Burned my shop down . . . . . . . . . Almost!

[Steve Suesens]

I have a Lincoln Electric Weldpak 175HD (220v) Mig welder. It only comes out a few times a year - I am no welder but can usually make two pieces of metal stick together. Yesterday I fed a new spool of Fluxcore .030 on and began welding - the wire broke at the spool. I opened the side panel - re-fed the wire successfully all the way to the gun tip. I then fed more wire and watched as the wire between the spool and feed roller began to glow red hot then snap. I believe I have a short somewhere - but nothing is visibly touching. I would appreciate some advice on what to check.... Thanks
 

[MarkB_MI]

Hmm. Let me guess, the spool is steel, right? And the old spool was plastic?

My Lincoln SP-170 has a plastic spindle and the spool is secured with a plastic thumbscrew. The thumbscrew is easily damaged and replacements aren't easy to find. I'll bet if you replace the plastic thumbscrew with a metal one, then install a metal spool, the electrode will short to ground through the screw.
 

[Steve Suesens]

Update - The end of the spool was protruding out the side of the spool - grounding to the cover. Terrible design on the spool - but it is a plastic spool. I removed the offending wire end and added a rubber washer between spool and case. Problem solved. Thanks for your comments.