looking to buy a vac for sucking fine dust when polishing.
what is the best or would work in kpa suction.
so far found 18 kpa and 15 kpa.
watts doesnt mean a thing from what I can gather. had a 1500 watt hoover and it was useless(in the house)
There is a big difference between vacuum cleaners and proper dust extractors. Vacuums use the air flow to cool the motor and can overheat and shut down if the flow is restricted. Dust extractors can be used 8h a day, 6 days a week without complaint. Have a look at the filtration class as well - class M is the current minimum. A class M machine will have all the correct filters and also an indicator when the filters need cleaning.
For a cheap, but adequate one, look at the V-tuf. It is built to be the minimum class M possible, but if you are using it yourself and are not heavy-handed with it, it might do what you need.
As you say, wattage is not a reliable indicator as that is only input power. The back of a 3kW fan heater sucks cold air in but you would not use one of them...
I'll be just using it now and gain. today for example polishing for an hour.
the most time I spend polishing is about 2 hrs but thats it.
probably about 30/40 hrs a year if that.
I dont do a lot these days.
I have a V-Tuff mini in the house, it has a very flexible strong hose that doesn't kink, perfect for attaching to hand held power tool. Most other cheap vacs are let down by their hoses.