Routing for an Inset induction hob

[mal165]

Hi, im quite experienced at woodworking, less so with routing. I woukd really appreciate advice on how to proceed with this little task. I want to flush fit an induction hob into a worksurface.
The MI show a 6mm radius at the corners and requires a rebate of 17 x 5 on top and bottom edges and 19 x 5 on remaining edges. These dimension are critical. The hob body cut out will be 580 x 499
Thanks in anticipation.

 

[ChaiLatte]

Make a rectangular template out of 12mm MDF that fits snug around the "expanded outside" of the hob. The hole is 2mm each side larger than the hob itself, so use 2mm Broadfix packers (white) between hob and template to obtain the correct size. The finished internal dimensions of the template need to be 599 x 524mm. Make the template hit and miss at the corners and you don't need to measure anything, just make sure the side touching the hob packer is straight and the template has one side square to its face.

Use a top bearing guided bit registering off the template. Use an offcut of MDF on the inside of the cut to stabilise the router base. Once the outside of the groove is formed, use a shim (16mm wide, cut from the same 12mm MDF) on the inside of the template (insert the shim so the 16mm dimension is upright. It will drop into the 5mm deep groove already formed but will not stick above the top of the 12mm template) and run round it again to ensure the 5mm deep groove is minimum 19mm wide.

Cut out the middle after the groove is formed. You could again shim the original template to establish the edges of the cut (but unlike above, that requires you to cut exact width, parallel-edged shims [2 x 17mm; 2 x 19mm]. For the full-depth cut, a small error here will not matter).

The challenge will be to find a 12mm bearing guided bit but with the 2mm clearance a 1/2" one (12.7mm diameter, 6.35mm radius instead of the specified 6mm), which is far more plentiful, will be OK.

Do a test run in the offcut of the MDF sheet first.

The way the rebates are dimensioned is misleading. It is the largest dimensions of the entire hole that are critical. The 17mm and 19mm just say how far from the outer edge the full depth cut needs to be.

 

[Phill05]

What I have always done is cut a template out to the size of the hole you will need less the width of your cutter, double sided tape to place where it will be or drill screw to worktop, if you have a fence setup to your router use it to go around the template to form the rebate adjusting fence to suit width of rebate, this way you don't need bearing guided cutters just to do one job.
Finally move cutter back to edge of template cut down into worktop make hole for hob.

 

[imageel]

I did one of those a few years ago, a flush fitting 750 x 495 Miele hob into an Ikea solid oak block worktop and one problem I found was that most router cutters are negative rake - so cut on the up-stroke and in these worktops that created an edge 'feather' of hard to remove wood fibres -as in hard to remove without rounding over the edge!
I ended up - will admit after trashing one 2500m piece as I neared the end of the cut the cutter touched the end and danced over the worktop surface before I could turn it off, of buying a solid carbide positive rake Trend cutter that did a proper job..
It was my own kitchen so took the loss on the chin and was only used edge guides so no template and doing the small corner radii by hand....

 

[mal165]

Many thanks for the advice and hints. I reckon I'll need to give this some serious thought. I was actually thinking of getting a template laser cut to give me the accuracy and piece of mind. Certainly a dummrun ( or two is a must. I like the simplicity of using a fence but would need to include stops at the corners to prevent the router travelling too far. Any thoughts on pros and cons of using guide bushes for this job?
Thanks again

 

[MorrisWoodman12]

I would certainly use a larger template where you rout on the inside. That way if you don't keep the guided router bit tight enough to the template then the 'error' is into the waste material rather than wrecking your worktop.
Have fun
Martin

 

[HOJ]

Would something like this work, I made a similar arrangement in past out of MDF strips, mind you I cant remember why, but it must have worked! : Jig

**I remembered, I made a batch of shaker style door out of 22mm slabs of MDF and routed a V groove in them to mimic the stiles and rails

 

[mal165]

I would certainly use a larger template where you rout on the inside. That way if you don't keep the guided router bit tight enough to the template then the 'error' is into the waste material rather than wrecking your worktop.
Have fun
Martin

Good point Martin, thanks

 

[mal165]

Would something like this work, I made a similar arrangement in past out of MDF strips, mind you I cant remember why, but it must have worked! : Jig

**I remembered, I made a batch of shaker style door out of 22mm slabs of MDF and routed a V groove in them to mimic the stiles and rails

Make a rectangular template out of 12mm MDF that fits snug around the "expanded outside" of the hob. The hole is 2mm each side larger than the hob itself, so use 2mm Broadfix packers (white) between hob and template to obtain the correct size. The finished internal dimensions of the template need to be 599 x 524mm. Make the template hit and miss at the corners and you don't need to measure anything, just make sure the side touching the hob packer is straight and the template has one side square to its face.

Use a top bearing guided bit registering off the template. Use an offcut of MDF on the inside of the cut to stabilise the router base. Once the outside of the groove is formed, use a shim (16mm wide, cut from the same 12mm MDF) on the inside of the template (insert the shim so the 16mm dimension is upright. It will drop into the 5mm deep groove already formed but will not stick above the top of the 12mm template) and run round it again to ensure the 5mm deep groove is minimum 19mm wide.

Cut out the middle after the groove is formed. You could again shim the original template to establish the edges of the cut (but unlike above, that requires you to cut exact width, parallel-edged shims [2 x 17mm; 2 x 19mm]. For the full-depth cut, a small error here will not matter).

The challenge will be to find a 12mm bearing guided bit but with the 2mm clearance a 1/2" one (12.7mm diameter, 6.35mm radius instead of the specified 6mm), which is far more plentiful, will be OK.

Do a test run in the offcut of the MDF sheet first.

The way the rebates are dimensioned is misleading. It is the largestMake the template hit and miss at the corners and you don't need to measure anything, just make sure the side touching the hob packer is straight and the template has one side square to its face. dimensions of the entire hole that are critical. The 17mm and 19mm just say how far from the outer edge the full depth cut needs to be.

Hi, many thanks for your detailed instructions. Greatly appreciated
Could you maybe clarify a couple of things for me please? " Make the template hit and miss at the corners and you don't need to measure anything, just make sure the side touching the hob packer is straight and the template has one side square to its face". Also, could you tell me what length of router but you would suggest.
Thanks again.

 

[MikeJhn]

The router bit needs to be long enough to get through the worktop, but use the depth stop on the plunge mechanism to limit the depth of cut too 10mm each pass.

 

[ChaiLatte]

The router bit needs to be long enough to get through the worktop

The groove that requires the router bit is 5mm deep.

This one would do well, should he choose the bearing option:

https://www.toolstation.com/trend-14-template-profile-router-cutter/p41051

The large rectangle of material that needs removing full depth does not need routing full depth. Use the template to rout its outline maybe 3mm deeper than the groove, saw out the bulk and sand to the routed edge.

 

[ChaiLatte]

Make the template hit and miss at the corners and you don't need to measure anything, just make sure the side touching the hob packer is straight and the template has one side square to its face.

Have a look at the Trend template linked to in the post above (thanks to the original author). I was describing a home-made version of that. Its corners are hit and miss. It is made of four identical pieces and at the corners the pieces fly past each other not butt into each other. Made that way it can accommodate any rectangular size from zero up to 600mm x 600mm.

https://trenddirectuk.com/trend-varijig-varijig-system-adjustable-frame.html

 

[XTiffy]

I would start by using a jig saw to cut out the bulk of the waste and then jigs for a router.

 

[ChaiLatte]

I would start by using a jig saw to cut out the bulk of the waste and then jigs for a router.

If you cut out a big hole in the middle, what happens to that side of the router when you use it with the jig?

It will try to fall into the hole.

If both sides of the router are supported while it is being used, it has a much higher likelihood of doing a good job. Once all the router work is complete, then use the jigsaw to remove excess material.

 

[XTiffy]

Don't agree as you are removing small amount on one face it is much easier to control.

 

[Doug71]

I have no experience of flush fit hobs in wooden worktops but would be slightly worried that there is only 4mm clearance on the cut out as I have seen 600mm deep worktops shrink by more than this.

I would make sure the top is well acclimatised before you make the cut out, although unless the top is fastened down it might start cupping which will be a whole other issues for fitting a flush fit hob.........

 

[mal165]

Hi, my sincere thanks to all who have contributed and assisted me understanding what is required with this job. I'm much more confident now of tackling this. The worksurface is Minerva. Router bit purchased today but won't have time to try a dummy run for a week or so.
Thanks again, all

 

[Spectric]

If you are looking at getting a template made then maybe this jig from Benchdogs is the answer,

https://benchdogs.co.uk/products/router-template-jig

Not a cheap option but it is very well made and way better than the trend version and would allow you to easily adjust round the hob and route the rebate.

 

[Distinterior]

@mal165
If the worktop is Minerva, I hope you've got good dust extraction on your router coz it's real messy without it...

When routing out a Hob cutout in this type of material, the best way for you to cut an accurate aperture & rebate would be just to use 4 strips of MDF and hot melt glue them to the surface of the worktop to create your template size. A quick sand of the surface around the cutout area with 120 grit, then wipe the surface with DNA ( or the DNA cloths that may have come with your worktops...) to remove any dust, then stick your MDF strips in place.
The hot melt adhesive will hold the MDF strips in place on the worktop and will be easy to remove once the routing is done.

Then relocate & stick the batterns again to suit the rebate for the flush mounting Hob.

I've done this many times and it works well for a one-off situation.
However, I have a couple of routing templates I've had made for the flush fit Hobs that I fit on a fairly regular basis.
It made sense to me to pay to have them made, but as i said, for a one-off, the MDF strips & hot melt glue method will work fine....

Tim.

 

[mal165]

@mal165
If the worktop is Minerva, I hope you've got good dust extraction on your router coz it's real messy without it...

When routing out a Hob cutout in this type of material, the best way for you to cut an accurate aperture & rebate would be just to use 4 strips of MDF and hot melt glue them to the surface of the worktop to create your template size. A quick sand of the surface around the cutout area with 120 grit, then wipe the surface with DNA ( or the DNA cloths that may have come with your worktops...) to remove any dust, then stick your MDF strips in place.
The hot melt adhesive will hold the MDF strips in place on the worktop and will be easy to remove once the routing is done.

Then relocate & stick the batterns again to suit the rebate for the flush mounting Hob.

I've done this many times and it works well for a one-off situation.
However, I have a couple of routing templates I've had made for the flush fit Hobs that I fit on a fairly regular basis.
It made sense to me to pay to have them made, but as i said, for a one-off, the MDF strips & hot melt glue method will work fine....

Tim.

Many thanks for the advice Tim. I was advised by Homebase staff that installing Minervaxworktops was "certainly not a DIY job"! I've arranged for Minerva to machine the undermount sink recess and drainage grooves, so that really only leaves four cuts and two joints to be made. Is that beyond the ability of a competent DIYer I your opinion?