Originally Posted by Harmonious
WU Tiger will be able to explain better but, in short, it has to do with the amount you cut off the tip of each raw shaft before you cut them to length and glue them together. If you cut more than standard, it makes the shaft stiffer than normal. Conversely, cutting less from the tip makes the shaft "softer".
As to adding weight to the butt end of your driver and 3W after shortening them, I don't get that. Cutting an inch will drop the swingweight about 6 points (D6 to D0, for example). He should have added weight to the head to compensate for the shorter length, if he wanted to maintain the same swingweight.
Harmonious explained the basic process well. For details, each shaft comes with a "trim code" that tells you how to trim it both for the club (Driver vs. 3W).
For graphite and iron shafts, manufacturers normally make one shaft for each flex, with trim codes for each flex version. A skilled clubsmith can trim a club to go between flexes: If an R-flex shaft says don't trim for a driver, you can stiffen the shaft by cutting, say, 2 inches off the tip so that the thicker part of the shaft is emphasized.
Some shafts, such as Project X flighted steel, come precut from the shaft maker and ready to install. Other shafts for irons generally come uncut, and the clubsmith does tip and butt trims according to trim codes for that shaft model.
For irons, there's lots of talk of hard-stepping or soft-stepping iron sets. Stepping affects he shaft by about one-third a flex. For a hardstep (stiffens flex), you put a 4-iron tipped shaft into a 3i, a 5-iron tipped into a 4i, etc. For a softstep (softens flex), you put a 2-iron tipped shaft into a 3i, 6-iron tipped into a 7i, etc.
For both hardstep and softstep, the clubsmith gets the club to standard length after the tip-shifting the shafts. (Softstepping is easiest, because you can trim the 2-iron tipped shaft to 3i length. For hardstepping, if you're using existing shafts pulled from the irons, you may have to lengthen each by a half inch.)
All this should hint at the benefits of a detailed clubfitting for someone with a reasonably stable - not necessarily excellent - swing.
Adding weight to the butt: this is called counterweighting. Back in the 1970s, some stronger players would put a fishing weight in the butt end of their shafts - especially drivers - to quiet their hands. This was mostly hit and miss back then.
Fastforward, Golfsmith did a study on counterweighting in 2004.
Here is a summary from another site. http://espn.golfsmith.com/display_page?page_num=cm_lp_mag0208_gca_insider_counterbalancing
I had a 4-gram plug in the driver shafter after I added a Harrison Shotmaker insert. I seemed to get a little better handdrop with the counterweighting. From what I heard at recent demo days, club makers are considering counterweighting for clubs with very lightweight graphite shafts (50 grams and under) to reestablish balance feel of the club.
Club designer Ralph Maltby avoids counterweighting because he says it increase clubweight and slows clubhead speed. If you shorten a shaft by 1/2", this drops swingweight -3. If you lengthen a shaft by 1/2", this increases swingweight +3.
Basically, if you don't know what you're doing, you can mess up a nice set of clubs by sawing on the shafts.