Worktop mitres

[Steve]

I'm going to attempt mitre joints on my grandma's new kitchen worktops. I'm going to hire a router and jig for a day. I have fitted two kitchens before, but always left the worktops well alone. Im feeling confident that i can do this now though.

The problem is the layout. See the photos attached. The way i see it, the only way to do the joints with 3m lengths is with one piece having two male ends as i have drawn in the second image

.

Is this simple enough to achieve? The only videos i have seen online show a female left, male right joint. I guess this is the preferred or easiest way to do it. I know i need to make sure the spin of the router is kept the right way around so it doesnt blow out the laminate.

The worktops are square edge gloss white.

Any other tips?

Thanks

 

[Deleted member 174758]

I think I'd have preferred to go for 4m worktops - that would make the job a lot easier than trying to get two male ends on one piece (it's generally the male end I adjust to take into account out of square corners)

 

[Steve]

I think I'd have preferred to go for 4m worktops - that would make the job a lot easier than trying to get two male ends on one piece (it's generally the male end I adjust to take into account out of square corners)

The way I was thinking of doing it was to do both the female ends and sink cutout, place them in position, then lay the long piece on top in situ to mark the under side at both ends. Would this be possible? I'm tiling the splashback so I've got about 10-15mm leeway in total.

 

[Deleted member 174758]

You need to realise that these jigs use a 30mm guide bush and a 12.7mm (1/2in) cutter so your marked out line will actually be 8.65mm off from the opening in the jig (Trend do a marking tool to deal with this offset). Secondly, are the units actually square? If they aren't it gets a bit more complicated because you'll need to adjust the angles of the male ends when you make the cuts. Whatever else I'd start by doing the small worktop to the left, then getting the left hand end of the double male top done - that will need to be routed from the back to prevent blow-out on the post formed edge. Once you've get that end sorted out it gets a bit easier

 

[Steve]

You need to realise that these jigs use a 20mm guide bush and a 12.7mm cutter so your marked out line will actually be 8.65mm off from the opening in the jig (Trend do a marking tool to deal with this offset). Secondly, are the units actually square? If they aren't it gets a bit more complicated because you'll need to adjust the angles of the male ends when you make the cuts. Whatever else I'd start by doing the small worktop to the left, then getting the left hand end of the double male top done - that will need to be routed from the back to prevent blow-out on the post formed edge. Once you've get that end sorted out it gets a bit easier

What I was going to do was do the two female joints and get those tops into position and cut the sink out while I can slide that top in and out.

Lay the long length on top/below roughly where it needs to be and draw a line at the left end to get the right angle. Cut the left male end. Then lay the top back into position with the left end in place and then mark up the right end to get the correct angle. Verify the measurement using a tape measure.

Am I on the right lines?

 

[Deleted member 174758]

Have you checked how square the units/walls are? I've yet to install a U-shaped kitchen which is square. Any angle adjustment at the corners is always made by packing the jig for the male joint (in my case I actually have a worktop jig which accommodates this). In this case I'd prefer to go clockwise round a kitchen dealing with the left hand male joint (cut from the underside face to prevent blow-out) before I dealt with the right hand one (which is cut from the top face) making it easier to mark-out and do any angle adjustment cuts. Your proposed method of working would result in the bottom only of the CENTRE worktop being marked-out for both the male joints - which is obviously not going to work as one of your lines would need to be transferred to the top face (error prone) if you are to avoid a cut on the underside which blows out the post-formed edge. Sink cut-outs and the like I always leave as late as I can to reduce the amount of handling (doing the cut-outs makes the worktops far more fragile). The sequence I'd follow would be something like this:

1. Cut LH worktop to size. Offer in and adjust/scribe as required
2. Cut female joint in end of LH worktop. Cut dog bone joiner cut-outs
3. Position LH worktop. Do any adjustments necessary to accommodate access to dog bones (e.g. cut-away nailer in carcass as needed). Temporary fix to prevent movement

4. Cut CENTRE worktop oversize
5. Cut male joint at left end of CENTRE worktop (this needs to be cut from the underside to prevent blow-out)
6. Offer in CENTRE worktop and note any adjustments needed to left hand male joint (highly likely there will be some)
7. Take-out CENTRE worktop. Make adjustments to left hand male joint in CENTRE worktop. Cut dog bones in left hand end of CENTRE worktop

8. Cut and scribe RH worktop to size. Offer-in to position. Mark sink and other cut-out positions in RH worktop but DO NOT CUT THEM OUT YET (as this will weaken the top). If OK lift out and cut female joint in end of RH worktop (this needs to be cut from the underside to prevent blow-out). Cut dog bone joiner cut-outs. Do not place on cabinets yet

9. Offer in CENTRE worktop again. Temporary fix in position. Masking tape across top where right hand male joint will be
10. Use offcut blocks to pack-up at both ends of RH worktop. Offer-in RH worktop, supported on packers and right hand end of CENTRE worktop. This sits ON TOP of the packers and the CENTRE worktop so that you can mark the cut position for the male joint. Mark the male joint position on the masking tape, then mark the offset (or better yet use the Trend tool to do it in one with no inaccuracy). Trying to do this with a tape measure, especially if the angle isn't bang on 90 degrees will result in a lot of bad language and inaccurate cuts. Lift the RH worktop off and set to one side

11. Detach the CENTRE worktop (remove temporary fixings). Pull out. Cut female joint in right end of CENTRE worktop. Getting this right is critical to a good fit. Cut dog bone joiner cut-outs

12. Do the sink cut-outs, etc in the RH worktop and position the RH worktop pushed back to wall as far as possible
13. Install dog bone fasteners in LH and RH worktops (may need masking tape to hold them in).

14. Ease-in the CENTRE worktop into position, pull the RH worktop across to snug the joint and check that the joints both line-up. Note any adjustments needed to right hand male joint (possibly required).
15. Lift out CENTRE worktop and if necessary make adjustments to right hand male joint in CENTRE worktop. Add adhesive and jointing compound to chipboard on all joints. Replace the CENTRE worktop

16. Tighten all the fasteners taking car the the joints are level all the way across (may need a dead blow hammer and a block of plywood to adjust this progressively from back to front). Because you have two male joints you will need to work quickly to do this before the glue sets (use a slow setting glue! Must be D3 or D4 though - D4 is waterproof and therefore better)
17. When it has all set do a final adjustment of the worktops into position and fix to the carcasses

At the end of that lot I'll say "e&oe"

The point is that in a non-square kitchen it can be a faff (and a lot of kitchens aren't square, especially U-shaped ones), and using short lengths of worktop (3m) is a faff as it forces you into an awkward position getting a good fit and makes using biscuits or Dominos to align a joint all but impossible because you have a trapped centre section of worktop. Be wary of thin (30mm worktops) as they tend to be cupped more often than 38/40mm ones. Any cupping across a worktop is bad news when trying to get a flat joint - it can be impossible to pull-out if more than a couple of millimetres - so if your tops aren't bang on flat (checked with a 4ft or 6ft spirit level) get them replaced. Hopefully your units will all be level end to end and front to back as any dipping will make getting a good joint impossible. Again I always check this before installing - you'd be amazed at how often they are out and I need to adjust units. I use a 6ft level and a 2 ft level for this task (lasers aren't accurate enough and I feel are subject to misreading in cases like this)