have a bender and I won’t be stuck trying to make a mess of it with an oxyacetylene torch and a hammer.
When I have moved the grinder, I will re-do Grinding Bench 1.0 to be a 4×4 square, which will give me more room at the end near the windows, where I have the bandsaws. It turns out I spend a lot of time working the bandsaws and I don’t like being between the Scylla of a bench covered with hot stuff and sharp things, and the Charybdis of a metal-cutting bandsaw with a raker blade. A few more feet of distance would be comforting.
But honking great globs of black snot into your hankie is traditional, eh wot.
Lofty@#1:
But honking great globs of black snot into your hankie is traditional, eh wot.
I used to do that. Sanding ebony makes for some truly amazing sinus slag.
Good thinking on protection and the sanding room.
If the electronics take 4.8 V batteries, I’m quite certain they will work with 5 V too. So you could use the USB power bank directly. Have you checked that the dropout of the DC-DC converter is low enough to be able to convert 5 V to 4.8 V? The more common types you can buy on eBay as modules start are not ultra-low-dropout types — they need an input voltage at least 1-1.5 V higher than the output.
Or, just use four rechargeable NiMH batteries, C or D* size — that’s probably how they get 4.8 V anyway, because there’s no other combination** of batteries that adds to that.
* The D size rechargeable batteries I have have the exact same rated capacity as the Cs, and weigh only a little more. They’re C-size cells inside D-size shells. (Say that three times fast.)
** Ni-Cd, but it’s not the 1990s anymore.
s/start //
The main risk lead poses is to the developing brain. It’s very bad to expose children to it. You, on the other hand, should probably be OK.. ;)
With regard to your weighted curtain, you could also put velcro up the sides to ‘stick’ them to the wall. Also you could put that stick on foam draft excluder round the door, with a rubber ‘blade’ draft excluder along the bottom of the door. In fact you might want to do both of those to the door into the 1st grade classroom just to make sure as little as possible dust can get back into the rest of the forge before it’s been wooshed outside.
I’ve been reading your blog for a while and was kind of curious just what method of dust collection you had in place. After all, not only is it a health hazard, but with dust flying around in the air and a huge honking forge putting out extreme heat, among other sources, explosion, or even “just” fire would be constantly weighing on my mind.
That said, I do know a thing or 2 about room pressurization. For one thing, everything depends on your cascade: do you just want a room negative to everything around it? Do you want one room positive to one and negative to another? Does your whole shop need to be positively pressurized to the outside?
My advice, and the way I learned to do it in my own work, is to always start with a floor plan and detail how you want the air to flow. From there, you can also decide if you’d prefer to seal entrances and exits, as you’ve detailed here, or you can go another route by installing filtered exhaust in order to maintain negative pressure without ejecting all that material into the environment. Once you’ve established your airflow parameters, doors don’t generally require seals, but if you really wanted to, you could install a sweep on the bottom. At any rate, this system is standard for infection control and works pretty well, so I’d think it would serve a similar result for physical contaminant isolation.
This reminds me i really need to buy a proper respirator. I need these lungs for a while yet
Janstince@#7:
I’ve been reading your blog for a while and was kind of curious just what method of dust collection you had in place. After all, not only is it a health hazard, but with dust flying around in the air and a huge honking forge putting out extreme heat, among other sources, explosion, or even “just” fire would be constantly weighing on my mind.
When I’ve got the forge running, I don’t do any grinding, and vice-versa. Mostly because it’s just too hot and unpleasant and I don’t want anything falling on an electrical cord or anything like that.
I don’t think I need to worry about a dust explosion because iron and steel have a pretty high kindling temperature. The whole building would catch fire before it got hot enough for the dust to ignite. That’s my reasoning, anyway.
As far as the pressure map, I’m going to just seal the grinding room and recirculate it, though I may open the windows if it’s a nice day. What I was thinking in terms of “positive pressure” is in the breath mask itself. The small half-face masks (like I am using now) you have to suck the air in through the filters, which takes a surprising amount of effort when you’re hot and sweating. The PAPR masks provide a slow wave of filtered air all the time, so you just breathe normally, no sucking. I’ll experiment with getting the battery pack working so I can run the PAPR mask and I’ll also experiment with a ceiling-mounted breath hose – both of which would provide a steady bubble of filtered air into the mask so I wouldn’t need to labor to breathe.
I am also going to build some kind of catch-bin under the grinder, to collect the dust that shoots straight down. That’ll also mean 1) less cleanup 2) less airborne dust 3) less rust 4) fewer sparks trying to set my socks on fire
I see. You’re not as concerned about the dust spreading to other parts of the shop because the particles are much heavier than, say, bacteria, spores, and viruses. I hadn’t really thought about that aspect.
As far as ignition temperatures, I understand that your forge runs below that temperature in general, but sparks from grinding don’t necessarily, and an electrical failure can throw all bets right out the window. On that note, would you recommend grounding the metal of your grinding table frame to prevent a short in your circuitry from arcing into the space, or a significant buildup of static? I suppose it depends on the floor surface material.
As far as air recirculating goes, I would recommend some method of bringing in fresh air. I know, the human body can handle a couple orders of magnitude of CO2 higher than in present atmosphere readings, but that is not without significant side effects. Sailors in submarines generally tolerate around 2,000 ppm in concentration, but most building A/C systems are designed to keep occupied areas below 1,000. Some studies have shown that cognition begins to drop even as low as 800 ppm. Not only that, but there are other, possibly more dangerous, contaminants in the air, particularly in buildings, that your have to watch out for. If the building isn’t sealed well, it’s not as big an issue, but if you are surrounded by concrete, forced fresh air infusion is the best method. Basically, if you’re going to seal a room, you need to make sure you’ll have enough air in the room to last you as long as you stay.
I guess you’ve already considered this. You’re very thorough in your planning. One of the reasons I like reading this blog. It’s just that my profession always leaks in to these kinds of discussions, and most people don’t have to give a first thought when it comes to buildings and all of the wonderful things they provide which can suddenly turn on you like a rabid mongoose if you don’t think about them.
Janstince@#10:
When you’re pushing 10psi of propane through burner jets, you’re probably burning through the oxygen in a typical room in a couple of minutes. I don’t know how much of it’s CO2 and how much is CO, but I’ve got CO warning alarms at head height and ankle height. By the way, here’s another fun fact: what is a high carbon steel blade made of? Why carbon and iron, of course! So as you heat it, the ‘scale’ that you see flaking off is decarborized steel. The rest of the metal leaves in the form of CO2. For something like a sword, where you’re going to work on it a lot and do multiple weld passes, you start out with a chunk of steel about the size of 3 packs of cigarettes stacked on top of each other. And you end up with something about half that size, just from the metal evaporating.
There are big windows in the studio and in the grinding room, and I flip them full open and have an exhaust fan (one of those big barn fans!) at the other end of the building. That makes sure there is a nice tractable breeze. I don’t want a great big gusty wind – you know, the kind that blows sparks? Just a nice tractable, regular, predictable breeze.
You’re very thorough in your planning
Computer security is the art of looking at all the things that can go wrong in a situation, and hedging off as many as you can. I’ve been very good at that, all my life. So far, so good. There are a few things that I overlooked and figured out before something went horribly wrong, so that’s – so far, so good. I’ve learned things like “spark check” you know, don’t direct a stream of sparks toward your oxy/acetylene gear? So you think “what if my machine grabs this work-piece and throws it? where will it go?” and you stand to the side of the grinder and wear kevlar chaps. And you take the kevlar chaps off before you use the bandsaw because that could go horribly wrong in a different way.
My feeling is that (this is because I am a computer security guy) life is an endless sequence of chances to make horrible mistakes. All the time. People fall in the shower, hit their head, and die. When I wrote my book on homeland security, that was a thing I learned: you’re more likely to die in a bathtub accident than a terrorist incident, by nearly 10:1. People get on the freeway and drive around not realizing that the trucker in the semi behind them hasn’t slept well in 2 days. Or, in Pennsylvania, they ride motorcycles and don’t wear a helmet. All these things are edge play – you’re risking your life. Working with a blade forge is also edge play. I’d rate it as safer than skydiving or certainly BASE jumping. My friend Michael H. was one of the early innovators in hang gliding, (if any of you are hang gliders, I’m referring to Pelican H.) he told me once that of the group he started with, half of them are dead. I haven’t even heard of a knife-maker who’s died at the forge – and there are more knife-makers.
I won’t let my guard down. I have a rule I follow when I use a table saw: tired? No power tools. If I get tired forging, I turn it off, put everything up to anneal and I can pick it back up later.
You’re not as concerned about the dust spreading to other parts of the shop because the particles are much heavier than, say, bacteria, spores, and viruses. I hadn’t really thought about that aspect.
Right – that’s why I was worried about carbon fiber. That stuff floats like spider silk. Totally changes the equation. And as lorn mentioned in my posting about carbon fiber – the stuff is conductive and it can do odd things. [stderr] What if I grind CF dust and it floats into the exhaust of the forge, gets heated to red hot, and blows right in my face? I get to make a lot of simplifying assumptions because metal dust is pretty heavy. By the way, aluminum – that’s a whole lot more combustible. I won’t grind that stuff, ever, nohow. File and milling machine, OK. (Aluminum powder and potassium perchlorate is the guts of an M-80)
On that note, would you recommend grounding the metal of your grinding table frame to prevent a short in your circuitry from arcing into the space, or a significant buildup of static? I suppose it depends on the floor surface material.
I will ground it, now. Hadn’t occurred to me. Thanks! Some of the belts we use are basically leather soaked in jeweler’s rouge (red iron oxide) – look, ma, it’s a van de graaf generator!
jazzlet@#6:
With regard to your weighted curtain, you could also put velcro up the sides to ‘stick’ them to the wall.
Perfect! And, as material for another project, I have several 100 foot rolls of velcro on my sewing knicknack shelf. (the head-liner for my step-van was velcro’d in so I could throw the red flocked velveteen into the washer if I needed to..)
Yeah, aluminum. I didn’t know it was so dangerous until that explosion in the iPad plant in China. After that, I did some reading on the stuff. It would be doubly bad for you, having a bunch of rusty iron dust around and adding aluminum dust to it. Kind of a “hold my beer and watch this,” homemade thermite video on YouTube.
The problem with HEPA filtration is that you have to maintain face velocity across the surface or it doesn’t work. Standard filtration, you could increase surface area and decrease the face velocity, which would result in a decrease of pressure drop across the filter and reduce the suction required to pull the same amount of air. For HEPA filters, the idea is that you maintain a higher face velocity and the filter, even with “holes” that are larger than a standard filter’s, are able to attract and trap the particles more effectively by using induced turbulence in the airstream. Great for constant forced airflow, not so good for lungs.
I forgot about the carbon combustion from high carbon steel, or the steel evaporation itself. Materials science is about a decade behind me, now. I vaguely remember some things about composition and quenching rates, but not anything I’d trust my memory to. I really like this blog for a refresher about the science behind blacksmithing; I’ve always found it fascinating but never had the space or money to get into metalwork, be it machining, welding, or smithing, other than a brief stint in the workshop in college and a bit of engine work in a mechanic shop during high school.
As a side note, do you know any blacksmiths that use induction forging? I checked that out a while back, seems like an extremely time and energy efficient method. Not so sure how well it works on anything other than steel, I’ll have to read up on that.
Janstice@#13:
As a side note, do you know any blacksmiths that use induction forging? I checked that out a while back, seems like an extremely time and energy efficient method. Not so sure how well it works on anything other than steel, I’ll have to read up on that.
It works on anything metallic.
If you want to see something truly terrifying you can look at this item: [ebay“] Why not use your home microwave as an induction furnace? Just don’t spill molten metal on your kitchen floor.
There are makers who use induction heat. Bob Kramer has an induction unit he uses to melt bolsters and pommels, etc. [youtube]
I know there has been discussion about using induction heat in controlled gas chambers, to prevent oxidation. That allows some pretty crazy welding (since most welding problems involve keeping oxygen off the surfaces) such as titanium damascus. Timascus has been done – I happen to think it is ugly as 1 week old pizza – but there are people who like it. I believe the idea is that you make a stack billet similar to how you do mokume, then put it in a crucible that has the oxygen replaced with argon or something like that. Heat it up until it starts to puddle-weld. It’s a process similar to how wootz steel is made.
All these things are terrifying because they involve working with thermal masses and moving them around. If your crucible tongs slip, you’re dead. If your crucible cracks, you’re dead. If you mis-pour, you’re dead. Most of the failure modes involve you catching fire and since it’s thermal mass igniting you, you keep re-igniting until it cools enough. A fire extinguisher will not help. There’s footage of Neils Provos lifting crucible steel out of his furnace, and he’s up on a ladder (avoiding splash) but it’s an aluminum ladder – if the metal splashed it’d melt the leg off and he’d wind up falling on some direction. I still get the eebie jeebies when I watch that. (Solution: let it melt in the crucible, and let it cool in the crucible – don’t move it at all) If you want to see really scary stuff google up Japanese swordsmiths working a “tatara” – it’s how they extract iron from iron sands, and it involves molten iron running out of the smelter like honey. Nope, nope, nope!
PS –
Kind of a “hold my beer and watch this,” homemade thermite video on YouTube.
Thermite is highly overrated unless you’re using a 5 gal bucket of the stuff. Then it gets interesting. Thermic lances are also somewhat overrated. But you can destroy the world if you have an angle grinder and a couple of diamond cut-off wheels. I always get furious when I see movies (Breaking Bad I am looking at you!) where someone uses thermite to cut a lock. A diamond blade in a coping saw is way better, it goes through chain like it’s cheese. Although I will say, a railroad bucket of thermite would provide a great “fix” for some of the confederate statues. Just use some chains to attach it to the torso long enough for it to get hot, light it, and then be somewhere else.