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Up Topic Welding Industry / General Welding Discussion / Wooden Welding Table???
- - By amalgam (*) Date 04-19-2003 04:53
Hi there,
I am starting in this hobby of welding. As of right now, the only space available to me is my garage. however, later on I am going to have a special place for my junk. Therefore, I do not want to build any definitive structure until I have the new space available. Right now, I have a perfect wooden workbench, and I planing to change the wooden top for a strong metal one. I read on the Lincoln Electric website that to weld on wooden surface present a "real fire and electrical shock hazard" I understand the fire hazard but WHY DOES IT REPRESENT AN ELECTRICAL SHOCK PROBLEM? I have seen the videos on the Weekend Welder website and the guy welds a whole rail on top of a wooden surface. Please, can any expert out there tell me if I can go ahead and use my workbench with a metal top as a welding table. I promise that I will not create any fire, but I am afraid about the electrical shock situation.
Thank you
Parent - - By CHGuilford (****) Date 04-19-2003 14:38
I don't understand the electric shock hazard with wooden surfaces either. Metal surfaces are certainly more conductive the wet wood will be. Maybe they generally meant to be careful in all aspect of the welding?
The fire hazard is very real though, with or without a wooden bench. It is good to remember that sparks can roll all over the place, even into corners a long way from the actual welding, and where something can smoulder for many hours without being noticed. That's why a firewatch must stay on the work scene for at least an hour after welding stops.

Remember that heat travels through metal and could burn your bench under the working surface. If you go that route, just don't go to bed until you know for sure that all is OK.
I too have welded with my parts on a wood surface. In my case, I used a piece of plywood across two saw horses. Everything was done outdoors so I knew nothing else could burn.
CHGuilford
Parent - - By Dirtrider (**) Date 04-19-2003 17:26
Ya, if your bench is built-in against a wall you'll need to be more carefull, sparks will fly and find their way into some dangerous places. If you can pull it out and isolate it in the middle of the garage would be better. I've been using a large Workmate bench with a peice of plate on top for smaller stuff. Other than that I weld on the concrete floor. I've seen some of the same stuff where guys are welding up tube frames on wooden jigs. I believe the wet the areas down some around the joints to be welded though.
Parent - - By amalgam (*) Date 04-21-2003 04:32
Hey Dirtrider,
I saw your profile and read that one of your hobbies is to mess around the garage. One quick question, If I isolate the table in the middle of the garage as you said. How far can the sparks go before they cool down? I tend to be extreme when I deal with hazardous situations, but frankly after reading a lot about the subject I am almost paranoic about one spark burning down my house. Any experience, idea, or anything that you want to share with me.
Thank you so much
Parent - By Arcandflash (**) Date 04-21-2003 15:25
I do all my welding a bit outside the open garage door and I make sure the immediate area inside the door is free of combustible material. I avoid welding inside the garage for two reasons; fire hazard and noxious fume hazards from welding. The fumes are a real problem unless you have adequate ventilation or always wear a respirator.

Normal sparks from electric welding probably are cool within 3 or 4 feet but that's what the statistics say. It only takes one bigger spark to start a fire. You can reduce the problem by temporarily enclosing your work area in the center of the garage with a fireproof material. These walls should extend above the level of the weld. If you are using gas torches then get outside especially if cutting.

Practically speaking, if you have a clean, uncluttered garage with no combustible material nearby you probably have little chance of fire with electric. However, little chance is definitely not zero chance!!!

Bill
Parent - By amalgam (*) Date 04-21-2003 04:35
Thank you CHGuilford For answer me
Parent - - By Arcandflash (**) Date 04-19-2003 23:41
I wonder if they assume that a metal bench would be grounded and therefore would be safer. Since the output connections of many (some, all??) welders are floating (at least my stick welder is) then it could be possible with a bit of leakage caused by poor insulation in the transformer to create a voltage on the secondary with respect to ground. It would be possible to raise it to the line voltage but it would be a high-impedance source and would not likely be a severe shock hazard. When you put the so-called ground lead on a workpiece on a grounded table this would remove the voltage caused by leakage.

I have a metal table but it is on rubber wheels so I guess I lose too if my rationale is correct.

FWIW,
Bill

Parent - - By amalgam (*) Date 04-21-2003 04:36
Bill, Thank you so much for answering back
Parent - By Dirtrider (**) Date 04-21-2003 16:52
No reason to be overly paranoid, but be cautious and aware of how much of a radius your sparking. I am by no means an experience welder, but am learning too. As mentioned above, just keep things tidy and swept up. I do a lot of woodworking too and saw dust will go up quick. Personally I think grinding and cutting with an angle grinder is more of a fire hazard, but again if done in the right place....outside, it's fine. I prefer to weld in the garage, with the door up, so the wind and draft isn't too bad that it effects the argon and your weld.
Parent - - By 49DegreesNorth (**) Date 04-21-2003 21:05

I have been using a wooden table with a piece of steel on it for some time. Yes, the shock hazard comes in because the table itself is insulated -- just like the table on rubber wheels. If you forget to clamp the grounding wire to the table, as I have done, you can get a shock because you can become the best route to ground.

That said, Lincoln is just covering their butts, really. A wooden table with a piece of steel on it is fine. Or if you're doing big work you can clamp the ground to the work and do it on any surface that won't burst into flames.
Parent - - By Dirtrider (**) Date 04-22-2003 02:17
"do it on any surface that won't burst into flames"

Damn, there goes my Ratan welding table idea. :(
Parent - - By jwright650 (*****) Date 04-22-2003 12:38
Bill,
I was thinking along the lines you were as far as the metal table being grounded. I like to clamp the table leg and the part will get grounded by laying on the table. We deal with heavy items and ground is not a problem. Holding a piece with your glove (to tack it on) could get you jolted if you start welding on the piece you are holding rather than starting on the piece that is grounded.(been there dundat:) Wet wood could possibly give you a concern for shock, but so would a wet steel table. Also keep your boots dry(I've felt the tingle in my shoes when it was hot and my socks were soaked from sweating). Common sense is good to use and will head off alot of possible problems.
Be careful,
John Wright
Parent - - By Arcandflash (**) Date 04-22-2003 15:09
John,
I have a stick welder so I don't know if what I am saying applies to MIG and TIG machines and perhaps even all stick welders. I was thinking of the grounded bench as being a real ground. Often the workpiece clamp is referred to as the ground but it may actually be floating with respect to a real earth ground and a measurement between it and the earth ground should still be zero. The input AC power however is indeed referenced to a real earth ground and if the insulation is a bit weak inside the welder such that the secondary circuit gets "connected to" the input voltage via the weak insulation then the welding cables with respect to earth ground can become hot.

Clamping the workpiece clamp to a grounded metal bench would drain off this voltage. Since the leakage path would unlikely be a dead short it wouldn't cause any breakers to trip. In fact the leakage current would likely be very small. However, if there was a dead short due to severely failed insulation then the grounded bench would cause the breaker to trip and protect the weldor, not to mention, scaring the hell out of him/her. This would not happen with a wooden or ungrounded bench.

Of course, I don't know if this is really why Lincoln said use a metal bench. Nice theory though.

I have learned from this thread in that I never thought of the possibility of getting a bit of a shock as you have described by holding the workpiece.

Bill

Parent - By amalgam (*) Date 04-22-2003 16:40
Bill,
You mentioned in your message a grounded bench. What is a grounded bench? A company is going to install a 230 volts outlet in my house so I can use my MIG welder. Is there any thing that they can do for me to ground my bench.
Alfredo
Parent - - By amalgam (*) Date 04-22-2003 16:33
John,
You brought a very interesting point to this discussion. When I was learning welding, I held the piece with my hand (with gloves of course) to tack it on and neither got jolted nor the teacher told me anything about any danger in doing this. I am going to start doing metal sculptures and many of my pieces are going to be light, thin, and small. Therefore, I think I will be clamping the table instead of the piece. Will I be in danger? Should I keep my body away from the table and piece? Metal art is a passion that I have and I want to do it having fun instead of feeling that I have my life on the edge of a nife any time a press the trigger.
Alfredo Alamo
Parent - - By jwright650 (*****) Date 04-22-2003 16:48
Alfredo Alamo,
You probably, without realizing it, started the arc over on the work piece that was grounded, and by tacking it, grounded the piece that you were holding. That is how it should be done. I was referring to FCAW (same principle) and pulling the trigger with the wire over on the piece I was holding rather than on the work piece that was grounded. It let me know I goofed up. I haven't experience the high frequency GTAW starts that can bite pretty good, but I hear it makes you sit up and notice. All I was saying, is to initiate your arc on the grounded side of your work when tacking on a piece that YOU are holding in place in lieu of clamping.
John Wright
PS. If you want some interesting warnings to read, check out the post about wet welding and scroll way down to a link to the navy's underwater welding procedures. Original poster Len Anderson ( Oh Len are you still out there? )You'll get that after you look up the link
http://aws.org/cgi-bin/mwf/topic_show.pl?id=3179
Parent - By jwright650 (*****) Date 04-22-2003 16:53
http://www.supsalv.org/pdf/cut_weld.pdf
Here is the direct link, but look up the other post I mentioned as there is reference to the subject you are concerned about.
John Wright
Parent - - By amalgam (*) Date 04-22-2003 17:36
John,
I am very new at welding so let me see if I can define "grounding"
1) If I put the clamp on the table, then the table is grounded, isn't it?
2) if I put a metal plate on that table, then that metal plate is also grounded isn't it?
3) Now, if I hold with my hands, lets say, a metal rod on top of the metal plate that is on the table then Is the metal rod grounded?
So, should I assume that if the clamp is attached to the table anything touching that table is grounded? And as long as the clamp is attached to the table and I am "dry" I can touch any part of the table while welding without deadly consequences? I am sorry about the way I worded the question, but I want to be sure what I am doing before I even plug the machine.
Thank you
Alfredo
Parent - - By jwright650 (*****) Date 04-22-2003 18:04
Alfredo,
Let me see if I can clarify my conditions here in our shop and maybe you will see how things can be set up. First, our "tables" are built out of sections of Wide Flange beams and look like saw horses(not wood). They have the ground (clamp) lead bolted to the legs which are electrically grounded(earth ground) to the columns in the building. Anything we place on these tables, we can then pick up the FCAW gun or SMAW holder and start welding on without any fear of being shocked, unless as I said before starting the arc on the piece I had in my hand making me the path of least resistance to ground, or wet gloves/shoes etc...
Do you see a little more about what I was trying to say with all that story before?
John Wright
Parent - By jwright650 (*****) Date 04-22-2003 18:43
My reply to question #3 is to initiate your arc onto the piece that is grounded first and at the same time tack your joint and you will be fine. I don't want you to throw caution to the wind, but don't be afraid of welding. It's hot, slatter falls down your collar and pops in your ears, slag will find it's way onto your forearms, neck, lip, all sorts of soft skin and stick before you can get it brushed off. And you might even get a jolt by being part of the welding circuit sometime. Just practice and get comfortable with the process you will be using and you'll be fine. Lots of arc time is good for your ability and technique. As with learning new things, you will learn what to do and not do in time.
Parent - By Arcandflash (**) Date 04-22-2003 18:14
A grounded bench would be one that is electrically bonded to an electrical ground. Your electrical service panel is bonded to ground either through a town water system or a ground rod if you are in the country. This is often referred to as the safety ground.

You can ground your bench by connecting it to your electrical panel or other known grounded structure. You would want a ground lead equal to the ground wire in your AC supply to the welder.

Your welder, as I mentioned in my other posts, may or may not have the workpiece clamp lead connected to ground. You should be able to determine if it is by looking at your manual, the circuit diagram or measuring it to the case of the welder with an ohmmeter. It should be zero ohms. If the workpiece clamp is connected to the case of the welder then it will provide a real ground.

You might want to check your welding machines manual to see if they have any information on this topic.

Bill

Parent - - By TimGary (****) Date 04-22-2003 21:33
Alfredo,
You're getting a lot of good advice here. I thought I might add a little clarification about being "shocked" while welding.
If you weld, then yes, sooner or later you will get "shocked". Over time, you will probably get "shocked" many times.
95% of these times the "shock" will only be a little tingle that is just letting you know that your gloves have become damp, or your sweaty bare skin is touching the metal somewhere. This is not harmful, only annoying.
4.998% of the time you'll get a good shock that is telling you you're really doing something wrong like trying to use soaking wet gloves or standing in water while leaning against the metal with wet clothes on. These kind of shocks will get your attention quick through sharp pain, making your body hair stand on end, leaving a smoky taste in your mouth, and causing you to jump around for a minute while cussing like a sailor, but they don't kill you. Most people take this as a strong warning to fix what's wrong before going any further. If you don't, then yes, you may get in a seriously harmful situation.
Now for the other .002%.
I have to leave .001% for stupid people like me who grab both the positive and negative lugs on a running stick welder at the same time, with bare hands. That SHOCK didn’t kill me, or even hospitalize me, but I can assure you that I'll NEVER do that again.
The last .001% is for people who actually get fatally electrocuted while welding. Personally. I've worked with thousands of welders and in a few very dangerous shipyards and never had a welder die of electrocution from welding equipment. I'm not saying that it hasn't happened, it's just very rare. The only welder's that I've even heard about being fatally electrocuted while welding is underwater welders.
Anyway, my main point is that yes, you always need to be careful and yes, you need to make sure that your metal is well grounded, but you don't need to worry much about being seriously injured through being "shocked" while welding if you take the most basic of safety precautions.
There are better things to worry about like catching yourself on fire, asphyxiation, exploding gas bottles, and crushing injuries from heavy metal.
You'll find that a little common sense will go a long way.
Good Luck!
Tim
Parent - - By amalgam (*) Date 04-23-2003 01:40
Hi Tim,
Thank you for coming in. You are absolutely right I have been getting a lot of good advice and I really appreciate that. As I said in another message, you guys are awesome. Thank you so much for your help, I think that you really perceived my panic. The statistics that you present have taken a big burden off my shoulders and the humor in your message is refreshing. However, one quick question I have heard a lot about "well grounded metal" can you please define that, What do I need to do to get a metal "well grounded"?
Thanks
Alfredo
Parent - - By TimGary (****) Date 04-23-2003 12:27
There are two cables or leads coming from your welding machine. One is the "work " lead and is used to supply power to the electrode. The other is the "ground" lead. You have to attach the ground lead to the metal your welding on, in some fashion, in order to complete the electrical circuit. If you don't have the ground connected, you can't strike an arc, because the circuit isn't completed. If your ground is connected, but for any reason is not making good contact with the metal, then the welding arc will be detrimentally affected because the circuit is not totally completed. Think about it like a kink in a garden hose, you still get water, but not as much as an un-kinked hose. Additionally if you have an uncompleted circuit, the "left over" current is looking for some place to go. If you were to grab the metal with bare sweaty skin with one hand, and then grab the bare end of the ground lead with the other hand, while your friend was welding on the metal, then your body would become part of the ground, and get shocked. If you had a well connected ground to start with, you probably wouldn't get shocked at all, or only very little.
By well connected, we mean that your ground cable should either have cam-lock twist connectors on the ends or securely fastened cable lugs with a bolthole. Make sure the connection at the machine is good and tight, with clean metal-to-metal contact. On the other end, either bolt the cable lug to your work, or attach a spring activated ground clamp. If you use a spring clamp, make sure it is firmly attached to the ground lead and is firmly clamped to the metal. If there is a bad connection on the ground lead somewhere, while welding, it will develop resistance and heat up. That means that if your ground clamp is too hot to touch, or the insulation is melting off the lead, you've got a bad connection and need to fix it.
Try this, run a piece of metal down your wood table leg from the floor to the metal tabletop. Weld the connection at the tabletop and weld a 1/2" bolt to the metal at the bottom of the table leg. Now you have a place to securely bolt your ground lead, effectively grounding your worktable, in a manner that allows the ground lead to lie flat on the floor, thus reducing a tripping hazard. Now if the metal you’re welding is touching the table top, it's grounded, and you can weld on it. Sometimes you'll want to apply a separate ground for better contact, and/or to keep your work from getting marked up where it grounds to the table, so attach a separate, short ground lead to the table top with a bolted connection, and a spring clamp on the other end to attach to the work. Now you're doubly grounded.
Does that answer your questions?
Good luck!
Tim
Parent - - By amalgam (*) Date 04-23-2003 20:57
Yes Sir, that was a brilliant explanation. Just one small detail, what type of mark can a metal get at the point where it is grounded? Also, in my situation I will not have the tripping hazard, so I will be able to bolt my ground lead directly to the table top. In that case can I still run the short ground lead from another point on the table top to the piece to be doubly grounded? Does this short ground lead have to have the same specifications of the main one?
Thank you so much Tim, and I hope I am not abusing your willigness to teach.
Alfredo
Parent - By jwright650 (*****) Date 04-24-2003 11:04
Sometimes you will get small burn marks where the part is getting it's ground from the table if the part is not laying good and flat. The damage will be minimal if the part has flat areas to lay on. A sharp pointed corner or something might get marked up more than a large flat area. The part is trying to get ground from the table and might arc a little where it is making contact until a good ground is acheived. Attaching a ground (clamp ) to the part directly will help where the piece doesn't want to lay flat on the table. Heavy parts will naturally ground better than lighter ones when parts are just laying on the table.
You'll see once you get in there and start on your projects.
John Wright
Parent - By TimGary (****) Date 04-24-2003 11:33
John explained the burn marks well. It's like the mark left when you are unsuccessfully trying to start a stick electrode and it sticks to the metal. (Maybe that's why they call it stick welding?) The marks can be cleaned off by grinding/sanding, but sometimes when you want the finish to be perfect, without a single blemish, then you need to take extra steps to avoid the marks.
If you're welding something that is grounded to the table top, your spare, short lead can be smaller that the ground lead from the welder. About 1/2 the size should do. However, if you want to use this same lead to ground some metal away from the table, it would need to be full size.
Tim
- - By Christos Date 02-16-2021 00:23
Hello. im pretty new with welding. any tips for starters???:roll: i really enjoy the chemistry between me and the machine. i just bought my first welding machine and it immediately clicked. now that we have this subject how does wood welding work??:roll: thanks in advance. kind regards

christos from greece.:wink:
Parent - - By 803056 (*****) Date 02-16-2021 15:56
We use glue in the US.

Al
Parent - - By Jim Hughes (***) Date 02-17-2021 23:12
Maybe you can give him the UNS number so he can find it easier. :wink:
Parent - - By 803056 (*****) Date 02-19-2021 00:16
That might help.

I believe we have a failure to communicate because I am not sure I understand exactly what this young man is asking us.

I applaud Christos for writing to us. He does a better job of writing in English than I can write in Greek. Maybe if he says it a little differently, I will know what he's trying to ask us. I don't mean to offend him.

Al
Parent - By mcostello (**) Date 02-20-2021 03:33
Maybe He is the victim of a practical joke and does not know it. We buy the super premium White Oak rod around here.:lol:
Up Topic Welding Industry / General Welding Discussion / Wooden Welding Table???

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