Welding Tips and Tricks

Q1: MB15 and MB25 tips - both fit the MB15 torch. Is there any disadvantage to using MB25 tips on an MB15 torch?

Q2: Flux core 0.8mm. After the wire has been fed thru the knurled roller I notice a scoring on the wire. When I try to feed thru a 0.8mm tip I feel some resistance. Will I see any adverse reaction if I changed the tip from 0.8mm to a 1.0mm tip? (I'll need to acquire 1.0mm tip to try).
Q2a. The scoring on the flux cored wire is from the knurled roller. Should I be concerned about the torch liner gathering fragments from these knurled scores? Liner is of the steel spring type.

Thanks for any suggestions.

A2: if you feel abnormal resistance, you could try a 0.9mm tip instead of going to 1.0mm directly. You're bound to feel some resistance since the knurled rollers do impart their signature onto the wire itself, but the question is: is the resistance abnormal compared to what you have experienced in the past, or is this an actual problem with effect rooted in causality?

A2a: Eventually after running a lot of flux cored wire with knurled rollers, yes the liner will develop particulate matter. You can try to "clean it" with high pressure compressed air and see if you can observe a thin cloud of dust out the other end of the liner. If so, mission accomplished. If not, and you are experiencing feeding problems, then simply buy a new liner.