Let me level with you: a lot of levels at the stores aren’t actually level. If you use such a tool to hang a picture or mount a shelf to the wall, you’re not going to like the result. Today I’m going to show you how to test a level before you buy it.
What Makes A Level Level?
A level is just a glass vial, closed on both ends, that is mostly full of liquid, with an air bubble. There’s usually some reference marks on the glass to help you find the middle of the vial. If the vial is sitting on a level surface, the bubble will sit in the middle of the tube. If the surface isn’t level, the bubble will move toward the end that’s higher. There’s not much that can go wrong there.
The vial is mounted in a frame of some sort. And that’s where the trouble lies. The key to making the level actually level is that the glass vial has to be parallel to the frame. If not, you can’t rely on the tool. A truly level surface would show up as not level, because though the frame is parallel to the level surface, and therefore level too, the vial isn’t parallel to either the frame or the surface, and therefore reads as not level.
Worse, it isn’t even consistent. If you swap ends on the level, you’ll get a different result. A truly level surface would appear to be sloping to the right with the tool oriented in one direction, and sloping to the left if the tool is reversed.
How Can I Test Before I Buy?
I learned this trick in an excellent book: Shop Savvy by Roy Mountgoven. It’s a book I’d recommend to anyone setting up a shop.
Before you purchase a level, use it to check a store shelf, and note the location of the bubble. It doesn’t matter if the store shelf is level or not. Just note where the bubble is relative to the reference lines.
Then, swap ends on the level, and put it on the shelf in the same location.
If the bubble is in the same place (relative to the reference lines), as it is in the above pictures, the level is accurate, and it’s okay to buy.
I don’t have any non-level levels in my shop, so I induced an error in one so you could see the results. I put a bunch of masking tape on the bottom of one end of the level, raising that end relative to the other. So now the frame is effectively not parallel to the vial. Let’s see the results.
First measurement:
Then I swap ends:
It’s difficult to see the bubble positions in those shots, so here’s an overhead view through the little window in the top of the frame. First position:
Second position. You can easily see the difference in the overhead view.
What Can You Do About It?
Fancy levels include provisions for adjusting the vials to fix the problem. But most of the ones you’ll find in the big home improvement store lack such frills. In that case, set it aside and test another one. I had to go through five of the little yellow ones before I found one that was tolerably accurate.
If a level you own fails the accuracy test, see if it has a way to adjust it. If it does, fix it now, while you’re thinking about it. You’ll forget before you need to use it again. If you can’t adjust it, smash the vial and throw the rest of it away. You wouldn’t want to pick it up and use it by accident, so make sure you cannot.
Sherrey
Good to know