I thought I'd make a post clarifying how the Japanese manufacturers use Face Progression instead of Offset.

There have been one too many times where people have been confused by FP numbers using them as offset and saying that Japanese irons like the r7 Forged have "reverse offset (more offset in shorter than longer irons)" or other JDM irons have humongous offset. This is NOT the case.

To make things simple FP is a different measurement that can be used to calculate offset. The higher the FP number the less offset there is.

I've used the Epon AF-701 to illustrate.

Face progression measures how far forward (or behind as there can be negative FP) the leading edge (red line) is from the centerline axis of the shaft (blue line).

(IMG:http://www.inpakuto.com/scans/fp2.jpg)

Offset on the other hand uses the leading edge (red line) in relation to the most forward part of the hosel (blue line). When we think offset, it's usually the forward part of the hosel in FRONT of the leading edge.

(IMG:http://www.inpakuto.com/scans/offset2.jpg)

Another part of the confusion is that offset is measured typically in inches while face progression is almost always in millimeters. Yes it can be hard to compute in two different dimensions. (^_^)

Even though it doesn't seem like it, in fact the larger the FP number, the smaller the offset.

The key number to know is what the hosel diameter is (typical irons are around 13.6mm or 0.535" but that number mostly varies which adds to the confusion).

Using Face Progression to calculate, here are the offset numbers for the AF-701.

Offset is calculated by taking half the hosel diameter, the AF-701 has a 13.5mm hosel (13.5mm / 2 = 6.75) minus the FP and divided by 25.4 to convert mm to inches.

4 Iron Example: (6.75-1.55)=5.2, 5.2/25.4= 0.205"

(IMG:http://www.inpakuto.com/scans/701fp.png)

So hopefully this clears things up a bit... when you're looking at those Epon AF-301's and the FP numbers are getting larger, it does not mean the offset is more in the shorter irons!

One thing learning this calculation did show me though was that the AF-501 shorter irons have LESS offset than the AF-301 short irons!

Hope that all made sense and helps a bit the next time you look at FP numbers.

sticky...

T, you should post it on the 'other' forum. (IMG:style_emoticons/TSG_Smileys/tsg_smilie_laugh.gif)

One of the most important threads around T!

Thank You.

I think we are all tired about people constantly arguing this subject. A very patient work.

Great post T, I have always preferred using fp as opposed to offset; its such an easier concept to understand, the higher the number in mm the less offset!

Good post T. Thanks for the time and effort. The explanations and numbers are spot on. Although I think the pictures (especially the first one) might be a little misleading. In the first picture, the red line (leading edge) is behind the blue line (center of the hosel) which would indicate a negative face progression (HUGE offset) that we know is not the case for the AF-701. It only looks that way because of the camera angle. I believe both face progression and offset are measured with the hosel parallel to the leading edge when looking down at address. For most player/mid-cap irons, the leading edge will be in FRONT of the center of the hosel. So you can clearly see why more face progression equals less offset and vice versa.

Bat

This post has been edited by Bat: Jun 8 2008, 09:11 AM

Good point Bat i need to find better pictures... Perhaps I will take my own. (^_^) I'll remove those for now and go take some of my AF 701 from the proper angle.

T

Okay retook the pics at the right angle... tough to line it up by eye... the hosel parallel to the leading edge especially when we're talking measurements in mm!! (^_^)

Wow, that was fast. Great job T.

Bat

I will get flamed for this here but I have to express my thoughts.

Face Progression and offset are ways to measure hosel position in relation to leading edge. The "reverse offset" I always refer to is a design concept. It can be very small like in the 04 RAC CBs, or very noticeable like in late 80's early 90's Japanese designs.

I think the confusion stems from the fact that face progression has often times and mistakenly been referred to as a "reverse way to measure offset".

[b]Face progression and reverse offset (as design) are two totally different things.[/b] It just so happens that FP reflects the numbers/measurement in "reverse" lower to higher. Coupled with this design concept there has been a tendency to confuse one with the other.

What I refer to can easily determined by even the naked eye. Take a look at Japanese Miz irons from the early 90s. All the time the complaint is the "PW is a shovel". Even one of the MPs (I can't remember if it was the 14 or the 29 has the same problem).

Among the newer blades the Pro100 is a great example. Take a look at the pw and compare it to the 5iron. Just by looking you can tell the PW has more offset than the 5iron. No measurements needed.

TB1000 vs TC1000. The TB1000s pw hardly has it compared to the rest of the set, the TC1000 set has it noticeable but only after you put it beside the TB1000 set.

In fact what Gocchin's post has shown me is that FP and offset are in no way related and FP is not even a "reverse way of measuring offset" because the baselines/axes used are
different.

Maybe unpopular but that is my opinion and my experience. I have looked at my Pro100s over and over and still can't imagine how they can put such a wedge in an almost perfect set.

No Problem XXIO, your opinion is definitely much appreciated (^_^). This is a discussion board after all so everyone's comments and opinions are very welcome!

Perhaps I have just not come across any irons lately with noticeable reverse offset and if brands do possess them like the Fourteen you mentioned, they don't advertise their FP numbers.

I wasn't saying that reverse offset does not exist, I was just saying may people unfortunately just look at FP numbers and mistake them for reverse offset or humongous offset which as we all agree is not the case.

I think I should take some pics of iron face progression and post them up here.... first I need to find a set with real obvious reverse offset. (^_^)