Introduction: Make Your Own Precision Angle Finder

Picture of Make Your Own Precision Angle Finder

I always thought I wanted a precision angle finder. I finally decided to make my own. The photo shows it in use to check the angle of a rafter in my attic. This is a very easy project, but some precautions need to be followed to guarantee the accuracy of the tool when finished.

Step 1: Tools and Materials

Picture of Tools and Materials
  • A plastic protractor
  • A piece of wood
  • Some screws
  • A piece of wire or a long finish nail and a hex nut
  • Magnetic cabinet door catches (optional)
  • A table or radial arm saw
  • A rule (and a square)
  • An electric drill or drill press and bits
  • A countersink bit
  • Screwdrivers
  • Clamps
  • A file
  • A pair of pliers to bend wire, or a welder to weld a hex nut to a finish nail
  • A level
  • A grinder

The photo shows a commercially available angle finder. It reads 360 degrees. A protractor has readings for 180 degrees, but that will be no problem for a reason explained later. While the commercial version is not expensive, it is more fun to make your own.

(The photo is from

Step 2: Cut a Piece of Wood

Picture of Cut a Piece of Wood

I used a piece of 1 x 4 clear pine I had from another project. The two long sides must be exactly parallel to one another. I used a caliper to check. If you have a good table saw accurately calibrated, you should have no trouble. 

Saw your piece off to be a little longer than the base of the protractor, and so the corners are exactly square. Check with a good square and by measuring the diagonals. These things really need to be very accurately done, or the whole tool will be compromised.

The square is a larger tri-square I have long wanted. See this Instructable for how I made it.

Step 3: Clamp the Protractor to the Wood

Picture of Clamp the Protractor to the Wood

Once you are satisfied that your piece of wood has long edges exactly parallel and the corners are exactly square, rest the piece of wood on a flat surface. Place the protractor against it and let the protractor rest on the same flat surface. Gently clamp the protractor to the wood. Be careful that nothing moves during the clamping process.

Step 4: Fasten the Protractor to the Wood

Picture of Fasten the Protractor to the Wood

With the clamps firmly in place, drill and countersink for two wood screws that will hold the protractor to the wood. 

I chose to locate the screws at 45 degrees on each side of the protractor. Because they are countersunk, the screw heads are slightly below the outer surface of the plastic on the protractor.

I considered painting the wood white or placing paper under the protractor to make reading the angles easier, but decided it was not necessary.

Step 5: The Pointer

Picture of The Pointer

I planned to use a simple piece of straight wire with a round loop bent onto one end for the pointer or indicator. But, we moved a few weeks ago and I can not find that wire. I have a welder and decided to use it. My pointer is from a 2 1/2 inch finish nail with a hex nut welded to its head. Here you see a piece of 1/8 inch steel clamped in a vise. The head on the finish nail has been filed flat so it will stay in place easily. The finish nail and a #8-32 hex nut are held in place by spring clamps so I can weld the nut to the nail.

Step 6: Finish the Pointer

Picture of Finish the Pointer

I welded from both sides of the nut and ground the welding joints as flat and smooth as possible. I drilled the hole in the nut out to make a smooth surface inside. That is so it can swing on the smooth part of the screw in the photo as freely as possible.

Step 7: Attach the Pointer

Picture of Attach the Pointer

I drilled a hole at the center point as marked on the protractor. The hole in the protractor needs to be large enough for the shank of the screw. The portion of the hole in the wood needs to be a little smaller so the threads on the screw grab the wood. 

I placed a washer under the pointer. I did not make the head of the screw tight against the hole in the pointer, but made certain it is loose enough for the pointer to swing freely.

Step 8: Calibration Check

Picture of Calibration Check

Does the angle indicator show "0" degrees when resting on a level surface? I used a level, but the surface was not level. So, I placed a thin wedge under the level until the bubble was centered between the lines. (See the first photo. I turned the level end for end to be certain it was reading accurately, too.) 

See the second photo. The pointer is correctly calibrated. If the pointer did not read correctly, I could bend the nail just a little near its middle to get an accurate reading corresponding to the level.

Step 9: Using the Angle Finder

Picture of Using the Angle Finder

The first photo shows the angle finder in use to read the angle of a rafter in my attic. 

The commercial angle finder shown in step 1 is graduated with readings for 360 degrees. But, it does not have two parallel edges. I can place my angle finder under or over an angle to be measured. The first photo shows a reading taken from under that angle. The second photo shows a reading taken from above the angle. All you really need to know is how many degrees off of a horizontal or a vertical surface the angle is. The third photo shows the angle finder used with the side as the base for measuring a more vertical angle.

My angle finder does not have magnetic bases like the commercial version does. But, I could easily acquire some magnetic catches like those used inside cabinets to retain a door. If I put two on each side, I could attach my angle finder to a metal surface.


lbrito2 (author)2016-04-24


Phil B (author)lbrito22016-05-17

Thank you.

jubaernet (author)2016-02-14

excellent solution for finding angle. I am going to make one for myself.

Phil B (author)jubaernet2016-02-14

I used it again recently. I had a thought that next time I would make a square base piece instead of a rectangular base piece. That would make the same size resting surface, no matter the orientation. Thank you for looking and for your interest.

jubaernet (author)Phil B2016-02-14

I think that would be great. keep on posting sir. we need simple solution like yours. thanks in advance.

Phil B (author)jubaernet2016-02-15

Thank you. Most of the things I have posted solved a real problem I had. I never know what those will be. When I joined Instructables I thought I might possibly manage 25 posts. Somehow I now have a bit over 300 now. I am as surprised as anyone.

jubaernet (author)Phil B2016-02-14

I think that would be great. keep on posting sir. we need simple solution like yours. thanks in advance.

chrisjlionel (author)2015-07-20

Excellent work. I'll definitely make one.

pandibabu (author)2015-02-25

grgbpm (author)2012-11-26


Phil B (author)grgbpm2013-01-31


bricabracwizard (author)2012-09-23

I've just started doing 'angly' things and this is perfect for what I need - thanks!

Phil B (author)bricabracwizard2012-09-24

Thank you for your comment and thank you for looking. I am glad you can use this. I hope it works well for you.

veryken (author)2012-09-21

Nice job! I made something like this about 25 years ago. Much longer though. Now (for several years) I use the SmartTool Smart Level — practically every week to measure roof pitch at various job sites.

Phil B (author)veryken2012-09-22

I knew I could not be the first to think of this. It is only my version. Thank you for your comment.

caarntedd (author)2012-09-18

I'm making one of these.

Phil B (author)caarntedd2012-09-18

Thanks. I hope you enjoy it. I am finding uses I did not expect. You will, too.

bobzjr (author)2012-09-17


Beautifully done. Thanks for showing us. I've seen these before but never realized that the marker floats freely and points down automatically via gravity. I will have to make one of these!

Your work continues to add valuable insight. I look forward to checking more of your expansive body of work. I'm going to the center finder next...

Phil B (author)bobzjr2012-09-18

Thank you, Bob. I never thought much about how these angle finders work, but, my son-in-law has one several years old. The plastic for the body has shrunk more rapidly than the clear plastic for the dial cover and it continually falls off. Under the round label is a small steel axle pin. The red plastic pointer has a hole for the axle in the portion not visible. Then the pointer piece broadens into a pendulum of sorts. It works by gravity, too. About 5 minutes after I saw that I began to think about how I could make one. Thanks for looking at my stuff. I hope some of it is useful to you.

snideprime (author)2012-09-13

I also miss the days when PS and PM published DIY stuff and tips, instead of always which-is-a-better-buy articles. When I find a stash of old ones at a yard sale or thrift store, I buy them. I guess I'm just made for Instructables!

Phil B (author)snideprime2012-09-13

Popular Mechanics and Popular Science now have old issues archived on-line. It is fun to go back and read articles I remember. But, those articles are often dated. It would be great if a magazine today had the editorial philosophy of those magazines then and published DIY articles for today's needs and technology. One problem is that many things today are non-repairable throw-aways. Still, I learned how to use power tools and do various aspects of woodworking through those magazines. Thank you for the comment.

artworker (author)Phil B2012-09-13

Popular Mechanics! My dad used to bring those from the library! I loved those! Specially those projects that just used single board of ply! I wasn't allowed to use carpentry tools as I was around 8 then. I made miniatures of them using foam boards/paper. Please post the links to PDFs for old Popular Mechanics if possible!

Phil B (author)artworker2012-09-13

Popular Mechanics archives

opular Science archives

echanix Illustrated archives

he navigation procedures for each varies a little, but it is fairly intuitive.

artworker (author)Phil B2012-09-16

Thanks a lot!

Phil B (author)artworker2012-09-17

You are welcome.

Bill WW (author)2012-09-16

Nice, VERY nice.

This comment from an engineer who has almost every imaginable angle measuring device.


Phil B (author)Bill WW2012-09-16

Thank you for the comment. I actually used this little device in a project yesterday. My wife wanted her bicycle hung on the garage wall. I was using a flip down hanger with two arms. Those are designed to support a level top tube on the frame. She has a lady's frame with a very angled top tube. The bike would look like it was racing downhill. I made a dry fit by hooking one arm where the seat stays connect to the seat tube and hooking the other under the top tube. I needed to know how much the rectangular mounting plate was angled. I held my angle finder on the top edge of the mounting plate with my other hand and read 11 degrees. Had I guessed, I would have thought the angle might have been 15 to 20 degrees. But, her bicycle now looks level on the wall.

At one time I wanted to be an electrical engineer. Although it is not electrical and although it is not a measuring device, the outcome of this project pleased me very much because it represented a precise outcome using very minimal and common tools. If you have not seen it, you might very much enjoy it.

Bill WW (author)Phil B2012-09-16

Phil, I imagine your wife has been enjoying bicycling lately with the surprising dry warm weather we have been having in the NW.

Read your instructable about enlarging the arbor hole in the saw blade. Wow, that is a difficult task, having to get it perfect. Especially with the tools we have, and none of the precision tools in a machine shop. I'm doing a similar task now, trying to find exact center on some small parts. So much easier if we can start start from a center punch mark and work outward from there!


Phil B (author)Bill WW2012-09-16

The weather has been nice. My doctor found something nasty growing on my skin and removed it, so now I get to be careful about sunlight. As much as I enjoy riding my bicycle moderately long distance, I have been limiting my cycling to hours of darkness, which has its own limitations. People who have had such things growing on them often slop on the sunscreen and go anyway, but I really do not like that stuff. Enlarging the hole in the sawblade was not bad after I used my head first. It took a while to decide exactly how I would do it. It might not help, but did you see my Instructable on making a center finder?

chobbs1957 (author)2012-09-15

I'll be putting this to use. Thanks, Phil. Keep 'em coming.

Phil B (author)chobbs19572012-09-15

Thank you. Each time I do an Instructable I am sure I have used all of my ideas and it is the last one I will ever do. I hope you enjoy it after you make it.

dimtick (author)2012-09-14

like this. very simple.
when i first saw this, is I wondered if you could incorporate a laser pointer that would project straight down so this could be used as laser plumb bob. would be really useful for framing. using this tool you would have the bottom & top points and the angle for the top cut. simple matter to measure the distance between the points to get the board length.
thinking out loud if you could reverse the laser so that it would project up, you could use this to locate points on the ceilings or rafters. let's say your framing a half wall. you locate the wall on the floor. place the angle finder on the floor and project it up, mark the point, then use the angle finder to measure the top cut.
commercial laser plumb bobs are $100 and up and way out of reach for your average weekend handyman so having a simple version could be really useful

thought you might like to see this:
i did a quick search on instructables to see if anyone had made a laser plumb bob and found this. another clever application of your little angle finder along with some geometry to measure heights.

Phil B (author)dimtick2012-09-14

You have an interesting idea. For a lot less than $100 you can buy various laser levels. Either one of those could be mounted from a pivot, or the insides could be removed and repackaged to suit your needs. You would not even need to know the indicated angle, only where the laser beam falls.

rimar2000 (author)2012-09-13

Very good and interesting instructable, as always, Phil.

I did something like this when did my equatorially mounted solar cooker, unless instead of a hand, my pointer was a little steel ball inside of a soft clear PVC tube. The device was to set the parable's axis angle at local latitude.

Seeing the countersink with its note, I thought it would be useful for all we not anglophone a detailed "images and notes only" instructable with the tools and their names. Maybe somebody in the staff could do it. It could be a colaborative project, because surely some tools have different names depending the zone.

Phil B (author)rimar20002012-09-13

Thank you, Osvaldo. Many years ago Popular Science magazine had a feature called the "Wordless Workshop." Simple projects were described with a few cartoon drawings and no words.

blkhawk (author)2012-09-13

Very simple and practical idea. I remember doing something like this for elementary school, to determine the position of stars at certain times. Instead of the pointer it was a plumb. With some knowledge of trigonometry, you can even roughly determine the height of a building with this little contraption.

Phil B (author)blkhawk2012-09-13

Thank you for your comment. What you made in elementary school is almost identical to this and is called an astrolabe. I considered mentioning the astrolabe, but finally did not. A small weight on a string for an indicator would work here, too. I did search Instructables, but found nothing like this previously done as either an astrolabe or as an angle finder.

coolbeansbaby68 (author)2012-09-13

Nice Job Phil.....

Phil B (author)coolbeansbaby682012-09-13

Thank you, Jim.

coolbeansbaby68 (author)2012-09-13

Nice Job Phil.....

shazni (author)2012-09-12

Oh this is really good! I'm going to try it...thanks

Phil B (author)shazni2012-09-12

If you have a use for one of these, you will like it very much. Thank you for looking and for your comment, and for your rating, assuming you were the one to rate it.

shazni (author)Phil B2012-09-12

haha yes...only i rated 5 stars and it shows the stats..i guess it's the overall rating :-)

Phil B (author)shazni2012-09-12

Thank you, again, for the rating. The rating system is weighted somehow. Many "5" ratings are required before the rating number shown begins to approach "5." It is above my paygrade to understand this.

About This Instructable




Bio: I miss the days when magazines like Popular Mechanics had all sorts of DIY projects for making and repairing just about everything. I am enjoying ... More »
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