First I would scribe a line at 20mm and hacksaw offf the 1st unwanted 10., you can clean up the cut with a file if needed. I would then sit the job on a thin parallel in the milling vice such that the remaining 2mm or so can be machined off the sawn edge.

Guaranteed that if you only mill off one side it will bend due to the stresses induced by the milling.

Do as Tony says but instead of taking off the full two mm, rotate after one mm and reduce the other side by the remainder.

Lofty

Too long for my bandsaw and I'm too lazy to hacksaw that much by hand.

Easy way for me would be to put it in my milling vice and cut down 6mm with the base of a 4-flute end-mill . (Turning over to do the other side.)

Actually, to preserve the precious end of the cutter, I'd go the extra mile by removing the vice and clamping the work direct to the table with packing underneath so I could use the rarely used upper part of the flutes to cut the 6mm edge sideways.

I normally use a 10mm carbide end-mill flat out for bulk work like this – no lubrication, and hacking as much metal off as the machine will do without complaining. It gets HOT! If the finish demands it, I switch to HSS plus lubrication to do the final cuts. If HSS is used to remove a lot of metal, I flood cool.

Dave

To stop the issues of distortion I automatically normalise bms before machining. Easy to do, heat to red hold for a couple of minutes and cool slowly, I usually cover with a couple of fire blocks to slow the cooling. You can then saw the excess of either side and skim in the mill to size.

You could have bought 3/4 x 1/4(19.05 x 6.35) and not worn your cutters out so much.

Michael

My local stockholder would have done you a full 3m bar 1/4" x 3/4" or 6x20mm BMS for lots less than £20.

Neil

I think I would have cut the strip off by hacksaw. About two minutes' work at most. It's only a 100mm cut in 6mm plate. Then one finish cut in the mill and it's good to go. I have never seen flat bar bend significantly when machining off one side on the "long" side like this. Takes a bit of force to bend steel 18mm thick. If you were machining the "short" side down from say 6mm to 4mm you might be more likely to experience bending if only one side were machined.