How much variation in current flow from 14" full rod to a 1" rod nearly used-up?

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Hi,I was a farm machinery repair welder about 45 years ago using a Lincoln AC-225 buzz box.I am thinking about getting back into SMAW welding.  I got thinking.   If one were carefully thinking about fine adjustment of current setting, how much does the current flowvary from using a new 14" rod to using a 1" rod that is almost used-up?   Since the rod presents some electrical resistance, there is probably a difference in current flow through a new 14" rod vs a nearly used-up 1" rod.  Has anyone done testing or some calculations onhow the current flow increases as the electrode rod becomes shorter?I now have a Miller AC/DC 225/140 and an old 1960's Ideal Arc AC/DC 300/250 both which haveinfinite adjustment of the current setting.   Stated another way, if I were to set to a certain currently when I am starting out with a new 14" rod, how much do I want to decreasethe current adjustment (of the welder) as the rod shortens down to 1"?  Are we talking a current difference of 5 to 10 amps for a new 14" rod versus a nearly used-up 1" rod?Last edited by Orson_Yancey; 1 Day Ago at 05:16 PM.OrsonPortsmouth, NHLincoln AC/DC 225/125 flat top tombstone buzzbox Mfg. 2018Lincoln Idealarc 250 Code 5825-C, Mfg. 1966Dayton 240 volt spot welderOxyacetylene torch
Reply:I never gave it much thought. I guess with a clampon ammeter you satisfy your curiosity.Ol' Stonebreaker  "Experience is the name everyone gives to their mistakes"Hobart G-213 portableMiller 175 migMiller thunderbolt ac/dc stick Victor O/A setupMakita chop saw
Reply:All you've got to do is measure the resistance of a new rod and a stub.   Should be very low,  I doubt if it is significant for welding amperage variation.CG
Reply:A stick welder is a CC (Constant Current) machine, so it will do everything to keep the set current the same.Arc voltage varies with rod manipulation and arc length and could theoretically vary with rod length, but I doubt that the small resistance difference between a new rod and a stub will make much difference.Fronius Transpocket 180Kemppi minarc 150Esab powercut 400
Reply:Guys talk about the rod flowing smoother as the rod warms up. Maybe reduced resistance plays into that as well, but it's probably unnoticeable with the other factors at play. For a 1/8" rod, we are talking the difference in resistance between 1 and 14" of steel 1/8" in diameter... neither have a lot of resistance so it's going to be negligible.Last edited by whtbaron; 1 Day Ago at 06:48 PM.The harder you fall, the higher you bounce...250 amp Miller DialArc AC/DC StickF-225 amp Forney AC Stick230 amp Sears AC StickLincoln 180C MIGVictor Medalist 350 O/ACut 50 PlasmaLes
Reply:The answer is probably close to zero change in current. More than likely the voltage changes while the current stats pretty flat. SMAW welders are designed to deliver constant current.
Reply:I run a lot of 18", 7/32, 7024 rod and I agree with the others. There is no difference except the heat of the rod itself. A cold new rod will be exactly the same as a cold used rod of any length.Lincoln 330 MPXModified TombstoneLincoln LN-25X-TVTMagnum PRO 250LX GT Spool Gun¼ Ton of Torches OFC-A / OFG-ASMAW FCAW GMAW Air Carbon Arc Gouging#Freebird Welds
Reply:Never found time to worry.You find more variation in power company voltage from morning to afternoon. Most welders do notice voltage drop.Dave

Originally Posted by Orson_Yancey

Hi,I was a farm machinery repair welder about 45 years ago using a Lincoln AC-225 buzz box.I am thinking about getting back into SMAW welding.  I got thinking.   If one were carefully thinking about fine adjustment of current setting, how much does the current flowvary from using a new 14" rod to using a 1" rod that is almost used-up?   Since the rod presents some electrical resistance, there is probably a difference in current flow through a new 14" rod vs a nearly used-up 1" rod.  Has anyone done testing or some calculations onhow the current flow increases as the electrode rod becomes shorter?I now have a Miller AC/DC 225/140 and an old 1960's Ideal Arc AC/DC 300/250 both which haveinfinite adjustment of the current setting.   Stated another way, if I were to set to a certain currently when I am starting out with a new 14" rod, how much do I want to decreasethe current adjustment (of the welder) as the rod shortens down to 1"?  Are we talking a current difference of 5 to 10 amps for a new 14" rod versus a nearly used-up 1" rod?
Reply:A welder produces a series circuit. Power Ac Or DC flows from the welder through the work lead & clamp, through the table, workpiece, across the ionized gas produced by burning flux, & back through the electrode, stinger & its lead. The welder is designed to keep current steady. The rules of electrical theory are that a series circuit shares applied voltage. Resistance in each component of the circuit takes a bit of voltage. Ideally, the arc of ionized gas is the greatest resistor. Very tight arc, voltage decreases at the point of arc. Long arc, voltage increases. Heat is measured in watts. Watts are the product of Amperes X Volts. A long arc gives more heat, but that heat isn't where you want it. In comparison, I doubt length of rod will measurably change Amperage. And the machine will modulate to keep it steady.An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.
Reply:The only reason a rod seems to burn better after an inch or 2 is because the unburned rod is preheated. Same reason rods fresh out of an oven burn nicer on start up. Some large diameter Innershield wires calls for 4 inches or more wire stick out. This is to preheat the wire and gives vastly improved deposition rates.
Reply:Thanks for many good replies.  I am hoping to provide the needed electrical serviceso that I can get out there and burn some rods--more fun than just thinking about welding.OrsonPortsmouth, NHLincoln AC/DC 225/125 flat top tombstone buzzbox Mfg. 2018Lincoln Idealarc 250 Code 5825-C, Mfg. 1966Dayton 240 volt spot welderOxyacetylene torch
Reply:Hook up the Idealarc. It is a superior machine to the others.
Reply:prorbaly more change due to the way ur leads coil/unravel as u move around
Reply:

Originally Posted by Welder Dave

The only reason a rod seems to burn better after an inch or 2 is because the unburned rod is preheated. Same reason rods fresh out of an oven burn nicer on start up. Some large diameter Innershield wires calls for 4 inches or more wire stick out. This is to preheat the wire and gives vastly improved deposition rates.