48" level accuracy

Old 10-04-21, 11:27 AM
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48" level accuracy

I'm looking at a new 48" bubble level. There are several features I've considered in the past but never accuracy. I noticed one inexpensive level has an accuracy of "+/- 0.0015in/in. (0.15 mm/m)" which got me thinking about accuracy. Looking online, tool websites recommend much more accuracy. Yet +/- 0.0015in/in seems more than sufficient for my DIY needs as I think the error rate would be only 0.0721" in 48". At what error rate does accuracy become important in a bubble level? BTW, when accuracy is critical I assume I'd need a digital level, anyway.
Old 10-04-21, 11:56 AM
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"At what error rate does accuracy become important..."
How good is your vision and judgement? That is the limiting factor since a bubble level relies on your ability to visually tell when the bubble is in the middle.
Old 10-04-21, 12:05 PM
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0.0721" in 48"
Thats a hair over 1/16" over 4 feet.

I doubt you could see that on the level and doubt there is any relevant construction that would need anything less!
Old 10-04-21, 03:04 PM
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A lot of the levels you find in box stores and hardware stores are pretty low quality and aren't always accurate. One good test is to simply try the level out in the store. Set it on the floor and see if it's level. If it is, flip the level end for end and check it again. Then flip it upside down and check it again. Then flip it end for end and check it again. On a level floor, a good accurate level should read the same no matter which way you flip it.

Not surprisingly, you might need to go through a few levels before you find one that is really dead on.

1/16" over 4 feet.
This is one big reason why I'm a proponent of 78" long levels for setting doors. You want a level to be dead on when setting doors and cabinets... And the longer the level is the more accurate you will usually be because every time you move a 4ft level you introduce that margin of error. The longer the level, the better. It's not only a level, it's a straight edge that can easily detect ANY bow in a door jamb.

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