[sdiy] electrolytic mechanical question

[Czech Martin]

I still have a box of 16 37000uF / 75V power supply ´lytics.
Got them for bargain at a surplus, arround 1989.
They are still in good condition, no leakage can be observed.

Now, they seem to have holes for M5 screws. Sprague, Siemens.
But somehow it is difficult to drive the screws in.

-could it be non-metric?
-could the holes be conical (that´s what I think)
-what else?

My guess is that I have to cut again the thread with a M5 tool.
OTOH this can turn out messy, it is Al after all.

Any sugestions would be highly appreciated.

m.c.