Replacing brushes.
Motor on mine was an ACC.
The 4 small hex head nuts holding brushes to motor casting were quite bizarrely 4BA..
yes 4BA not metric at all.
Tried metric and nothing would fit..most odd..
so took mould with plasticine and measured..4BA
If nothing fits try a 4BA long thin box spanner and out they’ll come..
Never come across any modern appliance using such headed bolts..
presume done on purpose ??