Accurate to the Nth Degree
Issue: Issue 3.23
Posted Date: 12/3/2002
Ellis Walentine, Michael Dresdner & Rob Johnstone
Q. I'm not really a beginner when it comes to woodworking, but I'm no expert either. Somewhere in between. As my woodworking projects become more complex, I'm finding that proper tool alignment is becoming much more important. I know how to align my tools, but my problem is finding or having a measuring device that I can trust to be exactly accurate. My speed square and my framing square are at odds with each other slightly when it comes to a true 90-degree setting. And I have an adjustable protractor that gives a slightly different answer that the other devices. So, in my mind, I can't trust any of them.
The project I'm working on now calls for 12 cuts at 30 degrees each. Thus, when all edges are joined, it will form a circle or a wheel. If those cuts are not exactly 30 degrees, I'm going to end up with a gap. Even a simple miter joint won't fit properly if the angles aren't exact. I need to be able to accurately measure and set angles of 90, 45, 30, 22.5, 15 degrees or anything in between. Is there a measuring device on the market that will accomplish this task?
Ellis Walentine: "My advice is to work empirically. In other words, make all your test cuts at one setting in scraps, and adjust the setting if necessary. Do this until everything fits perfectly, then cut the good wood. If you drive yourself crazy trying to lay out the angle perfectly, you're still going to have to set your machine to cut to that angle, which is another trial-and-error procedure. If you do a lot of the same angle cuts, it wouldn't hurt to cook up an adjustable jig for those cuts."
Michael Dresdner: "Yes, there are most certainly quality measuring tools on the market that are accurate enough to accomplish your task. I have both Bridge City and Starret angle measuring tools that are highly accurate, and these are by no means the only companies who hold to high standards. By the way, here is an area where you are quite unlikely to find a cheap tool that is accurate."
Rob Johnstone: " There are a few after market products that could help you get the settings that you need ... but the cut that you are attempting is a tough one. Among many others, Pacific Rack and Machine has several angle and depth setting devices which may help you out. Rockler has an ultra accurate miter gauge and Incra has an integrated system for accurate machining. You are correct in your assertion that you need to properly tune up and align your tools before you attempt working to such exact criteria. Good luck, and remember: in woodworking it is never a mistake unless you can't fix it!"