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I have a bookshelf with a plywood back, the plywood is 3mm thick. The bookshelf is against a power point so I want to out a rectangle to allow the power cords to get access to the power point when needed.

How is the best way to cut it out? What tool should I use?

Edit* The rectangle does not need to have sharp corners. It just needs to be clean looking and provide access to powerpoints

user1605665
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    One way is to drill a hole, then use a jigsaw to cut out the opening you want, starting at the hole. You could also use a router to cut out the opening from the hole. – Armand May 23 '22 at 23:30
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    What tools do you have? Can you move the bookshelf out or do you have to work on it in place? – manassehkatz-Moving 2 Codidact May 23 '22 at 23:31
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    On many shelves in the last 20 years or so (especially the type you buy in a package and assemble yourself at home) will have a cheap paperboard back that has a printed surface to look like wood. – Michael Karas May 23 '22 at 23:44
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    If the back is actually cardboard, as noted by @MichaelKaras, then a simple utility knife is all that's needed. As you can see in the answers you have so far, the proper tool depends on whether the book shelf has been installed already or if you're still in the planning stages. It would help if you would [edit] your question to indicate whether it's currently full of books or not. – FreeMan May 24 '22 at 12:18
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    @MichaelKaras it's more likely to be hardboard (Masonite) which cuts nicely with a jigsaw (from the back). The veneer is even occasionally real wood – Chris H May 24 '22 at 12:18
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    Assuming the back is actually plywood (or at least MDF), and not paperboard... why do you need a rectangular hole? From your description of the actual problem — wanting access to a power "point" (outlet?), I would think a suitably sized round or "slot" (two halves of a circle "pulled apart" such that the ends are connected with straight, tangent lines) hole would suffice... which you could easily cut with a hole saw (and jigsaw, in the "slot" case). BTW, you'll want a sacrificial piece of wood held firmly to the back to minimize edge fraying when you make the cut. – Matthew May 24 '22 at 20:25
  • If the hole is just for power cords, then a hole saw will make a round hole large enough. – Pete Kirkham May 24 '22 at 20:51
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    Once again, location is important for good answers. The hole size for UK plugs will be substantially larger than that of, say, Continentals, which could get away with a round hole (hole-saw), which won't do such a good job in UK. – Tim May 25 '22 at 08:26
  • And a round hole might not work at all in the US, @Tim, where cover plates are rectangular and the mounting screws need to be accessible without moving furniture. I support your request for a locale. – FreeMan May 25 '22 at 14:04
  • @FreeMan - in the past, I've even re-mounted the socket onto the backboard, on the understanding the bookcase doesn't get moved without me knowing first ! Much tidier job, maybe contravenes present-day regs... – Tim May 25 '22 at 14:09
  • Not NEC legal, @Tim. It puts combustible material (plywood, cardboard, whatever) inside the confines of the box which is supposed to protect combustible materials from sparks/arcing that might happen inside the box. – FreeMan May 25 '22 at 14:17
  • @Tim (I'm in the UK) I cut out a hole sized to match the whole socket faceplate, to be more sure of fitting chargers/power supplies etc., and of course out mains leads come our of the plug downwards. Not sure about UK regs on that, but seems like a recipe of a problem if someone try to move the furniture and rips into the electrics - different for truly built-in – Chris H May 25 '22 at 14:17
  • Do you really want a rectangle (sharp corners), or is a rectangle-ish (rectangle with rounded corners) adequate? – user3067860 May 26 '22 at 14:20

4 Answers4

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I've often done this using a jigsaw, with the bookcase face down, or before assembling it. I assumed you want sharp corners - jigsaws can cut fairly tight turns but not sharp. I wouldn't run the saw along a fence for this, though you could.

  • Mark out the cutout on the back
  • Drill a hole bigger than the blade (10mm or 3/8" works well) near but not at one edge.
  • Saw, forming a smooth curve to meet the side, ending at a corner (maybe turn a bit sharper than I've drawn, but it's not to scale.
  • Take out and reverse the saw to finish that side
  • To cut the other sides, back the saw away from the corner, and make the turn onto the new side.
  • Again, cut into the corner by turning the saw round.

You may need to sand a little where the cuts from opposite directions meet, but with practice that shouldn't be needed.

cutting out a rectangle with a jigsaw

Jigsaws give the nicest finish if you work from the back, because they cut on the pull stroke so any tearing out is on the face you're working from. The sole blade can also leave marks.

Here's one I did with a jigsaw, to fit a UK double socket (but I've since moved the bookcase to another place).

cutout in ikea billy bookcase

That's Ikea Billy, so a reasonable particleboard with a fake wood veneer.

Chris H
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  • Well described, and exactly what I would do. – FreeMan May 24 '22 at 12:16
  • To the user who suggested an edit about cutdown blades - it wasn't clear, but if you explain in a comment I'll try to incorporate it. Those I've seen won't help with tear-out as you seem to suggest, but might help with working in a confined space - indeed, metal-cutting blades work fine in thin board if used gently and are shorter than wood blades – Chris H May 25 '22 at 10:08
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    Depending on the material the back is made from, one possible finishing touch would be to cover the edges with black tape (electrical or gaffer's tape would work, but needs to be wide enough to go around without peeling off). This can help cover any slop if you're not super-skilled with a jigsaw. The trick is to wrap the tape so that most of it is on the back and you have a nice, even line on the front, say 1 cm wide (or 1/2" depending on your choice of units). Works best if the original material is already a dark color on the front, but when cut you can see the lighter edges inside. – Darrel Hoffman May 25 '22 at 13:27
  • I've done basically the same thing except using a drill bit on a Dremel using a shield that sets the depth of the cut. I trace the line with a pencil and then poke in the corner and trace around. I've got this one: https://smile.amazon.com/gp/product/B0000302YS/ – StalePhish May 25 '22 at 14:55
  • @StalePhish I've never really like those rotary cutting bits for straight lines, unless running against a fence. They're too willing to curve. But I haven't had one that you can hold as nicely as the one you linked – Chris H May 25 '22 at 14:58
  • @ChrisH I've only used it for cutting through drywall for new electrical outlets and not on wood, in which case it doesn't need to be perfect because any jagged edge should be completely covered by the switch plate. For going through wood, maybe even a circular hole with a rubber gasket around the edge would be fine, as long as it's bit enough for the end of the cord to fit through (we've all had trouble putting a monitor cable through the slot on the back of a monitor stand) – StalePhish May 26 '22 at 14:22
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The almost optimum tool for cutting a hole like this is the oscillating type saw. You can get these into a fairly tight spot and with control of the tool you can avoid damage to the wall or power point sitting behind the shelving unit. Other solutions such as a jig saw can cause damage behind the shelf unit unless you move it away from the wall before cutting.

Michael Karas
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A recently developed tool for oscillating drivers is this tool. I know product recommendations are off topic here, but I couldn't resist passing this info along. It's intended for sheetrock, but would probably work OK with 3mm plywood.

box cutting tool

George Anderson
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    At that price, you'd have to use it for more than just a one-time bookcase fix to make it worthwhile. – manassehkatz-Moving 2 Codidact May 24 '22 at 03:04
  • $72 so you can cut four sides at once? You can buy the whole oscillating saw tool for less than half of that. https://www.harborfreight.com/2-amp-variable-speed-oscillating-multi-tool-57808.html?_br_psugg_q=oscillating+multi+tool – gnicko May 24 '22 at 03:05
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    @gnicko Harbor Freight is Chinese crap. The most expensive tool you'll buy are cheap ones that you'll have to replace 5 times. The OP can make his/own decision as to whether this is an appropriate tool for him and the future. Don't dis on me just BC I suggested what I think is a way cool tool that could help a newbie do a good job. – George Anderson May 24 '22 at 04:13
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    Could be a cheaper option for some who might do a lot of damage with other tools suggested :) – Solar Mike May 24 '22 at 09:36
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    @GeorgeAnderson some HF is Chinese crap. Some is actually pretty decent. Granted, my standard is to not buy power tools there, but I've purchased hand tools from them, had a couple break, and simply walk in with the broken one, pick up a replacement from the shelf and after 3 minutes of fumbling at the check out register, I have a functional replacement, free of charge. Their quality is getting better. Also, if you know what you're getting into when you buy there, then a 2nd use of the one-off tool is a bonus! </OT product/store recommendations> – FreeMan May 24 '22 at 12:14
  • C'mon @GeorgeAnderson.... – gnicko May 24 '22 at 15:33
  • @FreeMan I've seen lots of your posts and I think we agree on most everything. HF, while I go there once in a while to buy "disposable" tools, it's not a regular spot for me. Maybe I'm prejudiced bc a number of years ago, they got hacked. I'd used a debit card there, got a letter in the mail saying they were hacked. I checked my bank account and sure enough, they got me. Apparently I had a "VERY GOOD TIME" in India to the tune of about $2,100 (liquor stores, houses of "ill repute", etc) and no I wasn't in India. Bank got the money back, but it took months. – George Anderson May 24 '22 at 15:37
  • @GeorgeAnderson, I get your problem with HF, but pretty much every hardware chain and other large distributor has been hacked at some point. HF is great for people who might use a tool once or use it 2-3 times a year, definitely not for pros. You have to understand why you are buying something before you consider how much to pay or what quality you are needing. For example, not everyone needs a $2400 nailgun like a framer or roofer might. https://www.homedepot.com/p/Hilti-22-Volt-Lithium-Ion-Cordless-Bluetooth-Nailer-with-Fastener-Guide-2194599/313650005 – computercarguy May 24 '22 at 18:31
  • @computercarguy No arguments there. But there's not much worse than having a cheap ass tool crap out on you in the middle of a job. It may have a warranty, but you still have to take your time to go to the store, which might be quite a ways away, and hopefully they will honor the warranty and have a replacement unit in stock. When it comes to needing a high end, reliable tool for one off project, I usually turn to the rental market. BTW, are there really nailers that cost $2,400?!?! – George Anderson May 24 '22 at 21:48
  • @GeorgeAnderson, that goes for any tool warranty and store. I've had "good" tools that broke in the middle of a project and the store was distant and either didn't have a replacement or didn't want to honor the warranty. I also had a Mac ratcheting wrench that broke, but because I'm not a mechanic, it took years before I stumbled on a Mac truck to get it fixed. Evidently there's one nailer that's nearly that price. I looked around, but couldn't find another one that was even $1000. – computercarguy May 24 '22 at 22:11
  • It's kind of amazing that this product exists. It's so insanely specialized. – Christopher Schultz Jun 01 '22 at 20:20
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Best would probably be a router. Using a template to be sure the hole is nice and neat. You can get less expensive small routers (for most intents and purposes) as "laminate trimmers" and "cutout tools" - heck, you can get a router base for a Dremel (-type) tool and that would be adequate for this little job.

There are many other ways to get there.

Ecnerwal
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  • Unfortunately, making an accurate template for the router is a skill in and of itself. I've made one or two and don't have enough practice yet to make them well. Maybe there's a trick that I need to learn... – FreeMan May 24 '22 at 12:11
  • For something like this, it's trivial. Plain old rectangle. Measure from the edge of the router baseplate to the closest side of the bit. Attach 4 boards to the workpiece that far from where you want the edge of the hole, typically with double-stick tape. [Can do the same thing with less offset using router collars, or no offset using a bearing guided bit.] Run the side of the router baseplate against the edge of the boards, and like magic you have a nice clean hole with rounded corners (the radius of the router bit.) – Ecnerwal May 24 '22 at 12:20
  • Hard to get a tight, right-angle corner with a router... – MikeB May 25 '22 at 15:13
  • ...And why would you need or want one for an access hole? But if you do, a minute or two with a file would do the trick on 1/8" plywood. – Ecnerwal May 25 '22 at 15:15
  • Given the nature of the question, it's clear the asker doesn't have a whole workshop full of tools. Almost everyone has a drill, much less likely to have a jig saw. Almost nobody has a router, so while this answer may be accurate, it's not very helpful IMO. – Christopher Schultz Jun 01 '22 at 20:18
  • Given the nature of the question, it would appear that the questioner is considering tool purchase. A small router (aka laminate trimmer) is quite affordable, and that, on a small scale, or a larger router on a larger scale, plus a few simple jigs can do jobs that are normally thought to require huge expensive tools that take up more space as well as costing more. They have also now clarified that sharp corners are not required. But you are welcome to your opinion. – Ecnerwal Jun 01 '22 at 20:31
  • Fair enough. I'll delete my comment as it's not constructive. I wasn't going to downvote the answer, BTW. – Christopher Schultz Jun 02 '22 at 16:23
  • No worries. I did freely acknowledge that there are many other ways to get there, but for me, for a truly nice clean hole, the router wins. 1/8" ply, you could cut it out with a utility knife and perseverance, perhaps even make it look good if using a straightedge. – Ecnerwal Jun 02 '22 at 16:50