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

[MsCharlie]

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!

[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 · Accepted solution]

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!

[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!!