There are many interesting discussions on hooks in this forum but I’ve had a question that has never been addressed. Regardless of a hook style, length or any other variable a hook is given a size number. What is the basis of this? Does it relate to gap (gape) in some mathematical way? If this is the criteria, why do some hook styles not compare to others in this dimension? How do you measure Gap on a Scud hook?
This may seem trivial but I’m just curious.
As far as I know, hook companies designate their own sizes. I read an article in “Fly Tyer” a few years back (still have the issue) that compared tiny dry hooks. Some companies had size 22’s that were actually smaller than others 28’s and so on.
This should make everything perfectly clear:
gOOD QUESTION RAY, I THOUGHT ABOUT IT AND THOUGHT ABOUT IT, TRIED RESEARCH .LOCAL SHOP “EXPERT” USES ONLY THE LATEST “NEW” STYLES. NO HELP THERE, SO I AFTER MUCH CONSIDERATION I GAVE UP THINKING ABOUT IT, AND GO WITH THE STYLES THAT HAVE NOT FAILED ME OVER THE YEARS.
Years ago I was getting confused about what the size of a hook actually meant as far as how big what part was.
One companies number six looked just like another companies number one ought. Size sixteen dry fly hooks from one company had gapes the same size as the mumber twelves from another hook maker.
None of the table or comparisons I found on line made any sense. They only compared style or shape of the hook and didn’t adress size.
So I decided to do it for myself.
I looked for what I would use as a standard hook. What I choose was the Mustad 3366 straight eyed sproat hook. I also decided that, for me, the size number related only to that distance from the hook point to the hook shank, or what is often called the hook gape distance.
I bought a package of each size I could get of this hook. At that time I could get them from size sixteen up to size three ought. Smaller or larger than that, I decided that it didn’t matter enough to bother with.
I taped one of each to piece of card stock.
I just compare the gape of any odd sized hook to the samples. That gives me the size. If the shank is longer than the standard, it’s along shank hook .I can figure out, if I want to, how much longer it is by measureing the shank against the larger hooks. If it is shorter than the standard, it’s a short shank hook. If the wire is heavier, lighter, etc., you get the picture.
I can now know what size a hook is to me. I emphasize the ‘to me’ part of this. Since no one out there has an industry wide standard, I found my own. You can do it your own way if you really care enough to bother with it.
You’d be amazed at how often the size as listed on the boxes differs from my standards.
Buddy
Hooks vary but so does nature. Length of nymphs and adults vary during a hatch as does coloration. A size 12 in one hook may not be the exact same length of a size 12 in another hook but both will likely catch fish for MOST hatches. Where size matter the most is when the hatch is tiny and a small variation in identical hook sizes can be a whole size difference from one brand to another.
Buddy was actually on the right path with the way he analyzed hook sizes. It might be worthwhile to note however that his base hook was a straight eye. Having said that, imagine a turned down eye and how it has the effect of making the gap smaller. If the eye is a good deal further from the hook point as would be the case with say a size 10 dry fly hook, the effect of the turned down eye would likely have no impact on fish hooking ability.
However, picture a size 24 dry fly hook with a turned down eye. The gap has now been considerably infinged upon by the turning down of the eye, This could cause lost fish. There are straight eyed hooks which can be used and these should be seriously considered in the smaller sizes especially.
The long and short of it is simply there really is little uniformity between manufacturers. On most occasisions for fishing flies, you are better off selecting what your experience dictates as a proper hook for a specific fly. Until you gain that experience try to follow patterns and experiment.
Tying flies for fishing is like cooking, the ingredients and recipes vary from one place to the next, for example Chile is many different things to many different people. So can flies for fishing be.
Now if you are going to tie for show, you have moved from cooking to baking where the substitution or changing the quantity of any ingredient can result in your cake never rising!
If you look around you will find the Elk Hair Caddis tied on dry fly and wet fly hooks, extra short and extra long. I doubt seriously that Ed Toth would care as long as you are happy and catching fish.
If you are going to tie for show, please don’t tie a flat cake!
Tight lines
George
Maybe some day the manufacturers will all sit down and decide to outdo world peace by standardizing hook sizes, thus making life easier on the next generation of fly tyers, while confusing the heck out of anyone who already thinks in terms of flies being measured by the hook size.
Consider what it would take to describe a hook, though. A designator of some sort for EACH measure of a hook.
Eye style (ring, blind, whatever)
Eye shape (up, down, flat, sideways…)
shank length (I vote for millimeters on this one!), assuming of course a straight shank…
shank shape (straight, scud, kinked, whatever)
gap (which would have to be defined for odd-shaped hooks like scuds)
curve style (sproat, limerick, etc)
Wire diameter (again, I vote for millimeters)
barbed (and what kind) or barbless…
hook steel type (stainless, carbon…)
hook color…
So, the TMC 900 BL hooks I prefer for itty bitty dry flies have a regular down-eye straight-shanked hook with a round bend, no barb, and are black in color. An 18 has a shank length of about 5mm, a gap of about 2.4mm, a wire diameter of about 0.3mm, black carbon steel…
R D 5.0 S 2.4 R 0.3 N C K
(Regular Down 5mm Straight 2.4mm gap Round bend 0.3mm wire No barb Carbon blacK)
Simple, right? 
But it is the only way I see to accurately describe a hook, other than all of the features I undoubtedly forgot in my list…