electric_bending_iron

8/7/2019 ELECTRIC_BENDING_IRON

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ELECTRIC BENDING IRONELECTRIC BENDING IRONELECTRIC BENDING IRONELECTRIC BENDING IRON

This is intended as a short pictorial essay on theconstruction of an electrical side bending iron. As theitems used may vary from the ones shown here, only limiteddimensions are used.

This device is primarily used for bending the wood sides ofmusical instruments. Other uses may be appropriate, but arenot specifically covered here.

WarningWarningWarningWarning This project uses components that generateThis project uses components that generateThis project uses components that generateThis project uses components that generatefreakishly large quantities of heat, and is powered by 120freakishly large quantities of heat, and is powered by 120freakishly large quantities of heat, and is powered by 120freakishly large quantities of heat, and is powered by 120volt AC current. If you are not cvolt AC current. If you are not cvolt AC current. If you are not cvolt AC current. If you are not comfortable working withomfortable working withomfortable working withomfortable working withpotentially dangerous circuits, this may not be the projectpotentially dangerous circuits, this may not be the projectpotentially dangerous circuits, this may not be the projectpotentially dangerous circuits, this may not be the projectfor you. Due to the nature of the high heat that thisfor you. Due to the nature of the high heat that thisfor you. Due to the nature of the high heat that thisfor you. Due to the nature of the high heat that this

project generates, it may not be possible to prevent accessproject generates, it may not be possible to prevent accessproject generates, it may not be possible to prevent accessproject generates, it may not be possible to prevent accessto dangerous areas where exposed wiring might be contactedto dangerous areas where exposed wiring might be contactedto dangerous areas where exposed wiring might be contactedto dangerous areas where exposed wiring might be contacted....

If you choose to build this bender, the responsibility forIf you choose to build this bender, the responsibility forIf you choose to build this bender, the responsibility forIf you choose to build this bender, the responsibility forsafe construction and usage is YOURS. Neither the authorsafe construction and usage is YOURS. Neither the authorsafe construction and usage is YOURS. Neither the authorsafe construction and usage is YOURS. Neither the authornor the site where you obtained this outline accept anynor the site where you obtained this outline accept anynor the site where you obtained this outline accept anynor the site where you obtained this outline accept anyliability for anything unfortunate that may occur.liability for anything unfortunate that may occur.liability for anything unfortunate that may occur.liability for anything unfortunate that may occur. NEVERNEVERNEVERNEVERLEAVE THIS DEVICE UNATTELEAVE THIS DEVICE UNATTELEAVE THIS DEVICE UNATTELEAVE THIS DEVICE UNATTENDED WHILE PLUGGED IN AND ACTIVE.NDED WHILE PLUGGED IN AND ACTIVE.NDED WHILE PLUGGED IN AND ACTIVE.NDED WHILE PLUGGED IN AND ACTIVE.


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A Rough List of items used:A Rough List of items used:A Rough List of items used:A Rough List of items used:

1 - halogen lamp socket

1 - bulb to fit halogen lamp socket (300 Watt)

A 500 watt bulb may be used, but mustmustmustmust be used at alower setting once the desired heat is reached toprevent overheating.

1 - 2 NPT pipe flange

1 10 12 length Rigid Aluminum Electrical ConduitRigid Aluminum Electrical ConduitRigid Aluminum Electrical ConduitRigid Aluminum Electrical Conduit(one end needs to be threaded to engage flange)

1 600 Watt dimmer switch

1 wiring box to house dimmer switch

1 3-conductor electrical cord, 6, min. 16 gauge wire,with a molded 3 prong standard plug

A section of heavy gauge steel strap (10 gauge), wide Xapproximately 15 long (for socket carrier)

Plywood to bolt flange to

Section of 2X4 lumber at least as wide as the plywood

HighHighHighHigh----Temperature ElectricalTemperature ElectricalTemperature ElectricalTemperature Electrical WireWireWireWire NOT PLASTIC COATED!NOT PLASTIC COATED!NOT PLASTIC COATED!NOT PLASTIC COATED!Due to the high heat generated by the halogen bulb, theDue to the high heat generated by the halogen bulb, theDue to the high heat generated by the halogen bulb, theDue to the high heat generated by the halogen bulb, theinsulation of the electrical wiringinsulation of the electrical wiringinsulation of the electrical wiringinsulation of the electrical wiring MUSTMUSTMUSTMUST be rated forbe rated forbe rated forbe rated fortemperatures in excess of 400 degrees Celsius.temperatures in excess of 400 degrees Celsius.temperatures in excess of 400 degrees Celsius.temperatures in excess of 400 degrees Celsius.

UnUnUnUn----insulated crimp terminals for the Highinsulated crimp terminals for the Highinsulated crimp terminals for the Highinsulated crimp terminals for the High----Temperature wireTemperature wireTemperature wireTemperature wire(no plastic(no plastic(no plastic(no plastic used in the hot zone)used in the hot zone)used in the hot zone)used in the hot zone)

Whatever fasteners are necessary to hold everythingtogether

Scrap steel sheet metal for heat shielding

Twist-on electrical connectors suitable for 16-gauge wire


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WIRING DIAGRAMWIRING DIAGRAMWIRING DIAGRAMWIRING DIAGRAM

Hot Wire (Blk) Dimmer Hot Wire (Blk)

< To plug

Neut. Wire (Wht) Ground (Grn)

Toward front >

The wires shown in orange should be the high temperaturewire. Any wiring that will be inside the heat chamber (thealuminum conduit) MUST BE THE HIGH-TEMP WIRE.

The dimmer switches will typically have short pre-wiredpigtails on them. Connect the high-temperature wire and the3-conductor cable to these pigtails with twist-on wiringconnectors (inside the mounting box, away from the heatchamber).

The ground connection to the steel strap, and theconnections made to the halogen socket, should be made withthe un-insulated crimp-on lugs. Ring-type terminal lugs arepreferred over fork-type lugs.

LINE

LINE

LOAD

GND

Halo en Bulb

Socket

Steel Strap


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CONSTRUCTIONCONSTRUCTIONCONSTRUCTIONCONSTRUCTION

Make a hole toward the center of the plywood piece as bigas the hole in the center of the flange to pass the heatingassembly through. Center the flange on this hole, andfasten it to the plywood with wood screws. Polish and clean

the section of aluminum conduit, and thread it snugly intothe flange. The 2X4 block is fastened SECURELYSECURELYSECURELYSECURELY below theflange (on the back side) as a place to fasten or clamp thebending iron to a bench top.

Mount steel heat shield here to

protect wire from socket front.

Heat shield removed to show

Bracket construction. Do not

Operate without heat shield.

This is the basic layout of the heating element mounted tothe heavy gauge steel strap. The wire bolted to the strapat the left side of the picture is a safety ground wire.DO NOT OMIT THIS WIRE! Make sure it is fastened tightly toDO NOT OMIT THIS WIRE! Make sure it is fastened tightly toDO NOT OMIT THIS WIRE! Make sure it is fastened tightly toDO NOT OMIT THIS WIRE! Make sure it is fastened tightly to

the steel strap.the steel strap.the steel strap.the steel strap. If something goes wrong, this may be theonly thing that keeps you from being electrocuted.

Fabricate a steel heat shield 1-1/4 to 1-1/2 wide and aslong as the halogen bulb, and mount at the location shownon the above picture (under the bulb). This will helpshield the forward wire from the intense heat of thehalogen bulb. DO NOT OPERATE THEDO NOT OPERATE THEDO NOT OPERATE THEDO NOT OPERATE THE BENDER WITHOUT THIS HEATBENDER WITHOUT THIS HEATBENDER WITHOUT THIS HEATBENDER WITHOUT THIS HEATSHIELD!SHIELD!SHIELD!SHIELD!


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Mount the halogen socket about 1 back from the front ofthe steel strap. Fasten securely with machine screws andnuts.

Attach the high-temperature wire to the halogen socket(both ends) and the steel strap.

The entire assembly is inserted from the back of thebending iron (through the hole bored through the plywoodpanel) into the aluminum conduit. A small tab bent down atthe front of the strap engages a notch cut into the frontof the conduit. The strap is bent down at the back end fora tight fit in the conduit, and is fastened to the plywoodwith a small wood screw.

TAB DETAIL (FRONT OF CONDUIT)TAB DETAIL (FRONT OF CONDUIT)TAB DETAIL (FRONT OF CONDUIT)TAB DETAIL (FRONT OF CONDUIT)

Complete the wiring to the dimmer switch inside theelectrical mounting box. Use twist-on connectors to attachthe high-temperature wire and the plug cable to the dimmerswitch (see wiring diagram). The electrical mounting boxshould be grounded to the rest of the components.


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TESTINGTESTINGTESTINGTESTING

When the socket is wired and mounted to the steel strap,and the sheet steel heat shield is mounted in place, thehalogen bulb can be placed in the socket. Do not handle thebulb with your bare fingers oil from your skin will leave

a spot on the bulb that will cause localized heatinginternal to the bulb, and will prematurely shorten itslife. When the bulb is in place, mount the strap assemblyin the conduit, making sure the forward wire is runningunderneath the heat shield. With the wiring completed andall the components securely mounted, the unit can now betested. Turn down the dimmer switch to the OFF position,plug the cord into a 3-prong (grounded) outlet, and turn iton. Slowly increase the dimmer setting until you observethe bulb glowing inside the tube. Continue increasing thedimmer until the setting is at maximum. The aluminumconduit will rapidly heat up at the full setting, and willretain heat for some time, so use extreme caution around

the tube area. NEVER LEAVE THE BENDER UNATTENDED WHILE ITNEVER LEAVE THE BENDER UNATTENDED WHILE ITNEVER LEAVE THE BENDER UNATTENDED WHILE ITNEVER LEAVE THE BENDER UNATTENDED WHILE ITIS PLUGGED IN AND ACTIVE!IS PLUGGED IN AND ACTIVE!IS PLUGGED IN AND ACTIVE!IS PLUGGED IN AND ACTIVE!

As the tube heats up, there may be some initial smoke fromthe residue on the conduit or the socket, but this shoulddissipate fairly quickly. If you notice a great deal ofsmoke, visible flame, electric arcing, smell meltingplastic, or observe anything that seems wrong, unplug theunit immediately. Do not use it again until the problem canbe identified and properly remedied.

To keep the heat in the forward section of the tube, asmall sheet metal guard can be mounted over the hole in therear of the plywood. Take care that no sharp edges cut intoor rub on the wiring.

Once the bender has reached operating temperature (a waterdrop on the surface of the tube will sizzle and turn tosteam instantly), reduce the setting to maintain just theheat needed to bend the samples you are using. This willtake some experimentation to get the exact results desired.Make test bends on samples of the same thickness andspecies of wood before attempting bends on your intendedfinished parts.

A temperature probe, such as that found on a barbequegrill, or a non-contact infrared thermometer, can be usedto gauge when the bending iron is ready, or to adjust theheat for more repeatable results.

As different species of wood respond differently whenbending, it is best to consult with sources most familiarwith a given wood for information regarding how best toproceed.


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REALLY IMPORTANT NOTES ON SAFETYREALLY IMPORTANT NOTES ON SAFETYREALLY IMPORTANT NOTES ON SAFETYREALLY IMPORTANT NOTES ON SAFETY

As has been stated before, this device employs dangerouslevels of heat and electricity, and should be treated withextreme caution and respect. No tool is worth risking yourlife or health for, so if you are in any way uncomfortable

about the procedures shown in this document, do not attemptconstruction of this device.

The use of heavy leather welding-type gloves will furtherreduce the risk of accidental contact burns orelectrocution.

As a further safety precaution, it is STRONGLYSTRONGLYSTRONGLYSTRONGLY recommendedthat a ground-fault safety circuit be used to power thisdevice. This can take the form of a ground-fault receptaclemounted at the wall, or a ground-fault enabled extensioncord. This safety circuit will protect you fromelectrocution in the event of a short-circuit wiring fault

in the bending iron or any other electrical device, forthat matter.

Inspect the iron before use EVERY TIMEEVERY TIMEEVERY TIMEEVERY TIME for looseconnections.

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