MIG Welding

Hosts ToolCraft & Dave Littleton

May 20^th 2006

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Presenter David Littleton brought his welding equipment and set up demonstrations and practice coupons for us to try.

The focus of the demo was the Harbor Freight Dual MIG 131 welder model number 6098. This is a 110V machine with 80 amp max capability at 20% duty cycle. This machine is rated capable of welding 3/16" steel at the max setting of 85 amps. David has used this machine with great success as a home hobby machine. This machine is frequently on sale at Harbor Freight for approx $190. 

To complete the setup as demonstrated, David bought a gas regulator ($33), gas bottle, welding cart, and replaced the ground clamp with a larger capacity one. David recommends the welding cart that includes a place to mount and secure the gas bottle.  A gas flow regulator with a flow meter is a better solution to the gas regulation need. These regulators cost about $70. They meter the flow more accurately.

David pointed out there are other brands of MIG welders on the market that have well known brand names and are excellent quality machines. Their higher cost are a significant consideration for the home hobby welder.

The demonstration of the gas shielded welding used a mixture of 75% Argon and 25% CO2.  For welding stainless David recommends 100% Argon or a Tri-Mix gas. David showed several sizes of gas bottles. The smaller ones seem handy at first, but they do not hold enough gas. The refill charge on the smaller tanks and the trouble of transport back & fourth dictate getting a minimum 60 cu ft tank.

Auxiliary equipment needed 

• Harbor Freight has a good MIG welding pliers for $10. This unit includes the special grip jaws for removing and tightening the welding tip.
• Extra welding tips. They come in 3 sizes. .023, .030, and ,035. The wire size used determines the tip size to be used.  The Harbor Freight welder uses standard tips. Tips for Lincoln and other welders will fit.
• Spools of wire. Wire comes in 3 sizes. .023 wire is used for thin material welding. .030 is the standard wire. .035 wire is for thick material. Wire is available in 3 spool sizes. The Harbor Freight unit uses the 4" spool size as a standard. It also includes an adapter for the 8" (10 pound) spool. The 12" spool as used in bigger machines holds 33 pounds of wire.
• Good stainless steel brushes for cleaning the material and removing weld splatter. A stainless steel brush dedicated for cleaning aluminum material prior to welding is a must. It is used to polish the material to a high shine just prior to welding
• Angle grinders). David uses the angle grinder for sanding, cutting, and grinding the material and welds. He recommends having more than 1 grinder to minimize change over time. The cheap Harbor Freight units have served him well. With the extended warranty feature, they are a great value for this application 
• Auto darkening welding helmet. Again Harbor Freight has a good auto darken helmet that often goes on sale for about $50. This is a great value for the home hobby welder. If you experience headache while doing welding, the response time to the arc strike may be the trouble.
• The arc light from welding can damage the exposed skin.  Good gloves and skin covering is a must for safety.
• Fire prevention. Remove flammable material from the area where welding and grinding is done. The home hobby welder often works in the driveway or the yard. The sparks from the grinder can start fires as well as the arc and flash from welding. Keep buckets of water and/or fire suppression equipment handy in case of fire.
• Full face shield for grinding. The sparks from grinding can damage car paint, melt into glass, etc. Protect your face and eyes when grinding
• Cooking spray. The cooking spray suitable for applying to a hot pan is a must. Spray this material on the welding tip and inside the gas shield. This helps avoid the buildup of weld splatter in and around the welding tip. David recommends using this spray once per hour, or when ever fixing a splatter issue with the tip.

Welder set up and prep

The gas flow meter should be set to deliver 12 to 15 cubic feet per hour (CFH). You may need higher flow if outside in breezy conditions or an atmosphere where the gas shield may be disturbed by air currents around the work site.

When loading the wire spool in the welder, be careful to hold the wire on the spool to keep it from uncoiling. Until the end of the wire is retained in the wire feed wheels, the wire on the spool tends to uncoil from spring action.

The wire feed mechanism in the machine has grooves suited for the different sizes of wire. Select the appropriate sized groove for the wire to be used.

The tension adjustment on the wire feed mechanism should be adjusted per the equipment directions.

The wire should be set ½" past the gas shield to start welding.  When welding, adjust the wire feed rate to keep this wire spacing. The welder wire feed rate is originally set to pre-set speeds for the welding amperage selected. A fine adjust feature is included to tweak the feed rate as needed for the particular welding conditions.

• Safety Note: remember when you are holding down the feed button to feed the wire out the tip, the tip is live and ready to strike an arc. Be careful how you handle the torch to avoid shock or arcing to surfaces.

David demonstrated grinding a bevel on the edges of 5/16" thick material to make a butt weld with the machine set at max amps. This allows making welds even at greater thickness material than the machine rating.

David encourages a welding speed on steel of 1" travel in 5 seconds. He normally does not use the circular puddling motion unless welding extra heavy material.

MIG welding is a "coldstart" weld. The arc strike must raise the material to melting temperature. Preheating the material can make the welding start easier. If welding cast iron, you must do preheat.

David also demonstrated flux core wire welding without cover gas. The flux core generates the cover gas during the weld. This form of weld generates more splatter similar to conventional arc welding.  The splatter is easier to brush away after the weld.

When changing from solid wire to flux wire welding with the Harbor Freight welder, the polarity must be reversed. A chart inside the machine by the wire spool holder is easy to follow to make this change.

David also demonstrated welding aluminum with his Miller 210 MIG welder. Again he stressed cleanliness of the material at the start of the welding process.

Several club members tried the flux core welding. We found the process sounds simple, and looks easy. We soon learned welding requires practice to gain proficiency.

Updated 5/21/2006