Rohr Mig 250 FI

[RohrMig]

I have recently acquired the above Mig welder. I purchased a small reel of flux core wire to start with to make sure the welder worked. It does not seem as though you can reverse the polarity on this particular welder but it still made a reasonable job with the flux core once dialed in. So my questions are as follows.

Does it damage the machine long term if using flux core with negative earth?

What is a good gas set-up for a hobby-ist welder (the very small bottles 390g etc apparently do not last long at all and the regulators for them look cheap too).

For a bit of background: this will be welding farm machinery, I already have an arc welder, this came up and I took it as I have some thinner metal work which needs welding and the Arc will just stick or blow holes.

 

[eddie49]

Hello and welcome to the Forum.

The "FI" version of the Rohr MIG, as opposed to the "MI" model, does not offer polarity reversal ( and there is no Arc option either ).
However, using fluxcore wire without swapping to Torch negative and "Earth" positive will not hurt the welder at all - it just results in messy welds with low penetration.

It might be possible to modify the welder so polarity can be swapped at will. This would involve fitting a fly-lead for the torch and an additional positive Dinse socket on the front panel.

The small disposable gas bottles are not cost-effective. A proper cylinder and regulator is the only economic solution. Check the Shielding Gas and Regulators section here for information about the rent-free suppliers such as SGS, Adams Gas and Hobbyweld, and then look for what is available in your local area.

 

[zzr1200]

I have recently acquired the above Mig welder. I purchased a small reel of flux core wire to start with to make sure the welder worked. It does not seem as though you can reverse the polarity on this particular welder but it still made a reasonable job with the flux core once dialed in. So my questions are as follows.

Does it damage the machine long term if using flux core with negative earth?

What is a good gas set-up for a hobby-ist welder (the very small bottles 390g etc apparently do not last long at all and the regulators for them look cheap too).

For a bit of background: this will be welding farm machinery, I already have an arc welder, this came up and I took it as I have some thinner metal work which needs welding and the Arc will just stick or blow holes.

Whereabout in Derbyshire do you live?

It can be converted to run both fairly easily for not a lot.

 

[RohrMig]

I'm south of Chesterfield, Clay Cross.

I noticed that SDL Minorfern in Clay Cross do Hobbyweld gas bottles, never knew that!