Create Your Own Cutting Diagrams
Kreg Tool Tips: Cutting & Measuring by
Kreg Tool Company
A good set of plans can be very helpful when building projects. Plans help guide us through the steps in the project, and, in many cases, they come with two very useful things: a materials list and a cutting diagram. The Certified plans on buildsomething.com are a great example. They include a materials list and cutting diagram that show how much material you’ll need, and where to cut each part from the boards and sheet goods.
What do you do, though, if the plans didn’t come with a materials list or cutting diagram? Or what if you’re designing your own project? In those cases, you’ll need to create your own. It’s easier than you might think. All it really involves is a few simple sorting and shuffling steps. Not only will it make your project easier, it will help you reduce waste, as well.
Make a Parts List
The first step in the process is to go through the plan or your sketches and make a list of all the project parts. Be sure to write down the thickness, width, and length of each part, and how many of each you’ll need. With that done, assign a letter to each part. Now you have your basic materials list.
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Sort by Thickness
Next, look through your materials list and separate the parts according to thickness. Make one chart for solid-wood parts and another for any sheet stock like plywood or MDF. You can use a format like the one shown here, listing the part letter and the quantity of each needed under the appropriate thickness.
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Sort by Width & Length
Now sort the list you just generated by width and length. Start with the thickest pieces and list these from the widest to narrowest. If you have a number of parts the same width, list them from longest to shortest. This step will make it easier when you lay out the cutting diagram.
Create the Cutting Diagram
The next thing to do is draw the parts on some imaginary boards and sheet goods. These don’t need to be perfectly proportioned, but be sure you draw them with the sizes of real boards in mind. Start with your thickest parts and draw on the widest and longest ones first. This way, you can fit smaller parts into leftover spaces in order to minimize waste. Be sure to draw in the correct quantity for each part on your list and label each one with the appropriate letter. Keep repeating this process until you’ve accounted for all of your project parts.
At this point, you’ll know how much material you need, and you can go shopping. Remember that your drawings don’t account for defects that you’re likely to find in real boards. Because of them, it’s a good idea to buy some extra—maybe 20-25% more than your cutting diagram calls for. You may end up with a bit of leftover material, but that beats not having enough lumber to complete your project. With sheet goods, by the way, this usually isn’t necessary.
Plot the Parts
With your materials and your cutting diagram in hand (whether you made it or it came with your plans), you might be tempted to start cutting. On projects with a lot of parts, though, it’s a good idea to recreate your cutting diagram on the actual boards. Just draw out each part using a piece of chalk and a ruler or square, and then mark the part letter. Don’t worry about sizing each piece exactly. You’re just marking them roughly to make sure that the pieces look good and that you have each accounted for. If you need to change something, it’s easy to wipe the chalk off with a damp rag and start again. You can’t say the same once the parts have been cut!
As you can see, creating a cutting diagram isn’t incredibly difficult. It does take some time, but it can save a lot of frustration and wasted material.