I refuse to use anything else when joining kitchen worktops!
These ZipBolt workshop connectors are FANTASTIC! I wish they were cheaper, but, as a professional kitchen fitter, I feel they are worth their weight in gold. Think of it this way: if you've spent 2, 3, 4, 500 quid or more on worktops, then don't you want to maximise your chance of achieving the best possible joint with the smallest possible gaps? Or do you want to penny-pinch a mere fiver and lower your chances?
ZipBolts can actually improve the quality of the finished joint because they are extremely rapid to tighten. This means no struggling to get the joint closed before your glue begins to gel. With old-fashioned generic worktop connectors (AKA 'dogbones'), they can take 3 or 4 minutes to be tightened (or a little quicker, if you use a ratchet-type spanner), especially when there is insufficient room to fully swing a 10mm spanner back & forth (this scenario happens more often than you might think, because sometimes worktops are 'trapped' between the room walls and the cabinet beneath is not always in a favourable position to allow good access to the connector bolts). With ZipBolts, however, the entire ZipBolt can be held on the tip of a cordless drill-driver (it won't fall off whilst the driver bit is inserted in the ZipBolt end, as the allen bit deeply locates within the socket in the ZipBolt). This means that no room is required to swing any spanner back & forth. It also means one can hold the cordless drill driver under the worktop, without needing to look at it, and WITHOUT risking the connector falling out of the worktop recess during tightening (although I will give you a helpful tip, at the end of this review), and therefore one can comfortably watch the top surface of the worktop, so as to ensure the worktop is aligned correctly and the joint closing perfectly, with no gaps. With old-fashioned dogbones the 3-4 minutes tightening them can lead to the joint not closing as tightly because the glue begins to gel/skin before it can be fully squeezed out. This is especially true with Colorfill, which, because it is solvent-based, begins to skin / gel extremely rapidly.
Speaking of joint adhesives/sealants, never use PVA with chipboard laminate worktops (even if it's waterproof PVA) because PVA is water-based and will consequently cause the chipboard to slightly swell, which will make the top surface of the laminate slightly raised - this does not go back down when it has dried - the worktop remains damaged forever. Be aware that there are some acrylic mastics marketed specifically for worktop joining which are also often water-based, and thus not the best idea. The same goes for water-based cartridge adhesives like 'instant nails', decorators caulk, etc. etc.. Please don't let anyone convince you otherwise - I've witnessed PVA ruin worktop joints on a number of occasions.
Because it is not water-based, you can safely use generous beads of transparent silicone if you like (enough to ensure 100% of the chipboard will be covered, when the joint is squeezed together, and then the excess wiped off the top surface (Wonder Wipes can make cleaning-up silicone much easier), but if you choose to use silicone, do make sure it's a high quality one and that it includes a fungicidal agent (there are many, many silicones on the market, but Dow 785 is, broadly-speaking, about the best widely-available sanitary silicone). Don't be a penny-pincher - buy good quality silicone if you want a good joint that looks good, lasts well, and doesn't decay or peel away easily.
An improved method is to apply a thin layer of silicone (about 1mm deep) to *BOTH faces of the joint*, using a spreader, covering only the bottom two thirds of the joint (and be sure to also leave some bare chipboard, with no silicone, 10mm from the front edge of the worktop), and leaving the uppermost 10mm of the joint (the 10mm nearest the laminate work surface) free of silicone (don't cheat with a bead of silicone - if you are choosing to do what I am about to suggest, then you want to use a spreader to control the silicone so that none of the bottom 2/3rds of the chipboard accidentally misses out on the silicone AND you want to control the silicone so that it doesn't try to squeeze upwards towards the top surface of the joint:
The upper 10mm of the chipboard (and the small area 10mm from the front edge) that has not had any silicone applied, can then have a generous 6mm bead of Colorfill worktop jointing compound applied to *BOTH faces of the joint* (you have used a spreader to control the silicone, but DON'T use a spreader on the Colorfil - if you have applied a generous 6mm bead to BOTH faces of the joint, there will be ample Colorfill to find its own way into everywhere it is needed, when you assemble the joint). Remember, you must work very quickly because Colorfill begins to skin-over very rapidly.
NOTE: Even if you are under a tight deadline, *ALWAYS* DO A TEST-TIGHTEN of the worktop joint *BEFORE* applying any adhesive / sealant / Colorfill; you want to be absolutely 100% certain that the joint fully tightens without gaps, BEFORE you stress yourself with applied adhesive / sealant / Colorfill). This combination of bottom 2/3rds with transparent silicone and upper 1/3rd (and front edge) with generous amount of Colorfill works very well, as long as you apply the silicone in the controlled fashion described, and as long as you apply the silicone and the Colorfill to BOTH faces, rather than lazily applying to only one face of the joint. You get a well-sealed joint and the benefit of Colorfill to fill any tiny gaps in the joint. After the joint has been cleaned-up using the little bottle of solvent that is supplied in the Colorfill pack, any remaining gaps in the joint can have a bit ore Colorfill rubbed-in and this then cleaned-up again with the solvent. One more thing: if you wish to, you can use a hybrid polymer sealant-adhesive instead of silicone. This means products like StixAll, Fix-All, 'Sticks Like' ('Sticks Like Sh*t' - honestly, that is the real name of it!), 007, ClearFix, and others.
As I mentioned earlier, never use anything water-based (PVA, acrylics, etc.), and (other than the little tubes of Colorfill I've been discussing, which do work appropriately for this task) never use a solvent-based mastic-type adhesive like GripFill etc., as they're not suitable for the particular task of worktop joints.
*I promised a helpful tip to reduce connectors falling out of the worktop recess during tightening. When you lift the FIRST worktop into place, on top of the cabinets, before you do this, you can flip the worktop upside down (place some cardboard on top of the kitchen cabinets so the laminate surface doesn't get damaged). Whilst this first worktop is upside down, you can insert all of your connectors into the recesses in the chipboard (make sure you only insert the 'dumb' ends of the connectors into this first worktop, so that the tightening nut (or tightening allen socket, if you are using ZipBolts) is hanging in mid-air, to eventually to be inserted into the recesses in the second worktop. When you are doing this, be sure to check that the connectors are loosened sufficiently that when the second worktop is lowered into place, the connectors will not foul / get crushed, but will freely insert themselves into the recesses of the second worktop, without hindrance. Obviously, you need to think carefully about which of your worktops will be the 'first' one, and which one will be the 'second' one to be lifted into place, because you want the second worktop to be the one that will have the bolt ends accessible to the tool you will be using for tightening purposes. It can be tricky gaining access to those pesky bolts, with some corner cabinets, so think this through, thoroughly! Anyway, assuming you've carefully figured out which will be your first worktop to lift into place, let's go back to the point where you flipped it upside down onto a piece of protective cardboard, on top of the cabinets. Whilst it's upside down, insert the 'dumb' ends of the worktop connectors into their recesses, and then you can sneakily drive a *SMALL* screw, diagonally, into each of the round recesses, in such a way that it 'traps' the bent metal plate of the connector in the recess. These screws should not be longer than 20mm, or you may risk flaking the chipboard (or, worse, going through the laminate surface on the face side!!). Alternatively, Unika make some plastic clips that trap the shaft of the connector into the shaft recess in the chipboard (that product is called 'EasiBolt'. The Unika steel worktop connectors are bog-standard dogbones - what you're actually after is the included plastic component that traps the shaft - in a best-case scenario, you'd rob these plastic components and apply them to ZipBolt connectors). You can use either tiny screws method or the plastic 'Easibolt' component method, and they are EQUALLY successful, so you don't really need to be buying 'Easibolts' for this purpose unless you prefer to do that.
Of course, if you're experienced, or simply confident in your abilities, you can choose not to use either of these methods, but I do recommend using one of these methods as they can make life much easier when assembling the joint, especially considering that the faster the joint is successfully assembled, the smaller the joint gap is likely to be, and everyone wants the smallest possible gap in their worktop joints, don't they? There's nothing worse than having a worktop joint loaded with adhesive/sealant, and the clock ticking, and then a joiner falls out of one of the recesses and you have to dismantle the entire joint, lift the worktops off the cabinets and rescue the bolt and re-insert it.
Lastly, some tips for routing the worktop joint, prior to assembly:
Never use speedclamps / trigger clamps / qwikclamps, etc. to hold the jig to the worktop - they are great for many tasks, but, for routing kitchen worktops, always use traditional screw-thread G-clamps. The reason is that G-clamps do not accidentally 'let-go' like other types of clamps sometimes do. G-clamps can also apply more pressure, to reduce risk of slippage, although one obviously needs to be careful not to overtighten as that may squash the chipboard or fracture the laminate surface.
Secondly, I recommend you buy a decent quality 12.7mm cutter, rather than a generic Chinese cheapo one, because cheap cutters are sometimes not accurately sized, but, more importantly, chipboard worktops and hardwood worktops are very abrasive and can rapidly blunt low-quality tungsten carbide. When a cutter gets blunt, it will chatter/vibrate more during routing which can reduce the quality and accuracy of the cut, put more stress on your router collet / bearings / motor, and even risk shattering the cutter (always wear goggles when routing!). Also bear in mind that even the best quality cutters should not be used to cut more than 2 or 3 complete worktop joints. That might sound extravagant, but routing worktops is brutally taxing on router cutters.
Always remember to cut worktop joints in several passes (10mm deep, then 20mm deep, then 30mm deep, then 40mm deep), as this massively reduces stress on the router cutter and the router itself.
When you use a router jig, you will notice that the 30mm guidebush does not fit tightly within the jig slot - you will find that there is a small amount of 'play'. When routing the 10mm deep, then 20mm deep, then 30mm deep, then 40mm deep incremental passes, try to apply a little sideways pressure so as to bias the router cutter AWAY from the final face of the joint you are routing. Only when the joint has been cut to full-depth should you make a final 'finishing' pass, whereupon you should apply a little sideways pressure to the router, this time TOWARDS the face of the joint you are cutting. This will give you the best chance of accuracy, as the cutter will sometimes vibrate / chatter during the incremental passes, so you want to save a nice smooth pass for the final finishing of the joint face. Incidentally, for those of you who are confident enough with a jigsaw that you can control it very well without risk of the cut wandering, you can rout the first 10mm-deep pass, and then switch off the router and carefully jigsaw along the middle of the groove you've just routed (using the jigsaw WITHOUT unclamping the routing jig). Once you've jigsawed off the bulk of the waste material, you can then resume your incremental passes with the router. This jigsawing method is only to reduce wear & tear on the router cutter, and is not strictly necessary, but is worthwhile if you are confident you can jigsaw without damaging the routing template.
Here's a major point: One of the most important things to understand is that when you rout a worktop (and this holds true for chipboard laminate worktops AND for solid timber worktops) is that you must ALWAYS rout in the direction of BEGINNING the cut moving *INTO* the front edge of the worktop. If you begin to rout by entering into the back edge of the worktop, and exit through the front edge of the worktop, you are 99.999% guaranteed to destroy the front edge of your worktop, because the rotation of the cutter blades will splinter the laminate or wood grain (therefore, it is sometimes necessary to rout the joint with the worktop upside down, to ensure the direction traveled by the cutter is correct). This is such a vital thing to understand! So much so that if you are confused by what I am describing, then please just spend a couple of hundred quid getting a professional to cut the joints. If you get this aspect wrong, you may waste several hundred quid with irreparably damaged worktops that will need new ones buying to replace them.
Lastly, if you choose to use ZipBolts, don't use an impact driver to tighten them - the right-angled gearing mechanism employed within ZipBolts is surprisingly robust, but it does have limits to the amount of torque it can withstand, so be sensible and only use MODERATELY high torque using a cordless drill-driver or manual allen driver.
I hope no one objects to me typing so much, here, but I sincerely wish whoever fits their own worktops to have the happiest end result.
With that said, I highly recommend spending a little extra to obtain these genuine 'ZipBolt' branded worktop connectors, as they significantly increase one's chances of success, and Axminster price them competitively, too. Just note that Axminster stores seem to have quite erratic stock levels of these connector bolts, so phone or browse before you travel to a branch to buy some.