wooden worktop with undermount sink

[trevw]

Hi,

I've had a search through the posts for tips on cutting the hole for an undermounted stainless steel sink in a 40mm walnut worktop.. none seem to quite fit. The closest seem to advise drilling holes for the corners and either jigsawing the corners then handsawing the straights or just using a jigsaw for it all.. (if I did that would I cut it slightly small and sand the last couple of mil?)

I've also seen talk of routers/jigs, but not sure how this would work/where I could get them/if it gives a better finish?

I have seperate sink templates (there is also an undermounted stainless drainer) any recommendations on a suitable gap between the two to retain enough strength in the top?

also, the instructions advise a bead of silicon to seal the sink to the underside of the worktop, however I was planning to seal the wood with oil a few times top and bottom + edges so presumeably this would struggle to stick?

any thought appreciated

many thanks

Trev

 

[Scrit]

Hi Trev

I'd forget about using a jigsaw alone because the blade will inevitably wander leaving you with a huge amount of clean-up to do. Not nice, or easy! The jigsaw is useful for doing the initial cutting away of waste, but the finish cut is done using a 1/2in plunge router (1800 watts or so), with either a guide bush and straight cutter or a bearing guided bit. That minimises the clean-up required. Don't try to do the entire cut with the router alone because you'll probably end up with scorching problems, especially if you're not an experienced router user and the amount of dust generated by the process will become a real headache

I've also seen talk of routers/jigs, but not sure how this would work/where I could get them/if it gives a better finish?

As far as I'm aware there's no such thing as an off the peg jig for a Belfast or undermount cut-out unless the sink manufacturer happens to do one. What they probably supply is a cardboard or paper pattern which needs to be transferred onto a piece of void free (birch) plywood or dense MDF, sawed out with a jigsaw and then sanded smooth. I'd suggest somethinhg like 15 to 18mm thick material for this. I'd also suggest using the largest diameter top bearing guided template cutter you can find, run at a reduced speed because smaller diameter cutters seem to be a lot "jumpier" and require more clean-up. I tend to use a 25 to 30mm depth cutter for the first 30mm of worktop taking no more than 10mm extra depth per pass and then a longer cutter for the finishing cuts at 5 to 6mm extra depth per pass. The first couple of cuts are made using the template which is then removed and opening itself then becomes the template for the guide bearing to follow. A good source of cutters is the Wealden Tool Co.

You can make up a template guide to work with a straight cutter, but you'll need to use something like 10 to 12mm thick material to accommodate the length of the guide bush remember to make the jig bigger by the amount of the cutter/guide bush offset, e.g:

Cutter diameter = 12.7mm (standard worktop cutter, 50mm long)
Guide bush diameter = 30mm (standard worktop size)

Offset = (GB diam - Cutter diam) / 2 = 30 - 12.7 / 2 = 8.75mm

You'll also need a 50 to 60mm long cutter to do the job and preferably again in small passes. This way is cheaper, but making the jig is more fiddly and time consuming, I find

I have seperate sink templates (there is also an undermounted stainless drainer) any recommendations on a suitable gap between the two to retain enough strength in the top?

70 to 100mm

... the instructions advise a bead of silicon to seal the sink to the underside of the worktop, however I was planning to seal the wood with oil a few times top and bottom + edges so presumeably this would struggle to stick?

No. If you don't use a bead of silicone you'll be forever flooding the cupboards below your sink/drainer

Scrit

 

[trevw]

so, just to check I've got it right, something like this?
http://www.screwfix.com/app/sfd/cat/pro.jsp?id=95675&ts=69075

then either the top bearing (e.g. from http://www.wealdentool.com/acatalog/Online_Catalogue_Template_Trim_279.html)

or just using the guide bearing with an enlarged version of the template and straight cutters .. maybe from a kit, like this? http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=A338072&ts=69677&id=21039#

by the way, any tips on butt joints along a run (run is 5.6m with sink in center) and a corner joint for the same 40mm walnut top?

thanks

Trev

 

[Scrit]

Yes. Personally I use the bearing guided bits.

by the way, any tips on butt joints along a run (run is 5.6m with sink in center) and a corner joint for the same 40mm walnut top?

Make the joint as straight as you can, level using a few biscuits (see 4mm slot cutters - Lamello acytually make plastic non-glue biscuits for just this purpose) and pull the joint together using three standard kitchen worktop connectors (you'll need to make a jig for their mushroom housings, too, or buy one, or hire one for the day). Make sure you've sealed the ends before joining and add a bit of clear silicone to the joint. Finally, take any minor level discrepancies out with a sharp hand plane or possibly a belt sander.

Scrit