Graphite Shafts and Bore-Through Heads

Frequently we at Harrison are asked questions regarding the installation of Harrison shafts into hoselless club heads like the Big Bertha. What follows are the most commonly asked questions and the answers that Harrison feels are the most accurate at the present time.

Why do I need to countersink the head and use a ferrule?
Because the inner edge of metal woods (and irons for that matter) are extremely sharp! Epoxy alone is not enough to hold the shaft still at impact. The shaft will vibrate slightly against the sharp edge with every single golf shot. Over time, that sharp edge will gradually cut through the graphite fibers resulting in delamination or breakage. The edge of the bore must be countersunk with a 20 degree countersink tool to create a chamber that can be filled with epoxy. This will cushion the shock of impact. Also relieving shock is the use of a 20 degree countersink ferrule. The ferrule will further strengthen this highly impacted area,. Remember, countersink the hosel and apply a 20 degree countersunk ferrule when installing all Harrison graphite shafts including iron shafts. Then you can rest assured that the shaft is covered with a lifetime warranty.

Can I use an O-ring instead of a ferrule?
No, if you want the shaft to be warranted for a lifetime. The O-ring moves around and is not as effective in supporting the shafts critical area as a ferrule. Your customer may not like the aesthetics of the ferrule, but the choice is up to your customer. He can have the ferrule and our lifetime warranty, or the O-ring and no warranty.

What effect will the bore through have on the shaft flex?
First, let's define the term bore through or through bore. This is a particular head design in which the shaft penetrates all the way through the head and sole plate. The shaft is actually visible at the bottom of the head in the form of a black dot. Because Harrison graphite shafts come in combination flexes, the most popular being the R/F - regular/firm and the F/S - firm/strong, it is imperative to tip the shafts correctly. In a standard metal head, to get a R/F shaft to go from regular to firm you simply tip the shaft one inch. The same is true for the F/S flex.

However, when installing a R/F flex shaft into a traditional bore through where the depth of insertion is a 21/2" to 3", the shaft will move up one entire flex without tipping. Therefore, to get a regular flex using a bore through head you must use an A/R flex shaft and not tip it, and to get a firm flex you must use an R/F flex. If the bore through length is less than 21/2", as is the case with the Big Bertha or hoselless heads, shaft flex will be affected but too a lesser degree. All of this information is based on a driver at 431/2"

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