![f0044-01.jpg](https://article-imgs.scribdassets.com/30nphqmveoarrhz2/images/file8P0MCVZZ.jpg)
I’ve been developing a prototype launching device for small powerboats lately, and it has involved cross drilling rather a lot of aluminium tubes. (Note to self – must learn to weld aluminium!).
Anyway, I’ve always struggled with cross drilling tubes perfectly plumb. There’s something about