Sunday, February 20, 2011

Adjustable Levels: What's Under The Hood?




I had hopes of making an adjustable, rather than fixed level, but after taking apart one of the antiques I bought, I see that I lack the necessary skills to do so.

This E. Preston and Sons level (foreground in the first image) includes plumb and level vials, each of which are housed in a "vial casket" (which sounds more like a shoddily constructed sarcophagus than it does an encasement for a spirit level).

The adjustment for both vials relies on a pinned hinge, spring, and machine screw.

The screw slides through the spring and threads into a tapped metal cup that supports the spring. By tightening or loosening the screw, the casket is pulled closer to or pushed further away from the brass top plate. 

It's a clever way to maintain the accuracy of the level. But how do you determine level in the first place?

Several commenters in the last post offered good suggestions. I had planned to find the most level surface in my shop by using manufactured levels and then shimming accordingly. Of course, who's to say that they're accurate?

Instead, I've decided to do as the Romans did by using a trough (in this case, a long glass baking pan), marking a line on each end at the same height from the bottom of the pan, filling it with water, and sitting it on a flat surface in my shop. Then, I'll shim as needed.

After that, I'll lay a large sheet of brass on top of the pan on which to place my shop-made level.  (A sheet of metal rather than wood because it's more likely to be perfectly flat.)

Old vials which did not have adjustment mechanisms relied on plaster to seat the vials.  I'm thinking of using silicone sealer instead because it will remain flexible as the wood expands and contracts with the seasons.

And speaking of vials, you may wonder where I got those two lovely glass ones at the top of the page. Thank you to my friend, Charles Davis, for sending these original, unused Stanleys to me.

They have black lines which help determine when the bubble is centered. Vials that did not have these lines required a center strip of brass on the brass top plate, which can be seen on the Preston level.

The glass vials that Charles sent are curved in a shallow arc to help the bubble find center.

Vials that were not curved made it nearly impossible to center the bubble. The most minute movement in the angle of the level caused the bubble to shoot toward one end of the glass or the other.

That's what I call a vial with a vile temperament.

15 comments:

Dyami said...

Sounds like you're on the way to making a nice level, Kari. I'm enjoying your new level obsession.

Al Navas said...

I think it is great you are staying on the level, Kari ;)

Al

DaveL said...

Kari,
You can check a level on a flat surface by turning it through 180°, it should read the same both ways. So shim it to show level, if when turned it still shows level it is accurate

N said...

to find level use a plastic tube say 10 feet long or so and make a 'u" shape with it, fill with water to within an inch or two of each end. Set your level even with the waterline and it will be level. Water always seeks it's own level.
Norm B

Darnell said...

What a great idea for a project, a brass bound beech level is now on my official to do list. I assume you're going to engrave the heck out of the brass. Do you have a design in mind? I've got an old Stratton Bros mahogany level with a turn of the century style eagle engraving that I think is beautiful.

TJIC said...

> . I had planned to find the most level surface in my shop by using manufactured levels and then shimming accordingly. Of course, who's to say that they're accurate?

You know how you check a square for accuracy by putting it against a reference edge (like your tablesaw top) tracing the tongue, then flipping it, and tracing the tongue a second time?

(This results in DOUBLE the error showing up as a gap between the traced lines).

You can do something similar with a level: shim it so it claims that its level, then flip it. You get DOUBLE the error.

If there's no error, then 0/2 = 0, and your level is accurate!

John Cashman said...

Flipping the level 180 degrees is how I've always done it. You don't even need to shim. As long as the bubble is off the same amount in the same direction after flipping end for end, the level is "on the bubble."

The Village Carpenter said...

Dyami, the next parts should be fun--excavating the mortise and cutting the wood to match the shape of the brass top.


Al, nice one. ; )

Dave, that's a much easier way to determine level. Thanks for the idea! My baking pan is now safe from my clutches.

Norm, thanks for the suggestion. Where do you get a tube like that? Is there a link where we can see this idea in action?

Darnell, I haven't learned how to engrave yet, so this one will be a little Plain Jane. I'd like to see your eagle engraving--is that on your FB page?

Thanks, TJIC. I'm glad that you guys offer other ideas—especially ones that are easier than what I came up with. :D

The Village Carpenter said...

Thanks, John. I toss these things out here in the hopes that you guys will offer good ideas and you never disappoint. :o)

Bill said...

Have you said (I may have missed it) why you need a level? Brick work? Building a house? Temperament adjustment? Or simply because.

The Village Carpenter said...

Bill, that's a great question. I'm building this level for several reasons: it's a fun and unusual project; I like fancy tools and saw a photo in a book of the one I'm making; I've been wanting to incorporate brass into projects and this seemed like an easy way to start; and, I thought that readers might find the project interesting.

The Village Carpenter said...

Ha. I guess I didn't really answer your question. Do I need a level? Nope.

Bill said...

Got it! I've made a thing or three for similar reasons. I wasn't certain that it was for commercial purposes.

John Cashman said...

This is definitely in the category of a shiny thing. We'd all like to think we were practical and pragmatic, but the fact is we all like shiny things sometimes. Heck, it's the rock upon which our economy is built. And a shiny thing that we've built with out own hands is infinitely more valuable than one we've simply purchased. That's why we're all here.

Anonymous said...

2-24-11

HI Keri,

“But How Do I Know When IT is Level?”

DAAAAA

The Power of Brain Storming!

The Water Level!!

A relative used to set up double wide mobile homes, and he used a water level. A 50 foot vinyl tube with water in it. I think that he used food coloring to tint the water for a better visual indicator.

Google “Water Level” and you will find more data than you will want to read. Or check on some of these links listed below.

In your reading you probably will come across the term “Meniscus”. This means that the water in the tube will “wick-up” the sides of the tubing. As an experiment, put some water in your glass Pyrex measuring cup and see how the surface of the water is concave. (Wicking up the sides.)

The opposite is Surface Tension of water, as when you can actually put water in your measuring cup that extends above the edges of the cup, and the surface of the water is convex.

Finally, you can’t go wrong with testing your new level by rotating it 180 degrees as explained by my fellow posters. Remember that you only need to take out one/half of the error. I’ve done this for years when calibrating the electronic compass systems on Aircraft leveling a transit for the compass calibration.

You are setting a wonderful example for this “want-a-be”.

Warmest regards
The Village Sexton

http://www.watrlevel.com/index.htm

http://www.buildeazy.com/fp_waterlevel.html

http://www.factsfacts.com/MyHomeRepair/WaterLevel.htm

http://www.deckmagazine.com/article/64.html