#10 screw and 3/16 screw

[mardtrp]

Oh the joys of playing with that outdated MONGREL system , it's about time you lot converted to the easiest system of them all, metric.


Mark

[Machinist-Guide]

Drill Chart

Here is a link to a tap drill chart for number screws if you need one

Number Screw Tap Drill Chart

[Rich Carlstedt]

The switch from Inch to Number measuring for "small" threads produced some
wierdcases. These are generally threads less than 1/4"
In Number Screw sizes, You start with .060 as a base and it is a 0-80 thread, or 0-72 etc.
( Please note that .0625 is 1/16 , so " )" is close to that fraction benchmark)
Each sequential thread size grows by .013" and gains one digit.
A 1-72 for example is .073" and a 2-56 is .086 in the "Major Diameter" measurement.
A 10-32 is .060 PLUS .130 ( 10 x .013) or .190
Your old 3/16 thread is .1875"
The only "exact" one is 1/8-40 (ie.) as it meets a 5-40 (.060+.065) at .125 dead on.

Real confusion is with the #14 threads (.060 + .182) as its .242
So if you have a 1/4 -20 bolt, it will not fit a 14-20 hole !

Old machines and hardware still use the old standard of 100 ago

Its a lot easier, to refer to numbers than fractions.
Can you imagine doing a 5/64-72 or a similar ?
It was an attemp to make the range smaller than 1/64's
Of course it doesn't get a simpler than Metric..but I won't go there

Rich

[Don Young]

I don't know the exact specifications, but for common hardware they are basically the same. I think that 3/16-24 is pretty much obsolete, replaced by 10-24. The preference seems to be to use inch dimensions for 1/4" and above with machine screw numbers for smaller sizes.

[rotate]

I'm feeling like an idiot. I have box of set screws marked 3/16-24. I was looking at my tap & die set and noticed that I don't have a 3/16-24 tap, but #10-24 looked almost identical so I used that. It worked although the set screw felt a little loose.

So, what's the deal with #10-24 and 3/16-24? I feel like such a space cadet.