20-->25 mil....??????

[Roly]

WTF is mil........ millionths of an inch or what????
Or. is it thousandths of an inch?
I'm picking it is thou's as then it would figger out.
Why call it mils then?
Maybe I'm just dense.

[duluthboats]

I may be wrong but I always understood that in the US 1 mil = .001 inch. (Edited to remove even more confusion.)

For some reason we have a million different standards out there and it gets to be a guessing game as to what is what. Wake up people it’s a small world and we have to communicate.
Gary

[Willallison]

...and without wanting to drag up the eternal metric vs imperial debate..... those of us living in the modern world would probably consider mil to be short for millimetre... (I know it's not btw).....

[tom28571]

Well, as Will said, in metric a mil is .001 part of a meter. Spoken as mil but written as mm.

In most other systems we use around here, a mil is .001 part of an inch or .0254 millimeter.

To an artillery battery a mil is 1/6400 part of a revolution.

Are there any more mils floating around?

[erik818]

In my work "mil" is an angular measurement used by the millitary e.g. in ballistic tables and in reticules. Within NATO there are 6400 mils to the full circle. Russia and other former Warsaw Pact countries use 6000 mils to the full circle. Sweden uses 6300 mils to the full circle. It's not called mils in the native languages, but thats how it's usually translated in English.

Engineers in all countries I've been doing buisiness with prefer mrad (milliradians) when exchanging information. There are 2*pi*1000 (appr. 6283) mrad to the full circle.

Erik

[duluthboats]

It seems I have again added to the confusion. Tom is right in the US 1 mil = .001 inch. It is a value that I seldom come across unless I’m looking at plastic sheeting. 1mm = .03937 inch is much more common in my day to day work.

Gary

[Willallison]

...then of course there's 'mil spec' - which has nothing to do with measurement at all!
Yep - sure is a global village these days....

[Roly]

Thankyou all. So it is 0.5 (roughly) mm. That is 20---> 25 mil;Ideal thickness for gelcoat.BTW I think (know) we made it thicker judging by the amount we used!
:-(

[fiberglass jack]

next time u do gelcoat get urself a mill gauge this will remove the guess work, its like a card with a set of mesurments on one side place on the gel and then remove the gel will show on the card what the mills are