For this article, “What to look for when buying a used welding machine,” I am going to assume that you already know what kind of used machine that you want to buy. In the event that you don’t know or are not sure, please jump over to my featured article, “As a Beginner, What do I need to Start Welding?”
That article will walk you through the decision-making processes of deciding which type of machine is best suited to what you would like to accomplish.
Name-brand welding machines like Lincoln, Miller, and Hobart are typically very ruggedly built. If not abused they should provide years of great service.
However, like most, I am always cautious when buying used equipment. Especially, when buying used electrical equipment. And since welding machines are electrical equipment on steroids, one should take an extra dose of precaution when considering the purchase of a used one.
If you are a beginner, locate someone with experience if you can. Someone experienced in using the very type of welding machine you are looking for. This could keep you from making a mistake right off the bat. And you will probably pick up some pointers in the process.
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The external appearance of a used machine may or may not be a clue to its working condition. It may look brand new on the outside but may have a hidden issue internally. On the other hand, the exterior might be scratched, faded, dented, paint-splattered or otherwise appear to be worn out and yet be almost new with very few welding hours on the more important components.
One item that needs to be in good condition on the box is the faceplate. The faceplate will have the labels indicating amperage settings. It will also have all other instructions necessary to set the machine up properly for each job. If the lettering on the plate are not legible or missing completely, it is going to be very difficult to change settings with any accuracy.
However, you may be able to purchase a new faceplate, if damaged, depending on the age and model. Note: Be sure to snap a picture of a well-worn faceplate before it becomes impossible to read.
Power cord and welding leads
Next, check the power cord and welding leads for damage. Welders are constantly working with sharp, heavy pieces of hot metal that occasionally fall onto these vulnerable parts. If the outer insulation is damaged, crushed, missing, crumbling or hardened due to age, be prepared to replace them. Preferably, prior to using the machine for the first time.
Look closely at the welding handle for damage. A broken welding handle could expose you to electrical shock depending on the type and the damage. Replacing a stick welding handle is relatively cheap compared to MIG and TIG welding handles.
For more information relating to shock hazards while welding, please refer to my article, “Can I get shocked while Welding?”
Amperage and other control dials
Missing or broken control knobs and handles will make adjusting the settings very difficult if not impossible. While not always a deal killer it would be wise to check with the manufacturer in advance to see if new knobs or handles are still available for that particular model before purchasing.
Another thing, check to see if the dials will actually turn through the whole range they were designed to. The amperage setting control mechanism is typically not made to be adjusted while welding is in progress. Doing so can cause an arc in the dial mechanism itself causing severe damage. If you feel rough spots or find the amperage control hard to move at any point when turning it from it’s highest to lowest setting, you may want to pass on purchasing it.
Used welding machines with lots of hours on them may have cooling fans with worn bushings or weak motors. After determining the fan motor works, listen closely to determine if there are any unusual noises emanating from the fan. Worn bearings and bushings will not sound as quiet or be as smooth running as newer ones.
Pay close attention when the fan is winding up when first turned on and when winding down after powering it off. If it makes unusual noises, the cooling fan may not have much life left. In the event, the fan was to quit working in the middle of a long welding session, overheating the main components could easily damage the machine beyond repair.
Engine driven machines
A used engine-driven welding machine needs a bit more scrutiny applied during the shakedown. If it will start, was it difficult to get started? Blue, black or white smoke from the exhaust should be a red flag. Blue smoke indicates oil is getting into the combustion chamber.
Black smoke indicates the fuel mixture is too rich. White smoke only applies if the engine is water-cooled. White smoke emanating from the exhaust could signal a blown head gasket or a crack in the engine allowing water to enter a cylinder.
If the engine is difficult to start, the cause could be something as simple as well used spark plugs. Or, as complex as worn out piston rings. One thing to look for is, of course, fuel in the tank. Then, ensure the fuel lines are in good shape and not cracked or split. An opening in the fuel line will cause the pump to suck air and no fuel will get to the carburetor.
A worn cylinder or rings may not provide enough compression to allow the engine to start and run well. If you think the engine may be worn out, ask to do a cylinder compression check. You will need to know the correct engine specifications to check against in order to determine if the compression is within its correct range. If the compression is good on all cylinders, a slow starting or rough running engine could just need a tune-up, filter change or carburetor kit.
The gauges should be in good working order. You will be unable to determine if the engine is in good condition if the gauges are not working or, are giving faulty feedback.
Is the battery strong? A weak battery will soon need to be replaced.
If the engine knocks, that typically indicates an issue that is rarely cheap or easy to repair. Keep looking until you find a used welding machine worth the money to be on the safe side.
All potential costs to get the engine back in good running condition should be weighed against the asking price.
Will it weld with no issues?
Any seller who is not agreeable to allowing you to test the machine may be hiding something. On the other hand, there could be circumstances where you will not be able to check the machine out closely before buying.
Some auctions or estate sales may not be set up properly to allow the machine to be tested on site. Under these circumstances do the best you can and be prepared to lose money if you end up buying a dud. You could end up scoring a very reliable machine for a decent price but never spend more than you are prepared to lose.
If you are allowed to weld with the machine, and I hope that you are, look for consistency in the arc voltage. Weld for a few minutes on a range of settings. Again, look for a smooth, consistent arc over time. Any strange voltage fluctuations, noises or smells should be a reason for caution.
It never hurts to ask for a trial period if the machine cannot be tested on site. A trial period of 48 hours should not be asking too much. And of course, the answer will always be no if you don’t ask.