Professor Hammer’s Metalworking Tips



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on May 12, 2016



Professor Hammer’s Metalworking Tips

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While most TIG welders have a high-frequency circuit to start the arc, some newer Miller welders have a Lift Arc feature that allows the arc to be safely started without the use of a high-frequency circuit. Read below to see where and why this might be desirable.


Q. What do you think about using an air hammer to planish (form) aluminum sheetmetal over a solid wood or concrete form to make large, elaborate sheetmetal parts?
Roland Djerf

Via the Internet

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A. You certainly can move aluminum (or steel) by using a handheld air-powered planishing hammer. Unfortunately, this only works well if you are bending or stretching the metal. If you put a flat sheet of metal over a convex form and try to hammer the metal down against the form, it won’t be long until you are trying to SHRINK the metal with each hammer blow, and the process stops working well at that point.

You CAN, however, work along the edges of a panel (as shown in the photo), or inside a concave form, and this works quite well.

Q. Due to the fact that I have a pacemaker (Oct. 2014), I can no longer TIG weld (because of the high-frequency emissions). I’m restoring a 1947 Studebaker pickup, and I prefer to butt joint weld patches and repairs.

How large a gap should I leave on the sides of a 5-inch square patch piece on a flat 18-gallon repair? I’ll be using 0.023 wire on a Miller 252 MIG welder. After welding my patch panels, is it wise to grind both the inside and outside surface smooth?

I’ve been welding for over 40 years but my work has always been industrial machine repair and fabricating, so this thin stuff will be a challenge. I sure miss the TIG welder.

Thank you, and I appreciate any help.
Joe Campoli

Mishawaka, IN

Via the Internet

A. Many people who MIG weld sheetmetal like to leave a gap about one material thickness between panels. I’ve tried it both ways, but my preference is for a tight fit.

It’s generally best to sand or grind the outside of the weld bead until it’s flush with the surface of the sheetmetal, but most of the people I’ve watched don’t bother to smooth the inside of the panel, unless there are unusually large “goobers” on the inside of the weld.

I fully understand that your doctor doesn’t want to risk compromising the function of your pacemaker by having you subject it to high-frequency circuits, but there might be a workaround that would allow you to continue TIG welding. When welding in the DC Electrode Negative mode (straight polarity), as you would be for welding steel, the high-frequency circuit only operates while the arc is initiated. The high frequency will jump the gap between the electrode and the work piece, allowing the welding arc to start without touching the tungsten electrode to the base metal, which can contaminate the tungsten.

Some of the newer Miller TIG welders have a Lift Arc feature, which doesn’t use high frequency at all. It allows you to start the arc by touching the electrode briefly to the base metal, but the flow of current is kept very low at first contact so the tungsten doesn’t get contaminated. Once the arc is initiated, the current ramps up to normal welding levels. This feature was developed to allow the machines to operate near sensitive electronic circuits.

You should definitely check with your physician first, but it’s very conceivable that this technology could allow you to continue to TIG weld, and I believe that TIG welding has many advantages over MIG welding.


You can email your questions to Professor Hammer at covell@cruzio.com, or mail to: Covell Creative Metalworking, 106 Airport Blvd. Ste. 105, Freedom, CA 95019; you’ll receive a personal reply! Ron Covell has made many DVDs on metalworking, and he offers an ongoing series of workshops across the nation. Check them out online at covell.biz, or call for a current schedule of workshops and a free catalog of DVDs. Phone (800) 747-4631, or (831) 768-0705. You’ll also enjoy Ron’s YouTube channel, youtube.com/user/covellron.




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