Half a dozen? 6? How did you get
that many?!
At best, you're looking at 10% of total club membership doing the majority of the work in most clubs. You can try different things to increase that but it all depends on the makeup of your club too.
If you have a lot of retirees with time on their hands, then you might have an advantage with getting those folks to help, for example. Retirees are no guarantee, though. I've specifically been told, in various clubs and other organizations, from retirees something like ... "I have no interest in a position of responsibility. I'll help as needed but I'm not going to be responsible for anything."
Unfortunately, you're likely to get your best help from either...
1) Members with something to prove or with motives of getting something else from the club.
2) Younger and/or members new to woodturning with a burning interest in it and sharing it. These, quite often, burn out quickly (within a couple of years at best) and you might be left with a void once they come to their senses.
Things that have been suggested before are...
1) Making participation a requirement for membership. You have to help plan, schedule, etc. at least X number of club activities per year. Obviously, this has varying levels of support and good/bad feelings with clubs. But, it can be tried at least in part. See if it works for you. It has in some clubs.
2) Simply ask. All to often, we expect others to have the same level of committment or interest or "take-charge" attitude as some others. Asking, usually in a straightforward way and not just a general "Hey, who would like to help with...", will yield some good help. Directly asking for help, individually, has helped but it's not a sure thing.
3) Give incentives for those that do help, plan, etc. We're not talking about just a nod to them in the newsletter or website or mention at the meetings. Give gifts, priviledges, exposure, lessons and so on. Give real benefits. For instance, for helping demonstrate at club demonstrations, I've given lessons to club members in one thing or another. Even gave a lesson on the skew for a few hours to a member AT the public demonstration. It went very well for all involved including the public watching it all.
Just a few things to try among others I'm sure you'll get here...
There are some very notable exceptions but you are experiencing the norm. Many people will chip in if you approach them individually and ask for them to do a specific task. Otherwise I can't offer any helpfull advice.