# Drill size metric converter

Discussion in 'Getting Started' started by Topo, Jun 18, 2004.

1. ### TopoMember

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Used to metric measures, I always struggle when find references to inches and so, having to resource to the calculator.

But if we are speaking about #s of screws, drills, and so, I'm completely lost!
What is a tap 56-2? How many millimeters are a drill #50??? :curse:

It was a pity, because in the net there is a wealth of information written by fellow US & english modelers that work with imperial measures. :cry:

Enter the internet wonders: The drill size table & converter!!

http://www.csgnetwork.com/drillsizeconvert.html

My «calculator days» are gone now, and I wanted to put this link here. Maybe another «metric guy» find it of use! :thumb:

P.S.
Oh, I forgot to mention: in this link there is a BUNCH of other calculators, converters & tables!
2. ### 60103Pooh Bah

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Topo:
The National Coarse/National Fine screw sizes have 2 parts. First is the size of the screw -- the diameter of the rod. The second is the number of threads per inch.
And a 2-56 screw is a coarse thread!
3. ### Russ BellinisActive Member

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What is really confusing is that a 2-56 is not metric. The U.S. uses two different drill size standards. There are fractional sizes, and then there are number sizes. I think the number sizes are a result of the SAE. Automotive engineers needed more sizes than fractional sizes offered. How the sizes were established I don't have a clue.
4. ### RailRonActive Member

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Javier, thank you very much for this link. This is an outstanding collection of tables and calculators! :thumb:

Now if I only had an internet connection in my workshop...

Ron
5. ### 60103Pooh Bah

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I just had a look at the table. The wire sizes there are not related to the size of screws. In the screws, the numbers go down as the screw gets smaller; in wire sizes the numbers go up as the wire gets smaller.
6. ### TopoMember

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David...

Humm, I see... So 2-56 stands for 56 threads per inch, but what unit is the "2"? millimeters? inch fractions?

(BTW, in my first post, I wrote "56-2". Sure that this is a really weird screw!!
What a "typo" I made!! )

Rats! So I'm still without a good table relating the screw # sizes to their metric measures...
When I find his table I noticed that the header says "Wire No./letter", instead of "Screw No." or so, but I supposed -mistakenly- that they were the same, because the table is about drills.

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