If it was me, I'd install the screws with epoxy.
To remove the extra length of bolt above the deck, a cold chisel and
hammer, or sawzall.
To finish, a belt sander, but not dwelling in one place, keep moving.
Or if all you have is a body grinder, get a wet or dry sanding disk,.
Since you don't have much patience, that can be run wet.
DJ
On Dec 18, 11:07 pm, wrote:
If I've got this right, you drill and tap a hole, and then you plug the hole
so you are back where you started. Why?
Well, indeed, without the context this sounds pretty strange 
Iīll
explain it. The metal plate is actually the deck of my boat, which was
covered with teak wood. All these strips of teak were fastened to the
deck with screws. After removing the teak (because it become really
rusty underneath) I ended up with 800 holes, 5 mm. Which have to be
closed. At first I wanted to weld them, no worries about corrosion or
waterproofness. But on the inside there is sprayed-on foam which makes
the welding unsafe. To remove the foam all the ceilings have to come
out of the boat and to do that a lot of cupboards need to come out as
well. Unfortunately the boatbuilder used nails on a lot of places, so
it is really hard to remove interior parts without damage. Filling the
holes with some epoxy based filler would have been easy, but after
that it is impossible to sand blast, which is really necessary looking
at the condition of the deck.
So, therefore I figured out this method with drilling, tapping and
glueing bolts.
Since you don't put any torque on the bolt when you screw it in, why not saw
most of the way through it before you
screw it in? After the epoxy sets, break it off or finish sawing, and then
grind off smooth.
I thought about something like this too. Only I tried to do it with
the angle grinder. Problem was that this made the bolt so hot that the
zinc plating started looking strange and I had doubts whether the
epoxy would still adhere to it.
What you suggest, using a saw, would not be hot. But I donīt know if
it is possible to do this quickly for all the 800 bolts. I also live
on this boat. Well actually we are sailing around with it and have a
working break now. But I donīt have many nice tools. Handsawing this
quantity of bolts seems not very attractive to me. Maybe mounting the
jigsaw upside down? How would you do it?