#5 blades will give you a very loose fitting puzzle. Make sure your locks have really good necks and it will be ok - especially for kids.
#3 blades will be tighter but still loose.
To get the tight fitting puzzles you have to use some sort of puzzle blades. 2/0, 1/0, or ones just made for puzzles. The problem is that the little buggers are wildly temperamental. I tried four or five kinds before I found one that I could control on my saw (Superior Puzzle from Mike's Workshop). Even then they can sometimes act like they're drunk. Instead of the usual 3-5 degree offset they can cut at up to 45 degrees off the apparent line of cut.
Some tips for puzzle blades I've painfully accumulated:
Don't even bother trying to cut with a fresh, sharp blade. You can slow your saw's speed way down and get more control but you'll still be fighting it for a bit. I keep bits of scrap about 3" long and when I go to a fresh blade I cut a thin strip off of one edge to take that super-sharpness off the blade. Sometimes I still slow the saw a bit for more control for the first few cuts. And I'm using 1/4" rather than 1/8".
Go slow. No, slower than that. Any time you're trying to have control slow your feed rate down until you actually have control.
Remember the standard scroll saw advice: no one but you knows the line you intended to cut so just do your best to make sure the line you actually cut looks ok. The key is to never let your lines cross or even touch. I sometimes get a little closer to another line than I want - that's one place the 1/4" is nice because it's a much sturdier piece at that thickness. Also, with 1/4" you don't have to put sacrificial layers around your puzzle. You do have to sand the back when you're done though.
A puzzle blade in good shape slides through the wood like a hot knife. A brand new blade shoots through like a red-hot chainsaw through butter. As the blade dulls it slows down - it's like the wood gets stiff. You can go until the blade breaks - just cut back from the other direction and try to match up neatly. I change blades when they break or when it gets dull enough I start to lose control.
Go on YouTube and search for Mark's Custom Puzzles. That's Mark G. Cappitella, the gentleman Steve posted some videos from. He's got a ton of videos that will teach you almost all you need to know about puzzle making. Some stuff he just knows so well after 25 years he doesn't think to mention it, some is stuff you just have to learn for yourself.
Puzzles are fun to do, but kind of a pain. Scroll-Right.com is my landing page on the way to my Etsy shop that has some background info for those interested.
KCSteve :->
