Cutting laminate worktop

I am replacing a single length of worktop.
I need to make a cut out for a sink in the new 28mm chipboard laminate. I *think* I'm going to be using a Bosch 101B jigsaw blade. That's marketed as a 'clean cut' blade.
I'm wondering whether I should work from the good side of the laminate, or should I turn the worktop over and run the jigsaw from the underside of the worktop? The 101B blade cuts on the upstroke.
I also need to shorten the worktop a bit, and I'd like to use the circular saw for that. Is that going to make a mess of the laminate? Again, which side of the worktop should I work from? The cut edge will be hidden by a bead of silicon, but I don't want to have to use a huge bead just to cover the chips.
I know that the right way to do this is to cut it over-length and finish off with a router, but I'm trying to keep this job as simple as possible. I have already packed a boot full of tools for this one small job. Am I going to regret not using the router?
Finally, I'm going to be reusing the old sink. Can I just silicone that in, using whatever rubber seal is still there, or do I need a special mastic?
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On 13/08/2019 20:18, GB wrote:

I've always cut 'face down' (so the teeth cut into the good face).
When cutting to length, make a 'fence' to guide the saw and keep it straight. I find this makes a huge difference when it comes to reducing chipping. You can get a good finish with a saw. Those perfect mitre joints are another matter ;-)

For sink seal, I'd be tempted to try and find some of the sealant on a roll. I've used this before, It is about 1cm wide, a few mm thick, and a bit like silicone on a roll. It will stick to the sink if you remove the old stuff and deform to make a new seal when you do the clamps up.
Otherwise, silicone is fine, just more of a faff.
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The term "clean cut blade" is a term used to describe a blade that unlike a standard blade will produce a clean cut on the top surface. I would try it on some scrap material first you may end up getting chipping on the surfac e you want to keep clean. With jigsaws the quality of cut does seem to depe nd on the quality of the jigsaw itself.
Richard
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On 13/08/2019 21:44, Tricky Dicky wrote:

+1
With a sink cut-out and with a stainless sink with integral draining board minor chipping can always be covered with the sink.
Always seal the cut edge of the hole - spread some silicone sealant on the cut edges.
I've used old sinks on new work surfaces by first cleaning of any old sealant then running anew bead of silicone sealant around the edge of the sink before inverting it and placing it in the cut-out hole and clamping it. Clean off and excess sealant with a Fugenboy[1]
[1]
https://www.youtube.com/watch?v=jgcqi5LoLSI

Other brands with similar names are available - often cheaper with more pieces. Aldi/Lidl often do 5 piece kits for a few quid.
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On Tuesday, 13 August 2019 20:18:23 UTC+1, GB wrote:

The blade needs to push the laminate into the bulk when cutting, not away from it or it'll chip badly. Jigsaw blades can easily bend all over the place, making caution required when cutting from the underside.
NT
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The sink usually has a wide enough edge strip to cover any chips. I would cut from the top.
Seal the cut edge and any chips with waterproof wood glue: soaks into the chipboard, and leaves a thick waterproof film. This keeps the chipboard from swelling should water find its way through; otherwise, it swells, letting more water through, and fails quickly.

Probably best to cut from the underside, but that depends on the blade. Some will give a near-perfect cut on top.
So use the sink hole offcut for a test cut?
And I saw an experienced pro clean up a routed edge he was unhappy with by using a hand plane... (yes, the result really was an improvement).

I'd use silicone. The one special mastic strip I used oozed traces out, as it was permanently elastic, and dirt stuck to that ooze. Comes off easily with WD-40, but it is annoying.
Thomas Prufer
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I recently used my relatively elderly Bosch jigsaw fitted with a brand-new (Bosch) fine-tooth blade to cut the sink aperture in a new worktop. Working from the top surface gave me a very clean cut.
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You can get blades which cut downwards. Are they better for this job or not? You certainly need a very firm hand on the saw.
--

Roger Hayter

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On Wed, 14 Aug 2019 08:56:53 +0100, Roger Hayter wrote:

ISTR Makita doing a blade that cuts upwards except for the very top bit that cuts downwards Seemed like an ideal tool - I was tempted but never had a use for it :-( Well, there's this: https://www.makitauk.com/product/b-10970.html and this: https://www.makitauk.com/product/a-85793.html
--
Peter.
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On Wednesday, August 14, 2019 at 9:26:42 AM UTC+1, PeterC wrote:

and very important turn off any pendulum action your jigsaw may have
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On Wed, 14 Aug 2019 03:26:09 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

Yes! - I'd forgotten that.
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Peter.
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On 14/08/2019 08:56, Roger Hayter wrote:

I also seem to remember that turning off the orbital action of the jig saw was recommended for laminate cutting.
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On 13/08/2019 20:18, GB wrote:

As long as you use a decent blade any minor chips will be covered by the lip of the sink. Masking tape helps in 2 ways, easier to see cut line & helps prevent chipping.

Cut from the back starting at the rounded edge. Use a saw board or guide and make sure the cut is supported both sides.

Not necessary.

I've always used silicone.
--
Dave
The Medway Handyman
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On 14/08/2019 15:22, TMH wrote:

Can I thank everyone for the input. The job went very well.
We inverted the worktop and cut it to length with the circular saw. That gave a reasonably clean cut.
We turned the worktop right way up, taped where we wanted to cut, and used the ancient B&D jigsaw. The only thing I would do differently is that I'd cut the hole slightly oversize to begin with. It saves about 15 minutes shaving bits off the hole afterwards!
Whilst waiting for the sealer round the hole to dry, we prized off the mastic from the old sink (another 15 minutes job) and ran a generous bead of silicone round. We also made a hole in the sink for the tap. (The Ikea Fixa tool works a treat and is not expensive.)
Then, working from underneath, we put enough of the old clamps back to hold the sink in place. Then turned it over yet again to fit the rest of the clamps and the tap.
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On 15/08/2019 11:41, GB wrote:

Really helpful to get a feedback report on how the job went. Wish more people would do this.
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