How do I secure MDF board so I can use a hole saw on it?

I have a flatpack shelving unit that I want to convert into a cat tower by cutting some cat-sized holes in some of the shelves and separator pieces (for my jerks to climb through/torment each other through). I have a hole saw attachment set from Bunnings, but I think I should clamp the pieces of board before I try to cut the holes, because otherwise the board will spin and I'll make a huge mess. I also probably want to clamp some scrap wood on the top so that the saw has bitten neatly into the hole by the time it gets to the MDF or whatever the shelves are made from.

I don't have a workbench or trestles or any clamps, and I'm not sure what to get - I think I need to clamp the board down onto a stable surface, including the scrap wood, and do I also need to clamp it from the sides so that there's no lateral movement? Do I need a workbench or a sawhorse or trestles, and do these have built-in clamps or do I need to get those separately, and what sort do I need?

One other question: how do I seal the edges of the holes so that the board doesn't give my cats splinters, or just shed woodchips all over the place - do I need to varnish it, or soak some wood glue into the exposed board, or should I get some laminate or plastic tubing or good old-fashioned gaffer tape?

I'm quite logical and good at working out basic DIY stuff, but this is a step up from my usual projects. Thanks in advance for your time and expertise!

Find more posts tagged with

Tools and Materials

Furniture

Building and Construction

Recycling and Upcycling

Accepted answers

GreenShoots

Hi @MsCharlie . You must have posted just as I was writing. I'm sure a small cat could get through a 127mm hole! You will want to make sure that you have your shelf firmly clamped to a sturdy and stable work surface so that it doesn't go spinning out of control when you put the hole saw to it. You will also want to wear eye protection.

I'm sure others here can offer more specific advice. I look forward to seeing the photos of your progress and the finished product!

All comments

Noyade

Good evening 😁 @MsCharlie

"I have a hole saw attachment set from Bunnings"

Dumb question (I only have a dog) - but what size hole would/could the average cat climb through?

What are the sizes in your set?

And what's the drill you'll be using? There is a tremendous amount of torque involved with large hole saws, as you've outlined above.

Looks like clamps will definitely be required.

Cheers!

MsCharlie

Cats are remarkable in their ability to squeeze through tiny spaces, and my cats are quite small examples of the species (both of them are around 4kg). The largest hole saw in the set is 127mm, which should be plenty big enough for them - if they're total drama queens about it, I can get a larger attachment from the Bunnings tool shop, and clamp some scrap wood over the board to engage the pilot drill and embiggen the holes. The recommended RPM for the 127mm hole saw is 250, and it's only going through whatever chipboard IKEA uses in their cheaper stuff, so I'm not expecting too much resistance. I'll take photos of the various steps, and the finished product (whether or not it's a success!) and keep you posted on how it goes. Fingers crossed. 👀

GreenShoots

Hi @MsCharlie . Like @Noyade I'm wondering how big a hole you have to saw for a cat to get through. I guess they can get through some pretty small spaces...

Have you seen this step-by-step guide How to build a cat tower? It sounds as though you want to do something quite different, but it might give you some inspiration.

GreenShoots

I'm sure others here can offer more specific advice. I look forward to seeing the photos of your progress and the finished product!

MsCharlie

Wow, what a great-looking cat tower! Thanks for linking me to that post. I have ADHD and a panic disorder, so I need projects that capitalise on my short bursts of motivation, which is why I'm repurposing this flat-pack shelving unit - most of the work is already done for me, and all I need to do is add the cat holes. Additionally, it means that the exterior of the shelves match the rest of my furniture, and the highest shelves can still be used for storage.

The shelving unit I'm using is the more expensive but identical IKEA version of the Bunnings one I've pictured here, and I'll be putting holes in the middle separators of the bottom two shelves, and the far corner of the first shelf, where I've added the red circles. The next shelf up (third storey) will not have any holes, and there will be blankets in there so that my older cat can hide and have naps free from harassment from her little brother. At this point, my plan is to staplegun one of the fabric/cardboard box inserts into one side of that storey, but on its side so that the front is open but the back is protected from stealth attacks. If little brother finds a way to menace big sister through that, I'll upgrade it to a wooden backing.

The top storey will have drawer inserts in it so that we can store the millions of cat toys and treats and spare collars and worming paste etc. in there.

If I get more motivation once all of this is done, I have some leftover carpet offcuts which I'm thinking about attaching to the side and top of the unit, so the jerks can climb up it like a tree (we live in an apartment, so they don't get to play in real trees), but that's a project for Future MsCharlie!

MsCharlie

Might head down to Bunnings and see what they have by way of a folding workbench and some clamps. Thanks so much for your advice!

TedBear

A tip for getting clean cuts with a holesaw, only allow the saw to go halfway through the board. Then turn it over and using the hole that the drill bit makes, which will have fine right through, you can finish the hole off from this other side. That way you don't get a rough edge from the saw teeth breaking through the far side, as you would if you just saw directly through from one side to the other.

MitchellMc

Welcome to the Bunnings Workshop community @MsCharlie. It's brilliant to have you join us and wonderful to see our helpful members have been assisting.

You won't need any special workbenches to drill these holes, just a solid surface to which you can clamp. However, I'm sure a small clamping workbench would come in handy for any future projects. If you have a stable table or bench with an overhanging edge, you can use a towel to protect it and then clamp your board to it with two IRWIN QUICK-GRIP 300mm Medium Duty Bar Clamps. These are fantastic clamps that will serve you well for many years to come. Alternatively, you could use some more budget-friendly G-clamps. I've created the below rendering to illustrate how to clamp the board.

I recommend applying a few coats of White Knight 100ml White Gloss Splashes Enamel Paint for the exposed chipboard edges. That should seal the surface and match the colour.

On a side note, thanks for bringing the word embiggen to my attention. I actually had to look that up. First recorded use in 1884 and repopularised in '96 by its use in The Simpsons. Interesting!

Keep us updated on your project, and reach out if you need further assistance. Also, once finished, please post photos of your kitties playing in their new cat tower.

Mitchell

MsCharlie

This is a crucial tip!! Thank you so much. The other important side effect of this tactic is that the piece of board will (hopefully) not be stuck all the way inside the holesaw, making it nearly impossible to dislodge. We did a shallow cut on one side and then flipped it over to do the bulk of the cut, and then spent about half an hour wrangling the cut piece out of the holesaw, which was enough time for it to start raining, so we've packed up and will do the other pieces tomorrow, making sure we go properly halfway through on the first side this time!!

MsCharlie

Thanks so much for your detailed response, Mitchell. That diagramme is especially helpful, and much better than the one I provided above!

We ended up using an adjustable workbench (pictured), with moveable 'dogs' to clamp the board from the sides, although we did end up needing one of us to put weight on the far end of the board to hold it down because of the amount of pressure we had to exert to get the holesaw fully through the board - we will definitely use clamps to vertically secure the remaining pieces!

With regard to the enamel paint, it turns out that the shelving is made from chipboard (not MDF), which will apparently expand and fall apart if we use a water-based enamel paint. Do you by any chance have some updated recommendations for sealing the exposed edges, now that you have the correct information? (Sorry for not realising that chipboard and MDF aren't the same thing!)

I'm glad to have introduced you to such a useful and cromulent word - I don't know how we ever got by without being able to embiggen things! Thank goodness for Jebediah Springfield. 😀

MsCharlie

Okay, so the update is that our very good quality cordless AEG drill got a very hot motor and then started emitting smoke after getting maybe a third of the way through the chipboard. We switched to the cordless AEG hammer drill (pictured) which did NOT catch on fire, but still needed a *huge* amount of pressure to get all the way through - because we were only using an adjustable workbench with 'dogs' to clamp the board from the sides, we ended up needing one of us putting weight on the other end to hold it down.

It then started raining in the 30-odd minutes it took for us to wrangle the cut piece out of the holesaw, so we're going to resume the project tomorrow, using my stepdad's big fancy saw table and as many clamps as we can fit on there!! We'll also use the tip provided by TedBear below, cutting halfway through the chipboard from one side and then the other half from the other side, in the hope of the cutout not getting as firmly lodged inside the holesaw. I'll keep you all posted!

Noyade

Very nicely done! @MsCharlie

Is that the big hole-saw seen in the background of your first photo above?

Any trouble getting it off the drill component afterwards?

I have found this 'pin' attachment really good with hole-saws.

EricL

Hello @MsCharlie

Thank you very much for the update on your cat tower project. It's good to see that you're making progress, just a friendly reminder that if your drill has a setting for drilling to set it to that function. Another way to seal the chipboard is to use an oil-based primer, it will be safe to use as it will not make it swell like water-based paints. Thank goodness for Jebediah Springfield!

Eric

MsCharlie

Ah, the famous Eric L of DIY Cat Tower renown! I'm honoured to make your acquaintance. 🙂

Updated update is that we bought a 152mm Sutton multipurpose holesaw that fits on the mandrill my stepdad already owned, and we've moved the project to his vertical drill press because using a hand drill is harder to control the RPM, whereas the drill press has a belt system to set exactly what speed is recommended for each job (the larger holesaws want 250 RPM, because of the torque). The drill press also guarantees even pressure from exactly above, so the hole won't be angled - this is especially useful when removing the cutout from the attachment, because if you cut even slightly wonky, the cutout piece will be wider than the holesaw attachment and REALLY jam itself in there!

I'm not super happy with the result from the multipurpose attachment, as it only has three quite fat cutting edges and has basically torn up the edges of the melamine - you can see the difference between the results in the images - the pile of holes is from the Sutton multipurpose attachment, and the other one is from the cheap brand. If I do this project again (I've already had requests from a bunch of my friends and family members!) I will get the Sutton attachment that says it's for metal, because it has lots and lots of little teeth, and I think that will cause the edges to be neater?

The sketchiness of the edges means that I will have to sand them (using fine paper wrapped around some dowel) and fill them with putty (packing it in and smoothing it with the dowel so I can kinda roll it and get a nice round finish) to make sure that the laminate doesn't peel off any further. I don't think a primer will do the job with the edges as ragged as they are this time around, but it sounds like a good option for future attempts with the other holesaw attachment - thanks for the tip!

MitchellMc

Thanks for the updated update, @MsCharlie. You'd be correct in thinking that more teeth typically mean neater holes. You're also right that some timber filler and sanding will smooth out those edges; you'll then be able to prime and paint over the filler and inside of your cutouts.

I can't wait to see this finished!

Mitchell

MsCharlie

Long-awaited update!

After filling the edges with putty and then sanding them, applying two coats of primer (sanding between), and several coats of high-gloss paint (lightly sanding with a very fine sandpaper between coats), the holes have been deemed acceptable for our fluffy tyrants to use as throughways. I've attached some photos for approval!

My partner and I both have ADHD, so we start a lot of projects at once, and we're only now assembling the shelves. Would it be useful for me to write up the whole project in a single entry and post it as a separate piece? I'm new here, and I don't know how helpful that would be.

Anyway, I'll post pics when we've assembled the shelves and the cats are steadfastly ignoring them, as is traditional!

MsCharlie

Updated update, the shelves are now assembled. Thank you to everyone for your help, one of the jerks is already having a great time investigating!

Jason

Feel free to write up the project as a seperate piece @MsCharlie. I'm sure the community will be inspired by what you have created for your furry friends.

Thanks for sharing.

Jason

Noyade

Looks great! - and don't those cats love it. Very clever. 👍

Child Item