Summerlin interestingly commented on my last post that shinai tsuka have changed over time and that this may have an effect on the way that we learn tenouchi. This could certainly be a contributing factor. I am a firm believer that kendo is subject to fashion and change. In the eighties and early 90s we saw bogu with brightly coloured kazari; the rule now is the plainer the better. Equally, over time there have been various changes to tsuka and tsukagawa. I am not thinking of the recent snazzy additions of coloured trim or dragonflies on the nigiri, but of physical changes to size and shape.
Whilst the overall dimensions of shinai have not changed since the mid 1800’s, there seems to have been considerably variation on the length of tsukagawa and the percentage of the shinai that it covers. IKF regulations are stringent about the length and weight of shinai. There are also strict specifications for the diameter and length of sakigawa, but to the best of my knowledge no rules apply for the length and diameter of the tsuka. The only limiting factor being that the tsuba must rest on the bottom edge and not leave a gap between the tsuba and the bottom of the tsukagawa.
Looking at videos of pre-war kendo, tsuka appeared to be longer than those used now. I have also seen shinai from the 1970s where tsukagawa had obviously more length than their modern counterparts. In the 90s we went into a period when shorter was better. Most of my kendo friends in Japan were specifying 38 tsukagawa on 39 shinai. More recently we have seen a trend for shinai to be made with much bigger diameter handles, many of these coming from Chinese manufacturers for export to the west.
Whilst I see the logic in buying shinai that fit your grip in much the same way as would a tennis racquet or golf club, some have reached a point where it is impossible to close an average sized hand around them. In my view this is overkill; you should have sufficient space to manoeuvre the shinai within your hand to correctly execute technique.
What has not changed is the guideline for measuring suitable tsuka to fit your own needs. You should place the tskuka of the shinai so that the tsukagashira rests in the crook of your right arm. You should then grip the upper end of the tsuka loosely with your right hand and your first finger should fit just below the tsuba.
If you are buying a new shinai and you have the luxury of choosing a tsukagawa to fit, you should have no problems. On the other hand if you have used a tsukagawa for a while it may have stretched. In this case you have to shorten it. There are two kinds of tsukagawa – toko and gin (gintoki). Toko is the cheaper kind and can normally be shortened by folding back the leather at the open end and making new holes for the leather thong that attaches to the tsuru. Gin tsukagawa are normally threaded at the tsuba end with a leather thong so they need to be cut at the closed tsukagashira end, and be sewn in a circle whilst turned inside out.