Then you can read the scale for the miter cut which is the angle bisected, or dived in half. I need to make a 3 sided box out of crown molding and I don't know how to figure the angles.
If you open the above image you will see the protractor angles set onto a miter saws table.
But the angles on a miter saw gauge are off 90 degrees to the angles on a protractor, which causes a lot of confusion.
Miter saws didn’t always come with miter saw gauges that were set 90 degrees off from protractors. The easiest way to solve this whole problem is to use a Sharpie to mark your miter saw gauge with protractor numbers.
Jesper enjoys SCUBA diving, mountain biking, and especially photography, which he practices in his free time.
I usually subtract the reading on the protractor from 180 degrees and bisect the difference.
At this point in my career as a fine trim carpenter or any of the guys work for me can’t figure it out with out the tool telling them what to do it becomes time to hang up the tool belt. Unless of course you are one of those mystical wood wizards who NEVER had to learn ANYTHING from ANYBODY. Fred, you suggest that you need no reliance on tools to calculate and cut angles in wood, right? I kinda like what Jesper’s done with his saw though, putting the correct angles onto the saw scale, that could save me time. Hmmm…no one mentions coped corners, which will forgive several degrees out of square. This debate has been going on for years, and why I was interested in a Festool Kapex, as overpriced as it is. As a basic article I think it is more important to teach the proper methods, not add crutches. I am not a contractor, just a semi handy homeowner who enjoys learning new carpentry techniques. On the job site today we all had an awakening when we took the time with the saw and what you described.
Jesper,I was looking for an easy way to learn how to miter the baseboards for our basement. Not a pro, but I’ve installed over $6k of millwork in my house, and used a vintage Stanley No. Consider this explanation: The outside most (or lower if you prefer) scale shown on most miter saws starts at 0 degrees in the center. As Jesper pointed out, the scale on the older miter hand saw box starts at 90 degrees in the center and decreases to either side. Here’s a picture of my Incra miter gage that has both reciprocal scales as Jesper’s mark up showed. As you can see from the 1 degree marks between 50 & 45 degrees on the lower scale, the yellow line at 47 degrees points directly to 43 degrees on the upper scale. My Swedish carpenter grandfather used to tell me that Loki the Norse God of tricks invented the zero centered scale to confuse every one. Lots of carpenters have trouble understanding angles–primarily because of the miter gauges on miter saws. I like to bisect angles with a bevel square and compass, and, if the angle is obtuse; then, I subtract from 90 degrees by marking the bisected angle on the back side of a scrap of flat stock, flipping it over, and finding the angle by swinging the saw blade to the line, right?
As shown, I clamp a workpiece to the perpendicular fence, slide the whole assembly to the line of cut (reason why I use a spring clamp), and then cut safely the acute angle. An alternative to using a clamp to hold the workpiece to the perpendicular fence is adding a backer board between the fence of the saw and the back fence of the jig (shown on photos 1-2-3-6).


I am in the process of building a garden implement shed for my wife and I wanted it to have some natural light.
That’s a interesting solution to acute angles and perfect location to build your shed. Thanks Jim, after making the first cut using the jig I felt safe cutting those acute angles. DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ.
There are many times that I find I need cut trim or molding at an angle greater than my miter saw was designed for.  Most miter saws cut to 45 degrees or slightly larger, usually 50 degrees. But what if you need to cut 55 degrees or a greater angle?  Cutting Acute Angles means a greater angle and one that miter saws can not give you without assistance. One very dangerous way is to hold the piece to be cut perpendicular to the saws fence and freehand this cut. The goal here is to make an auxiliary fence jig that can be clamped or screwed to my miter saw fence. Once the jig is secure the trim is held tight to the jig and the saw can be adjusted to much greater angles than if you used the saws fence. Most table saws are set with the 90 degree as 0 degrees, so if you add to the angle on the saw, you need to get to 90. On a cabinet for example, the angle is actually typically a 135 degree angle rather than a 45.
Finish carpenters are always bisecting corner angles—which is easy to do with a protractor.
Back before framers used miter saws, finish carpenters could use a protractor to read corner angles without any confusion.
He grew up in family homes in both Sweden and Denmark until the age of 18, when he moved to Los Angeles, CA.  He has worked in the construction trade for over 10 years, gaining experience in everything from movie sets to tile installation.
He is currently a Project Manager at Millworks By Design, a finish carpentry company located in Agoura Hills, CA. Recently married, he and his wife, Julia, spend their vacations traveling Europe and visiting castles, museums, and other historical sites.
Seriously Fred, look back at your comment and tell me WHAT it contributed to the discussion of the article content. Where it really gets interesting is those very acute angles at the ceiling where you have to run large, often multiple piece crown and coping is not an option. Some miter gauges run from 0 and some from 90, know the difference and how to deal with it.
I am a retired engineer and understand complementary angles and such but an article that puts it into simple perspective is a great help. That scale always shows the angle left on the board and that’s why trim carpenters were never confused by it.
Maybe it’s easier to remember the upper scale as the angle-angle-on-wood scale and the bottom scale as the angle-the saw blade-travels scale. After you have one comment approved, all of your subsequent comments will appear immediately. This way the workpiece rests against this backer board, which prevents the saw blade from catching and kicking it towards the back. Sign me up for free emails from Fine Homebuilding with the latest news, tips, and techniques.
He was running base around a series of odd angles -- angles he couldn't readily cut with his chop saw. Neither the service provider nor the domain owner maintain any relationship with the advertisers. All of the cuts made to that rafter—the ridge cut, the plumb cut, and the birdsmouth are all measured off the BACK of the rafter—off 90 degrees to the angle of the roof.


But I prefer to have the guys on my crew use a standard protractor, so they’ll know at a glance the difference between an acute angle and an obtuse angle. But when you set your saw at 43 degrees and cut the piece, the miter is NOWHERE near close! He often draws inspiration for his finish carpentry work from classical architectural details that he has photographed in cities throughout Europe, such as Paris, Rome, and Seville.
I’ve tried several different gauges, yet it always seems to come down to several test cuts to find the right compound angles for the right fit. Any time you can use a bevel gauge to get close that’s good but all of gauges that translate or marking it on your saw is just a way around understanding and knowing your craft and tools.
The upper scale starts at 90 and decreases angle wise from there (both sides) it’s the scale that tells you the angle left on the board. After some thought he assembled a jig similar to the one shown in the drawing.Use clamps or screws to secure one of the jig's fences to the saw's fence.
The gaps in the walls usually let in plenty of light….lol We seem to be doing lots of projects for the women in our lives here lately dont we?? In case of trademark issues please contact the domain owner directly (contact information can be found in whois). I wouldn’t expect an oil change worker to be able to put on a timing belt with out training. Some of our readers will be drawn to the OTT articles, like drawing and carving a volute; other readers will be more interested in how to cut miters in casing! I use it mainly to check corners when running base and crown to see how far off the corner actually is.
My mitre saw is on a job site so I can’t play with to see if I can figure out what you are saying. So instead, in order to make sense and help yourself in the future, stop identifying angles by the gauge on your miter saw. I used to do that on the tablesaw but each time I got several cutoffs flying around my head.
Clamp the workpiece to the jig (block under the far end of long pieces) and you're all set to cut accurate acute angles.M. I understood this at my job and helped the kids learn and that kindness of teaching and sharing the knowledge gets passed on. I often see trim work in people’s homes that was done by someone who does not know of this technique. I found years ago to get in the habit of setting the saw a tad over 45 for these and it usually worked out well. Those 2 angles always add up to 90 degrees, so the angles are always the reciprocal of one another. On his website, Rob uses his knowledge and experience to help and educate on best practices in the remodeling industry. I don’t cut rafters that often, so I usually lay them out with a framing square and then transfer the angle to the miter saw. That lower or outer scale always describes the angle the saw head swings through, which is NOT the angle left on the board if you were to measure it with a protractor, that scale is the reciprocal of the angle left on the board. Subtract 90 degrees from any angle measurement on your saw and you’ll have a true protractor angle.



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Comments to «Miter saw acute angle jig»

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