Tips For Making Cabinets Square With A Circular Saw

Reader question on how to get square cabinets when cutting plywood with a circular saw and what to do when your cabinets aren't square. A lot of good information on how to buy a circular saw for cutting plywood too.

A couple of days ago I received the following email from Catherine regarding cabinets that aren't square.

Hi,

I just found your site and love it. I'm new to woodworking and want to know what tools you use keep boxes square? I see a lot of 90 degree clamps out there and wonder if you recommend any of them? Also, what do you do if your project isn't square? How can you adjust it? Say a cabinet or bookcase for example.

Thank you, Catherine

In a follow up email I found out she's cutting her plywood with a circular saw and guide with pocket screw joinery. Since this is how I also cut my plywood I'm very familiar with the problems. There are four main problems that can cause your cabinets to not be square. In this article I'll discuss what causes cabinets to not be square as well as how to prevent them. At the end I'll discuss what to do when things don't line up square.

I had planned to write a separate guide on how to buy a circular saw but Catherine's question brings up a lot of the points I wanted to address so I'm including that here.
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How To Build Drawer Boxes

Everything you need to know to build drawer boxes for your woodworking projects in this drawer building tutorial.

Drawer box construction can seem daunting but there are only a few simple measurements you need to take to get the right drawer box dimensions. Using pocket holes joinery, plywood and the right hardware makes building drawer boxes easy.

When I first tried to learn how to build drawers for one of my projects I had a difficult time finding all the information I needed. After researching the topic and now having had some experience I thought it would be nice to outline everything you'll need to know in one place.

What You'll Need

Materials

• 1/2" or 5/8" plywood for sides
• 1/4" plywood or tempered hardwood for bottoms
• (8) Pocket Hole Screws per box

Tools

• Table saw or circular saw with guide to cut plywood
• Router, table saw or circular saw with guide to cut dados
• Miter box, power miter saw or table saw to cut to length
• Kreg Pocket Hole Jig
• Drill
• Tape measure
• Straight edge

Step 1: Drawer Box Construction Overview

Before we get into the details let's take a look at a typical drawer box construction. There are many different ways to build drawer boxes, some require special tools and skill while others are are very simple but not very strong or attractive. I think that using pocket hole joinery for drawers achieves a great balance between strength, appearance, cost and ease to build. That is the method I'll be describing.

Below is an image of an assembled drawer box minus the drawer slide hardware.

Using a separate drawer box and drawer front makes it easier to construct the drawer and provides more flexibility when aligning the drawer front on the cabinet.

The drawer consists of 6 main components. The drawer box sides, front and back, the drawer box bottom, the exposed drawer front and the drawer pull. 2 wood screws are used to secure the drawer front to the drawer box, 2 machine screws hold the drawer pull in place. Not visible are 8 pocket holes and screws that attach the back and front to the sides. The bottom sits in a dado (groove) cut into the sides, front and back.

Here is an exploded view of the drawer to give you a better sense of how it is constructed.

Step 2: Choosing Wood For Your Drawer Box

Before anything else, we need to determine the type of wood we'll use for the drawer sides and bottoms.

For the drawer sides your options in order of best to worst are: solid wood boards, veneered hardwood plywood, MDF and melamine coated particle board. Because drawers tend to get abused a bit I prefer to use plywood for drawer construction as it's more durable than MDF or particleboard. Solid wood boards are nice but usually overkill and much more expensive. I like PureBond 1/2" Maple Plywood because maple has a tight, closed grain and the light color is good for drawer boxes. PureBond is also formaldehyde free.

Drawer box side thickness should be at least 1/2" but if you can find 5/8" plywood your boxes will be stronger. Unless you're building large drawer boxes for very heavy items or large file drawers 3/4" sides won't be necessary.

For the drawer bottoms solid wood boards haven't been commonly used for many years for most drawer construction because of cost. 1/4" thick plywood is good enough for most drawers. PureBond 1/4" Maple Plywood is great for drawer bottoms. Another good choice that is about 1/2 the cost is 1/4" Tempered Hardboard. Tempered hardboard is dark brown and not as attractive as plywood but is strong enough for drawer bottoms, easy to find and cheaper than plywood. From what I remember it was used for the drawer bottoms at labs in scool.

Step 3: Drawer Box Width

There are two main factors that will determine the outside width for your drawer box, the width of the opening the drawer will be installed in and the side clearance required by the drawer slides you are using. 

I like to measure the opening width after I construct and finish the cabinet carcass. Sometimes things don't always go as planned and plywood thickness can vary. By doing this I get a more accurate measurement. I measure not only the front but also at a point in the back and use the smallest measurement if they differ. This is important because with many drawer slides there is very little tolerance.

Standard epoxy coated drawer slides (like the Blum 230M Epoxy Coated 3/4 Extension Self Closing Slides pictured right) need a 1/2" clearance on each side of the drawer box. The clearance requirements should be available through the slide manufacturer.

To determine the outside dimension of the drawer box take the inside opening measurement and subtract 2 times the side clearance.

In our example the opening width is 12", 2 times 1/2" equals 1" so our final outside drawer width will be 12" - 1/2" - 1/2" or 11".

Some people like to also remove an additional 1/16" from the outside width because the drawer slides do have some tolerance and it's easier to shim the slide if necessary than to remove material but I do not do that. The reason is that plywood tends to be a little bit thinner than advertised and the way I measure and build my drawer boxes already makes them come  out a little bit narrower than the actual measurements. I'll explain it more further down.

Step 4: Drawer Box Height

There are two situations you might run into when trying to determine the height for your drawer boxes. One is where there is a constrained height for the opening where the drawer will be installed such as the top drawer of a european style cabinet or drawers installed into face-frame cabinets.

Constrained Height

When the height of the drawer opening is constrained it is important to measure the actual opening dimensions. I do this after the cabinet carcass has been assembled and finished. I also measure both sides and in the case of any slight discrepancy I use the smallest measurement. Next it is a matter of allowing for proper top and bottom clearance as detailed in the specifications for the drawer slide.

Standard epoxy coated slides need a 1/4" bottom clearance and some top clearance to allow them to be more easily removed. I subtract 1" from the opening height to allow for the 1/4" bottom clearance and 3/4" top clearance.

In our example the opening is 5-1/2" so our drawer box height will be 5-1/2" minus 1/4" bottom clearance minus 3/4" top clearance equals 4-1/2" height for the drawer box.

Non Constrained Height

In some cases you may install drawers into a cabinet where there is not a separate opening for each individual drawer, such as the bottom portion of a european style cabinet. 

In this situation the drawer front height should already be known and I make the drawer box height 1-1/4" shorter than the drawer front. In the case of a 10" drawer front height, the drawer box height will be 8-3/4".

Step 5: Drawer Box Depth

Determining the appropriate drawer box depth is a little more complicated than determining the other drawer box dimensions. To get the best use out of the drawer the main driver for the depth of the drawer box will be the size of the drawer glides you use. For example, if you're using these Knape & Voigt 22" Economical Full Extension Drawer Slides you'll want to make your drawer boxes 22" to get full advantage of the full extension feature. Figuring out what size drawer slides to buy will be determined by your cabinets construction and size.

First you need to measure the inside depth of your cabinet where you'll be installing your drawer. Measure from the back of the cabinet to the front of the cabinet as shown.

If you're cabinets will have overlay drawers, where the drawer front sits in front of the cabinet body as pictured above, take the measured depth of the cabinet and look for a drawer slide that is 1 to 2 inches shorter than that measurement. The size of the drawer slide you selected will determine the length of your outside drawer depth.

If you're cabinet design calls for inset drawers, where the drawer fronts will be installed flush with the front of the cabinet, then you need to account for the thickness of the drawer front. In the above example we'll have a 3/4" thick inset drawer front installed in a cabinet with a depth of 16". That means we'll be looking for a drawer slide that is an inch or two less than 15.25" and build our drawer box depth so it matches the size of the drawer slide we'll select.

Step 6: Length of Drawer Box Sides, Front and Back

Now that we've determined what the outside dimensions of our drawer box should be, we'll need to figure out the length of each piece that makes up the outside perimeter of the drawer box. In the example we've been using we've determined our drawer box dimensions are 11" wide, 15" deep and 4-1/2" high.

Before we continue let's have another look at an assembled drawer box for reference.

Drawer Box Sides

As you can see from the illustration the length of each drawer box side is simply the overall outside dimension of the drawer box. In our case, 15".

Drawer Box Front and Back

Because the drawer box front and back fit between the sides it needs to be shorter than the outside width of the drawer box.

To determine the length of the front and back pieces take the overall outside width of your drawer box and subtract 2 times the thickness of the side pieces.

In our case we're using 1/2" plywood and our desired outside width is 11" so the length of our front and back pieces will be 10".

I mentioned earlier that the side clearance for the epoxy drawer slides are not actually 1/2" but 1/2" + 1/32" (17/32"). I don't account for the extra 1/16" (1/32" for each side) because plywood tends to be thinner than marked by about 1/32".

You should verify the thickness of your plywood with something like a Neiko 6-Inch Digital Caliper. Standard tape measures don't have markings down to 1/32" but if you don't have calipers you can stack 2 side pieces on top of each other and measure their combined thickness.

Step 6: Layout and Cut Drawer Box Sides, Fronts and Backs

I like to reduce waste when cutting lumber as much as possible which is why I always mock up my cut plan before hand. Buying one less sheet of plywood can be the difference between a DIY project that saves significant money and one that doesn't. I include the cut width (kerf) in the plans as well so I don't wind up with an unexpectedly short piece.

For most projects you'll be building multiple drawer boxes so the following cut plan is laid out for 2 of our 11" x 15" x 4-1/2" drawer boxes. It consists of 2 10" backs, 2 10" fronts, and 4 15" sides cut out of a 2' x 4' sheet of 1/2" plywood. 

I think the drawer boxes look nicer when the length of the piece follows the grain of the plywood which is why I layout the side pieces along the long end of the plywood. I make my rip cuts first and then trim to length with a power miter saw. I always make sure there are a few inches at the end of each ripped piece in case I need to extend the length of any of the components for some unforseen reason.

Dado

The bottom of the drawer box fits into a dado (groove) cut into the bottom of the side, front and back pieces. It does not get glued into place but rather floats in the groove to allow for expansion of the wood.

Since we're using 1/4" plywood for the drawer bottom our dado needs to be 1/4" deep and 1/4" wide. The dado should be cut a minimum of 1/4" from the bottom but if you want a stronger drawer box for storing heavier items space the dado 3/8" or even 1/2" up from the bottom.

How we plan to cut the dado will determine how we proceed cutting the drawer side components.

If You DO Have A Table Saw Or Router

A table saw is the best tool to use to get accurate, repeatable rip cuts for the drawer side components. You can also use it to cut the 1/4" dado or you can use a router table or router with guide. If you don't have a table saw but you do have a router you can rip the plywood with a circular saw and guide then cut the dado with the router. In either case the procedure is the same.

1. Rip the long 4-1/2" strips of plywood using either your circular saw and guide or table saw.
2. Cut the dadoes using either your table saw or router.
3. When it's time to assemble the drawer boxes trim the pieces to the correct length using a miter saw.

If you don't have a table saw or router and don't want to buy one but you do have a Dremel rotary tool you can use it with a guide and a Dremel 654 1/4" Straight Routing Bit. Using it along with this Dremel 231 Shaper/Router Table makes it easy to make consistent daos in the drawer. The bits dull fairly quickly so you might want to pick up a spare and remember to feed the drawer side slowly and make 2 or 3 shallow passes instead of trying to cut the full depth of the dado all at once.

If You DON'T Have A Table Saw Or Router

If you don't have a table saw or router with a router table or guide don't worry. You can still cut out your drawer box components provided you have a circular saw and circular saw guide. The order of your cuts will be slightly different.

1. Mark out all your cut lines on the plywood. This includes both edges of the dadoes and don't forget to account for the cut width (kerf) of your saw blade when measuring out multiple rip cuts. Mark the cuts so you know which lines represent the dados and which lines represent the rip cuts. Each cut should have 2 marking lines, one for each side of the cut. Using different colors might help. See picture to right for details.
2. Set your saw blade to only cut 1/4" deep into the plywood. Test it out on a scrap piece to be sure you're not cutting too deep.
3. Lay your saw guide along each dado and cut out the dado with your circular saw. Take your time. Depending on the kerf of your saw you may need to do 1 or 2 more passes to get the desired 1/4" width. It's easier to cut all the dadoes before ripping the strips.
4. Set your saw blade to cut through your plywood and proceed to rip out the strips for your draw sides.
5. Use a miter saw to cut the components to length when it's time to assemble the drawer boxes.

I've done this before but it's very important to lay out each side of the cut accurately and take your time setting up your saw and guide so you don't mess it up.

Step 7: Assemble Drawer Box Sides

With all the drawer box sides cut we can now begin assembling the drawer box.

Start by drilling 4 pocket holes on the front and back pieces using a Kreg Pocket Hole Jig. The pocket holes should be drilled on the side opposite where the dado is cut. Make sure you don't drill a pocket hole over the dado. For larger drawers you may require additional pocket holes. Pocket holes should be no further than 6-8" apart.

Once the pocket holes are drilled, screw the drawer box together as shown.

Make sure that the drawer box dimensions are correct and that the box is square before proceeding. If not make any necessary adjustments.

Step 8:  Cut and Install the Drawer Bottom

With the drawer box assembled we can take final measurements so we cut the drawer bottom precisely.

Measure the inside dimensions of your finished drawer box and add 3/8" to each dimension. This allows a little room inside of the dado for expansion.

In our case our inside dimensions are 10" x 14" so we'll need to cut a 10-3/8" x 14-3/8" rectangle out of our 1/4" plywood. I like to cut it so the direction of the grain runs from left to right when installed in the drawer but this isn't that important and will cut in either direction if it makes more efficient use of the plywood.

With the drawer bottom cut to size unscrew the pocket holes from the back of the drawer box and carefully slide the drawer bottom into the dadoes on the drawer box sides. 

Place the drawer box back in place and make sure everything still fits correctly and the drawer box is square. Screw and glue the drawer box back together and your drawer box is now complete.

Step 9: Finishing

Before going on to finishing, if you have a router you can ease the edges of the top of the drawer box sides with a round over bit or aggressively sand it to get rid of the sharp edges. 

Sand the drawer box with 80 grit, then 120 grit sand paper to smooth out any rough spots or tool marks.

Staining drawer boxes usually isn't necessary but a polyurethane coating will help protect the drawer box and keep it clean. Avoid using oil based sealers on drawer boxes because they can out gas for years and that's not something you want in an enclosed space like a drawer. For drawer boxes I like to use Minwax Water-Based Polycrylic.

All that's left to do is install the drawer slide hardware in your cabinet, position and attach your drawer front and drawer pull.

Which Kreg Pocket Hole Jig To Buy

Almost all woodworking projects require joining two pieces of wood together. There are a number of different joints that can be used to create a strong connection between 2 pieces of wood but the easiest and most affordable way for the DIYer is to use pocket hole joints. Kreg makes the most popular pocket hole jig on the market.

Kreg makes a number of different pocket hole jigs that range in price from very cheap, to somewhat expensive. This post will help you decide which Kreg jig to buy.

Why Pocket Hole Joints?

Pocket screw joinery is the best option for the do-it-yourselfer because pocket screws create very strong joints and don't require you to have a lot of special or expensive tools that you won't use frequently.

Dowels, biscuits, half lap joints, dovetaills, and so on are time consuming and sometimes require specialty tools. If you're not a full time carpenter and just like to build things from time to time because it not only saves money but it's fun, it's important to not spend a lot of money on tools that will collect dust. All you need are butt joints which are easy to cut even on a small budget. See my post on how to make square cuts. Getting perfectly square cuts will ensure a straight project and strong joints.

You don't need dozens of clamps! The screws will hold the work pieces together. Clamps aren't cheap and even small projects wind up needing more clamps than I have. I built a number of euro style cabinets to make a built-in desk and I don't own a single expensive, long bar clamp!

How Strong Are Pocket Hole Joints?

Pretty strong from my experience. I haven't done any formal testing but the first thing I built with my Kreg Mini when I got it was a pair of panel carriers to move some drywall and plywood down to my basement. We were moving 2 sheets at a time, about 104 lbs, down the stairs. About half the time using the top handle with the pocket hole joint. About 2,000 lbs of drywall and plywood was moved this way. That was about 3 years ago and I've used them a few times since and they haven't failed. Cabinets, desks, and all other projects I built with Kreg pocket holes have been very sturdy too.

Kreg Mini Pocket Hole Jig

The Kreg Mini Kreg Jig Kit only costs around $20 and is a good pocket hole jig to have even if you have more expensive Kreg Jigs because it can get into spaces others can't, like under stairs to make repairs and into tight corners. If you already own another Kreg Jig you can save some money buy just buying the Kreg MKJ Mini Jig by itself without the accessories.

The accessories that come with the Mini Kreg Jig Kit are a special stepped drill bit that makes the pilot hole and pocket hole in one step. The bit comes with a stop collar and an 4mm hex key for adjusting the collar.

The Kreg Jig Mini makes the same pocket holes it's big brothers make. This is the only Kreg Jig I own and I've used it for numerous projects including cabinets for a built in desk. I learned how strong the pocket screws were when I moved dozens of sheets of drywall with my DIY panel carriers.

It's a little slower to use than the other jigs because you have to manually place the jig in the correct spot. Using makeshift spacers made it easier and using the Kreg Face Clamp speeds things up even more. You can get a Vise-Grip Locking C Clamp with Swivel Pads for about half the price but the Kreg Face Clamp has larger pads which will minimize the risk of putting dents in the wood.

Kreg Jr. Pocket Hole Jig

In hindsight, I should have bought the Kreg R3 Jr. Pocket Hole Jig System vs the Kreg Mini. It's only about $20 more than the Kreg Mini Jig but it comes with everything you need including a 3" square driver, some screws, pocket hole plugs as well as a case.

The Kreg Jr is a lot faster to use than the Kreg Mini because it comes with built in guides that can be adjusted for the thickness of material you're working with and the case includes a guide to help you adjust the stop collar on the drill bit.

One of the things that slowed me down a lot was having to stop and change the stop collar. In building my desk I used 3/4" and 1/2" plywood and I'd have to stop and readjust the collar using a tape measure. It was a very clumsy process.

With the Kreg mini I would have to unclamp, move the jig over, position it using the spacers, clamp it back down, drill and repeat. With the Kreg Jr I would have been able to just slide the jig over and not have to spend time realigning the jig. When you're making dozens of pocket holes, those few seconds saved each time really add up. A plastic insert allows you to attach the Kreg Face Clamp to the Kreg Jr Jig which makes repositioning the jig with one hand a snap.

Kreg K4 and K4 Master Pocket Hole Jig

The Kreg Jig K4 and Kreg K4MS Jig Master System are meant more for professionals and the serious DIY'er woodworker. The K4 runs around $100 and the K4MS goes for about $140. The Master System is essentially the same as the K4 with some extra useful accessories such as the face clamp, portable base, 6" square driver (in addition to the 3" driver) and a material support stop. If you're going to buy the K4 instead of the R3, might as well spend the extra $40 because those accessories come in handy.

The K4 and K4MS are more durable than the other systems. Because the drill guide is stationary and the work piece gets clamped to the dril guide you don't get a small point of pressure from the clamp on the plastic drill guide. My Kreg Mini has some dents in it from clamping with a standard C-clamp but is still usable.

If you frequently make pocket holes and have space on your workbench to permanently or temporarily affix the Kreg K4 Jig, you'll save yourself a lot of setup time. Just slide the work piece in the jig and clamp it down with one hand. A dust collection port allows you to hook up your shop vac to keep your work area clean.

Kreg Micro Pocket Hole Jig

The Kreg Jig Micro Drill Guide System makes 25% smaller diameter pocket holes and uses smaller pan head screws which allows you to make pocket holes in thinner stock.

If you frequently use 1/2" plywood or boards to make drawer boxes or picture frames, the Kreg Micro is for you. The Kreg Micro fits into the same bases and accessories that come with the K4 Master system and it can be used on it's own with spacers.

Even though the other Kreg Jigs can make pocket holes for 1/2" stock, many times 1/2" plywood comes in actual thicknesses of less than 1/2" and reducing the size of the pocket hole makes for sturdier construction in thinner pieces.

Kreg Jig HD Pocket Hole Jig

The Kreg Jig HD Starter Kit KJHD is specially designed for thicker stock such as 2x3's, 2x'4's and other 2x dimensional lumber. The holes are 25% bigger which provides up to 50% greater strength. This new Kreg Jig was first released in 2012.

Special screws were developed for the new jig that are larger and have a 3 special coatings to resist corrosion. This is a great jig for outdoor projects such as planter benches, outdoor furniture as well as indoor furniture made of dimensional lumber such as workbenches.

The Kreg HD drill guide can accept the Kreg Face Clamp and fits in the K3 and K4 jigs.

How To Make Square Cuts In Dimensional Lumber

It's important to get square cuts in wood when building certain projects. Square cuts allow you to create stronger joints and allows you to have your pieces fit together properly so that planter bench you're trying to build is straight and doesn't wobble.

There are a number of different ways that you can make square cuts in dimensional lumber such as 1x6's, 2x4, 2x6's, etc., which vary in price. Most will also allow you to make accurate angled cuts such as 45 degree cuts.

As with any tools, make sure to read, understand and follow all instructions that come with the tools.

Good

Speed Square and Circular Saw

The cheapest and quickest way to make square cuts in dimensional lumber if you already have a circular saw is to use a Swanson Speed Square as a saw guide.

Simply place the edge of the square on an edge perpendicular to the direction you'd like to cut and use the edge of the square as a guide to run the edge of your circular saw's fence on.

It's important to follow the guide carefully and to have a good circular saw that will sit flat on it's base and can be adjusted to a true 90 degrees.  I have a cheap circular saw that I bought for around $40 that was used for some demolition. I'm not sure if it ever sat flat or was able to get the blade square but it's difficult to get it to now.

If you're using this method do a test cut to make sure the cuts are coming out square. You can use the speed square to measure the angle of the cut.

Better

Miter Box

A miter box is a plastic box that has slits cut at precise angles that guide the saw to allow you to make fairly accurate angled cuts in molding or dimensional lumber. Years ago you could find affordable wooden miter boxes but these days all I see are the plastic ones like the Stanley 20-600 Clamping Miter Box pictured left which includes slits for a number of different angles, including face angles. It comes with a sharp back saw and cam pins to help hold your wood in place. The pins don't hold the wood that securely so some quick clamps would help.

Contractor Miter Box

The Stanley 20-800 Contractor Grade Clamping Mitre Box is similar to a Jorgensen miter saw I own. The Stanley has holes for cam pins but it's essentially the same. These are slightly more expensive than the yellow plastic miter boxes but are easier to mount on a work bench. The saw has a replaceable blade (click here for replacement blade) which makes it a little cheaper to own in the long run compared to buying an entire back saw. The hardened steel saw blade is also capable of cutting metal. If you need to make straight or angle cuts in metal, this is the best manual miter box to buy.

It may look like you can create almost any angle you'd like but it only will lock in on 5 detents for 90, 45 and 22.5 degreens (on either side). It is very affordable compared to power miter saws and provides accurate cuts. The saw blade is very sharp.

I find it easier to use some Quick-Clamps to hold the wood in place rather than the built in clamps.

If you like the idea of a manual miter saw that is safer, cleaner and quieter than a power miter saw but want something a little better you can have a look at the Nobex Proman Miter Saw.

Best

Power Miter Saw

A power miter saw like the Hitachi C10FCE2 10-Inch Compound Miter Saw is almost 4x as much as the contractor miter box but if you have a lot of square or angled cuts to make will be worth the price.

It's noisier than a manual miter box and sawdust gets everywhere but it cuts even hardwood in about a second and with little effort.  Compound miter saws are adjustable in 2 different directions and have more flexibility when it comes to angles. There are detents for the more popular angles but you can also usually lock them into any angle you'd like.

If you have a lot of cuts to make but don't want to spend over $100 you can look for a Factory-Reconditioned Ryobi ZRTS1141L 9 Amp 7-1/4-in Miter Saw with Laser or rent one for the day.