When we’re talking about digital protractors, we’re not discussing the kind you used to use in school for geometry. A geometry protractor is used for measuring an angle drawn on a piece of paper. As such, it really isn’t limited to size or configuration. About the only limitation is it’s possible to see through the protractor to the lines on the paper>
Protractors used for carpentry work are used for measuring angles but these angles are on three dimensional objects. That limits the protractor quite a bit, as it needs to be able to fit inside or outside the angle. There is no integral means of determining the angle and in that sense, these tools are more a gauge than a measuring device.
At its simplest level, a carpenter’s protractor consists of nothing more than those two legs, with a bolt and wingnut to hold them together. To use them, the two legs are placed against the two surfaces making the angle and the wingnut tightened to lock them in place. Once removed from the location, the angle between the two legs is measured or transferred directly to the piece to be cut. The protractor can also be used to set up tools for cutting operations. Once the angle is measured, the digital protractor can be placed against the blade and table of a saw, allowing the angle to be set exactly.
While these digital protractors have everything simpler models do, they add a digital readout that measures and displays the angle formed by the two legs. This saves the step of measuring the angle of the protractor, while also increasing its accuracy. These digital protractors are a much more accurate means of measuring angles for carpentry, cabinetmaking, furniture making and general woodworking.
Digital protractors come in different lengths and generally speaking, it’s easier to get an accurate measurement when using a longer one. However, long protractors can be limited by the spaces they will fit in. For some types of work, especially furniture making, shorter legs on the protractor might be advantageous.
Besides size, the other major consideration when looking at a digital protractor is accuracy. While most units are more or less the same on this, low cost units might not be as accurate. Some low cost units have plastic legs, rather than metal ones, which could become more and more inaccurate over time.
Starrett has years of experience designing and building extremely accurate measurement equipment for use of machinists. The same level of quality and accuracy has gone into the manufacture of this protractor. If you are doing fine woodworking and need fine tools, this is the one for you. Read Full Review
I’ve picked this Starrett protractor as my number one pick because of their reputation for having provided machinists with high quality measurement equipment for years. This protractor provides the same level of quality and accuracy to both the contractor and woodworker.
The protractor works in a number of different modes, controlled by a simple three button control, a miter mode which reads out in actual saw readings, and a single cut mode for but joints. Bubbles for both vertical and horizontal directions allow you to measure an angle off of a vertical plane and the 360 degree swing allows you to measure any and all angles.
If you're needing a really big protractor, look no further. This digital protractor by iGaging has 24 inch arms, the largest on the market. It is special order only however, so you can't just pick it up in the store. Read Full Review
This is the largest digital protractor I know of, boasting a 24 inch edge on the front and 26 inch edge on the back. Both arms of the protractor are laser etched as rulers, providing both inch and metric readings while a hold function allows you to move the arms without losing your measurement. It will work for both inside and outside angles, with a measurement range of 360 degrees. Resolution and repeatability of the protractor are both 0.05 degrees, with an accuracy of plus or minus 0.2 degrees. The 24 inch protractor is a special order item, but they also have 12 inch, 8 inch and 4 inch models available.
Wixley makes the longest stock protractor on the market, with 18 inch arms. The edges of the arms are magnetized as well, making it ideal for use with metalworking. Read Full Review
The Wixey W418 is the longest stock protractor on the market and while not quite as long as the iGaging 24 inch unit, you don’t have to special order this one. Magnetized edges on both arms make it easier to get highly accurate readings when using the protractor for machinery or automotive uses. The protractor is limited to 180 degrees, not the 360 for the other models we’ve looked at, and it also has 0.1 degree accuracy and repeatability.
This protractor from General Tools & Instruments is a bit different than the others. The single arm design is centered on the head, making it perfect for transferring cuts to dimensional lumber. Read Full Review
General Tools & Instruments produces a number of different digital protractors models, most of which are the standard two arm design like the others we’ve seen. I’ve picked this one because if you need to measure an angle and then cut off the end of a board to match it, the head lays alongside the edge of the board handily for transferring dimensions. The single arm is six inches long, attached to the head, which holds an oversized display. Accuracy is to 0.1 degree within its 180 degree range and the display can be inverted for use when it’s upside-down.
If you're need a compact tool, than this three inch protractor from Wixley is for you. The smallest production digital caliper on the market, this one is ideal for use in tight places. Read Full Review
I’ve got to give Wixey credit, they have both the largest and smallest production digital protractors on the market. This little baby has arms that are only 3 inches long, making it perfect for really tight places and it has the same magnetized arm edges and digital head their larger digital protractors do. The resolution of the display is 0.1 degrees and both accuracy and repeatability are within one digit, with a plus or minus 0.1 degree tolerance.