Cutting crown mould is often one of the most confusing things for a do it yourself homeowner or novice woodworker to attempt. The simple answer nearly every carpenter will tell you when you ask how to cut crown mould is: “upside down and backwards.” But without context it may not make any sense.
There are basically two methods used to cut crown. I will briefly describe both of them, then explain in more detail how each is performed and let you decide which is best for you.
The First method is to lay the crown on the saw just like it would be on your wall (but upside down and backward, I will explain later), then just make your miter cuts with the crown in place. This method is usually much easier for most after they understand the “upside down and backwards” instructions.
The Second method is to lay the crown flat and cut using a bevel, (the vertical angle), and a miter, (the horizontal angle). This method is often more difficult for many because the angles must be extremely precise and any incidental movement caused by vibration of the saw etc. can put the angles out and result in an imprecise joint. The fact that many rooms are not perfectly 90 degrees in their corners does not help and when adjusting for this deviation it is difficult to keep the angles precise or to reset them accurately after making slight adjustments. Also, crown mould comes in different angles (45 degrees and 52/38 degrees), making it more complicated when you try to figure out which angles to set your saw.
The First Method: Upside Down and Backward
The “upside down and backward” method is often the most used and easiest for most people to master, (it’s the one I use most of the time). The term “upside down and backwards” is actually very simple. If you look at the table and fence of the saw like it was the wall and ceiling of the room it becomes easier to picture. The fence of the saw is the wall of the room, and the table of the saw is the ceiling. So the saw is actually the room upside down. Most people start by putting the crown on the saw like they see it in the room. They put the detail, (the part that usually goes against the wall), on the table of the saw because this keeps it visually right side up, much like they see it on the wall. However, since the fence of the saw is the wall, you are essentially putting the crown upside down even though it looks correct compared to the room. A good way to get your mind used to the concept is to set your saw up so that your back is turned to the wall you are cutting the crown for. Take a small manageable piece of crown (about 2 ft.). Then, hold the crown up to the ceiling like you were going to install it, without turning it around, take it directly to the saw and flip it over. This is your “upside down” part of the term.
With your saw facing away from the wall you can cut your corners on the side they represent, the cut on the right side is for the corner on the right side (if you are still facing away from the wall). So if you turn around it will be the opposite (or…backwards!). When your saw is set up facing the wall for which you are cutting (or you are looking at the wall), you will have to flip the board over and turn it around to put it on the saw properly, effectively making it “upside down and backwards.”
If you have not completely wrapped your head around the concept of upside down and backwards, or have not done it enough to make it second nature then you will inevitably make a few bad cuts. It is always best to use a few scrap pieces to make sure your angles are right before committing to the actual pieces you will be installing. Once you get used to it and it makes sense in your head it will be very easy to use this method. Remember to use a crown stop or draw a line on your table and/or fence to make sure every cut is at the same position on the saw. If the crown is rotated slightly on the saw it will cut a different angle and won’t match up to your other miters (angles). Unfortunately you may not be able to use this method every time. If you’re the fence and blade on your saw is not tall enough to cut all the way through your crown you will have to lay it flat and use the second method. Generally any crown larger than 7 ¼ inches will not be able to be cut with a 12 inch blade.
The Second Method: Beveled Miter
This method is more complicated mathematically. If you are good with numbers you may prefer it. Also it requires a saw that will allow the blade to be set on a bevel. Sometimes this method is the only way to cut some crown, especially when your saw does not have a big enough blade to cut larger crown moulding.
The reason this method often found to be more complicated is because there is a fair amount of geometry involved. Rather than explain it mathematically, I think providing you with a chart would be more helpful. There are generally two angles that crown is milled for. The 45/45 and 52/38. I have provided charts for setting up your saw to cut either type. Remember that your angles on your saw may move slightly as you cut. You will also find that not every wall is exactly 90 degrees and may require some variation of your settings, (this is where it can get complicated), and when you change the position on your angles to cut each side of your piece, (or adjust for variations), getting back to the exact position you once had your saw can prove to be difficult.
When using this method it is very important to be as consistent as possible when setting your angles to cut. Any slight variations can throw your angles off by allot and your pieces will not match up perfectly. For this reason I prefer the “upside down and backward” method wherever possible. It allows for greater flexibility and the ability to adjust your angles more freely through experimentation by rolling the crown or just moving the one miter angle slightly. In this way you are not committing to each setting and having to constantly make adjustment changes to your saw.
Regardless of the method you come to prefer, the consistency of your cut angles is the most important thing to consider. Because you are cutting 2 sides on every angle, a miscalculation is doubled for each miter. However, once you get the hang of it, you will find that it becomes easier to judge the adjustments needed and you will be guessing the variations and making very accurate cuts with just your intuition. After you have mastered (or at least become comfortable) with how to cut crown mould, the next skill to learn will be how to cope crown.