40mm Oak Worktop Butler Sink Cut Out

[leevis]

Hi All
Getting a 40mm Oak worktop delivered on Saturday and i will need to cut this down and install an opening for a 800mm butler sink.

I am going to get hold of a butler sink template but not too sure which bits to purchase for the router.

According to the spec, for the recess (which i am assuming is the butler sink opening) is a 12.7mm at least 50.8mm in length with a 30mm guide bush.

I am not too sure if i need a plunge cut one or a straight cut one.

As the worktop will be 40mm thick i dont know if i need to cut this in one go or do different depths, i am going to be using 1/2 inch bits but i guess i will need a few different depth bits?

My router has a guide bush of 30mm but i am not too sure if these just get put on the bits or whether the bits need to have these already? I have seen some with and some without.

The same thing will apply to the drip channel on the inside.

Another question though, the worktop needs to be trimmed to the right length. I am planning on using a jigsaw to get it in the ballpark and then cut with the router, would this be using the same bits?

 

[Deleted member 174758]

According to the spec, for the recess (which i am assuming is the butler sink opening) is a 12.7mm at least 50.8mm in length with a 30mm guide bush.

I am not too sure if i need a plunge cut one or a straight cut one.

As the worktop will be 40mm thick i dont know if i need to cut this in one go or do different depths, i am going to be using 1/2 inch bits but i guess i will need a few different depth bits?

You'll need a router with at least 1500 watts, preferably 2000 watts but it doesn't matter if it is a plunge router or not. It is, however, essential that you make the cut is several passes unless you want to risk cookkng your router or scorching the wood. What you should do with heavy cuts like this is to remove the majority of the waste with a circular saw and a hand saw or jigsaw first so that the router is only doing a trim cut of 2 to 3mm of material.

My router has a guide bush of 30mm but i am not too sure if these just get put on the bits or whether the bits need to have these already? I have seen some with and some without.

The guide bush goes onto the bottom of the router - the jig is designed to accommodate the 8.65mm offset that you get when using a 12.7mm cutter with it and a 30mm guide bush - this is the same offset that you get with UK-style kitchen joining jigs. For this type of cut, where the cut needs to be made in 2 to 3 passes what you don't want or need is a bearing guided cutter of any description

The same thing will apply to the drip channel on the inside.

What does the manufacturer specify for the drip groove? Personally I've always used a core box cutter of about 1/4 to 5/16in (6to 8mm) diameter:

but then I tend to make-up my own jigs for Belfast sinks, including the falling drain grooves (for which a core box bit is ideal)

Another question though, the worktop needs to be trimmed to the right length. I am planning on using a jigsaw to get it in the ballpark and then cut with the router, would this be using the same bits?

Yes, you need a 50mm straight cutter like yo do for the cut out, but just watch out with a jigsaw on such a heavy cut as the blades can bend in the cut - a circular saw is a far better bet as it won't bend or twist in cut and it will give you a perpendiucular edge. Also if using a jigsaw avoid downcut blades (T101BR) like the plague - they just can't cut straight in work on deep, heavy cuts like this. Try to leave yourself no more than about 6mm waste to route away - more than that (i.e. more than half the diameter of the router cutter) and you start risking a climb cut which can be dangerous

 

[opps]

I have only ever done a cut out for one once (for a friend). I jigsawed out all bar about 2cm. I purchased a long Trend router bit with a bearing at the bottom and allowed that to follow the profile of the sink. The sides of the sink tapered in slightly so I was left with a 6mm overhang- more than enough to hide the silicone seal.

The router bit was just under £80 and because the job was slightly outside of my comfort zone it took me half a day (including routing the rounded profile, and oiling the edges). My mate was happy with it. I must confess that there was a tiny breakout at the righthand side even though I tried to be careful to run the router backwards at that point. I superglued it back and then sanded it. No one else has ever noticed.

I was happy with the finish, and I am my biggest critic (bar my GF...).

 

[leevis]

OK i get it now, i have the guide bushes and they will fit into the jig (30mm and 16mm), with them on, i just do multiple passes of the worktop, gradually lowering the bit with each pass, 10mm per pass maybe?

Regarding the drip groove, there is no manufacturer instructions on it, its a 6mm wide groove which goes between the edge of the worktop and the sink on the underside to catch drips to stop them going under the worktop. No idea how deep it needs to be but i would guess something under 5mm? The rounded end bits look good but not sure if there is a 6mm version of these so a straight bit might have to be used.

 

[opps]

OK i get it now, i have the guide bushes and they will fit into the jig (30mm and 16mm), with them on, i just do multiple passes of the worktop, gradually lowering the bit with each pass, 10mm per pass maybe?

Sorry, I didn't realise that you have a jig. I wasn't paying attention. Out of interest, it is a universal jig or one that can be adjusted to suit the sink?

 

[leevis]

Its one that can be adjusted to the sink so should be relatively straightforward

 

[Deleted member 174758]

OK i get it now, i have the guide bushes and they will fit into the jig (30mm and 16mm), with them on, i just do multiple passes of the worktop, gradually lowering the bit with each pass, 10mm per pass maybe?

If you hog away the waste to 2 to 3mm off the line you should be able to do the cut in 2 passes

Regarding the drip groove, there is no manufacturer instructions on it, its a 6mm wide groove which goes between the edge of the worktop and the sink on the underside to catch drips to stop them going under the worktop. No idea how deep it needs to be but i would guess something under 5mm?The rounded end bits look good but not sure if there is a 6mm version of these so a straight bit might have to be used.

If you follow the link I gave you the cutter you'd need would be either a T404 (4.8mm diameter, 1/4in shank), a T406.5 (6.4mm diameter, 1/4in shank), or a T406.5 (6.4mm diameter, 1/2in shank) from Wealden (BTW NOT a random supplier, but a firm I highly recommend for both service and quality of product). The depth of cut should be approximately the same as the diameter. Drip grooves need to be set 10mm or so back from the edge, so with a 4.8mm diameter cutter and a 10mm set-back from the edge you will need to cut your worktop to have a 15mm or greater overhang. Drip grooves tend to work better if they have a radius bottom - there are no sharp corners to trap dirt or water and they are easier to clean out. I tend to make the cut out, sand the edges then flip the worktop over to do the drip groove. I don't know if your jig accommodates the drip groove or not, but a home-made template can be made by pinning temporary strips of something like 12mm plywood or MDF to the underside and running the router, with the guide bush fitted and the core box cutter installed against that temporary "fence". To get a 10mm set-back with a 16mm guide bush and a 4.8mm cutter you'd need the strips to be set about 20mm in from the cut edges. With a 30mm GB that would be about 27mm

Calculation:

Set back (S) = 10mm
Cutter diameter (D) = 4.8mm
Guide bush diameter = 16mm
Offset from edge of cutter to outside of guide bush (go) = 16 - 4.8 / 2 = 5.6mm
Distance from cut edge to template strip = S + D + go = 10 + 4.8 + 5.6 = 20.4mm

The cut needs to be made in a clockwise direction around the opening (to avoid climb cutting), pushing the router left against the template as you go. Don't worry about any pin holes you leave in the underside surface - they are on the underside and are unlikely to ever be noticed inside the cabinets

One thing I'd recommend is sealing the underside of the top around the sink cut out and back for 50mm or so from the cut edge with something more durable and waterproof than oil.