Hobby Workshop Safety Part One By James Goss      If you like to build models like I do then you probably have an area around your house designated as your workshop. This could be an unused room in your house such as a bedroom, dining room, garage, basement or an exterior building outside your home. Wherever you have your building area located I am sure you spend a lot of time there like I do. When it comes to shop safety we have to really be careful in our line of work because of the type work we are doing. Trying to build tiny little parts like we are involved with can actually be just as dangerous as fabricating large industrial devices. This may sound odd to you but I have personally seen several bad accidents take place. These accidents were a result of someone trying to fabricate a tiny little part from wood while operating large woodworking machinery. Fingers severed because tiny parts require that you hold them close to the saw while cutting to shape. I have seen table saws propel small sharp pieces of wood that got pinched between the saw blade and fence, across the room like a bullet. Breaking windows and hitting bystanders, these projectiles could be deadly. There are ways to prevent these accidents from happening and I feel it is good to talk about them from time to time so we will stay on our guard. If you have ever had an accident around your shop or have seen one take place or have simply heard about one, send in the details to me and we will talk about it in the newsletter.     What I would like to talk about today deals with electrical safety around the shop. I can guarantee you that the number one electrical safety problem around most shops will be related to electrical grounding first and then improper equipment being used in place of what is called for as a second most serious hazard. The theory of grounding is not hard to understand and is probably the most misunderstood part of any electrical installation. If you have two objects that have the same electrical potential on them it is safe to say that there will be no current flow between them. This is what equipment grounding does; it prevents the chassis of a device, such as a metal power tool, from becoming electrically hot if a fault occurs in that tool. If the metal chassis of a tool you are using becomes hot, because of a fault in the electric motor, and you are standing on a floor that is an electrical conductor, such as damp concrete, your body will be exposed to 120 volts ac. The actual amount of voltage will depend on how good of a ground you make contact with. 120 volts ac is a lethal voltage! More people are killed each year with 120 volts ac than any other voltage.     If you are holding the faulty hand tool and touch another metal case tool that is earth grounded you will receive the full 120 volts and could easily be electrocuted. One side of the ac line is earth grounded and is called the neutral conductor. It is also referred to as the grounded conductor. This is where the confusion comes in; the grounded conductor is not the grounding conductor. The grounding conductor (ing), also called the equipment ground, is the bare or green conductor in a cable or conduit. It connects to the metal chassis of tools and appliances so that if a fault does occur in that piece of equipment and a hot wire touches the chassis, a short circuit will occur and a breaker will trip. The idea here is that it is better to shut off the branch circuit than to have a hot chassis just waiting for someone to touch it and get electrocuted. So let me say again that if a fault occurs in an appliance or hand tool and the hot wire touches the chassis or frame, the branch breaker will trip only if the frame of the device is earth grounded. If the frame is not grounded it is said to be floating and can carry the full potential of the hot wire. There is nothing more dangerous than to have a hot chassis on an appliance of hand tool in an environment where there is a lot of other grounded devices nearby. Over the years I have checked hundreds of electrical systems that had improper grounds through out the building. A large portion of these cases were brought to my attention because someone was receiving and electrical shock and wanted me to find out why.      The receptacles in your home or shop are required to be of the equipment grounding type. That is to say that the receptacles are a three wire two pole device. If your receptacles are in a metal box, and older systems will be, then the box must also be grounded as well as the receptacle. It is not by code standards to ground the box only and depend on the screws that hold the receptacle in the box to bring a ground from the box to the receptacle. The reason for this requirement is that if the screws become loose the receptacle would not have a solid ground. Even though this is a code violation you will find this still being done. If the receptacle has a self grounding strap that holds one of the two 6-32 screws, then it is excepted, of if you have metal to metal contact between the receptacle and metal box then it is also excepted, but this is rarely the case. The best way is to have the grounding wire bonded to the box and also bonded to the receptacle ground terminal.     To check your receptacle for proper grounding is simple. Have someone that is experienced with measuring ac voltage to make these simple tests. Set the voltmeter for ac voltage and select a range that will be equal to or higher than the 120 volts. The face of your receptacle has two vertical slots and one half circle. One of the slots will be longer than the other slot and this is the neutral slot. The shorter slot is the hot side of the receptacle. The half round circle is the ground prong. Place the meter probe into the hot slot and the other probe into the ground prong. If the receptacle is grounded properly the meter will read 120 volts. Next place the meter probes between the neutral slot and the ground prong; the meter should read zero volts and not 120 volts. If you read zero on the first test and 120 volts on the second test, the receptacle is wired backwards. That is to say that the hot and neutral conductors are crossed.  This can be a very dangerous situation and needs to be corrected as soon as possible.     120 volts is a nominal voltage rating and your home or shop may vary from this value. It should be in the range of 110 to 125 volts, this is not that critical. You can buy a small receptacle tester for about $5 at Lowes that you can plug into the receptacle and it checks all three voltages at the same time by having three combinations of lights to be on or off as an indicator. This little device is well worth the money and it allows you to test your receptacles fast and easy. You should at least check your receptacles two times a year to spot a hazard before it happens. Next newsletter in shop safety I would like to discuss GFCI protection and also some good facts about using extension cords in your shop. Remember, when installing an electrical system to first make it safe and then make it work. It is easy to wire up some lights and receptacles and get the lights to come on when you flip the switch and have the receptacles furnish 120 volts, but it requires a little more effort to make it safe when faults in the system occur.