There may well be special screws but any of the usual modern variety will serve. You could use CA glue on the threads to improve grip. These screws are intended to be driven without pilot or clearance hole but are inclined to throw up a burr at the entry point which you may need to provide for.

Have a look on the Screwfix website.

Hello,

Guessing you mean chipboard or MDF, then any of the commonly available modern plated screws should be ok for using in the face of particle board. They are generally hardened twin thread, and waxed these days, you can even use them as self-tappers when needs must! A thicker gauge and pilot hole may give the best result.

The more specialist “HiLo” or “Carcass” screws are meant for use in the edges, as are “Confirmat” screws, all these types are usually only available in a couple of lengths though.

Mark.

I agree with using wood screws but I think you get a stronger fixing with a single thread.

I’m assuming the bench top is made from particle board as used on commercial desk furniture. Therefore use particle board screws, available from your local hardware store.

The main difference between woodscrews and chipboard screws lies in the threads which, on a chipboard screw, run all the way along the screw’s length to the underside of the head. One notable difference is that their grooves are typically asymmetrical to allow for better resistance against pull-out. They also usually have thinner shafts that enable installers to screw them into the necessary materials more efficiently than regular screws.

Drill a clearance hole thru the steel frame and a pilot hole in the bench top, slightly smaller than the minor diameter of the screws.

Most chipbpoard or “carcase” screws will not be long enough to go through your 50mm timber and then into the worktop enough. I can get through a few 1000 a year but that is joining 18mm material to other chipboard. They are also designed to go into the side of the board not the face.

Screwfix Turbo will do the job as will Toolstations Screw-tite or Screwfix Goldscrew if you prefer Pozi head. In both cases I would suggest drilling 5mm clearance holes in the framing so the screw pulls the worktop up tight and there is no risk of jacking. No predrilling of the worktop.

I don’t think I have ever seen kitchen or bathroom worktops held down with inserts, always a csk screw through the front rails and small pan head at the back which generally uses angle brackets on flatpack or solid carcases will tend to be same as the front fixing. Carcases will give up long before the screw pulls out of the worktop.

Was talking about some roof structure modifications with the Structural engineer I usually empoy a few months ago and when I asked if he wanted bolted connections he said No, Timberlok screws will do and that he seldom specifies bolts and timber connector washers between these days. So that is what was used, driven straight in with impact driver and no pilot hole, the plain shank allows the thread in the second timber to be pulled up tight.

Sounds like Unistrut to me

Here you go bit of Unistrut screwed to an offcut of 40mm worktop. Angleplate and G clamp holding a 56lbs anvil to it.

just the ONE 5 x 60 screw screw with a spacer so about 35mm into the worktop.

I assume you will use more than one screw in which case unless your frame is bolted to the floor when you try to lift by the worktop it should stay attached. I suppose the differences are from those of us that work with wood for a living and those that don’t. Same people who said the stand for my CNC was no good yet now several years since and a lot of work done with the machine and no problems with the screwed together stand. Mark, Ega and myself have said modern woodscrews will do, we work with wood.

Coming back to pull out loads etc, it’s a long time since I have done strauctural calculations so better to just use a practical approach

The first post and subsequent reply relate to holding the worktop down to the frame and then being able to lift the frame by the worktop.

Holding the top down to the frame really puts no load on teh screw save for resisting a bit of possible cupping

Lifting the frame by the worktop will put more load on the screwed joints. As my photo shows a single 5mm screw will hole 60lbs( anvil, clamp, angle plate) so lets say 25kg per screw. You don’t say what size your frame is but lets assume a 600 x 1200 with one cross member in the middle. Put screws at 200mm cts along the five frame members as that is a total of 21screws.

21 x 25kg = 525kg so even if you could lift that much it is unlikely that the screws will pull out before your arms come out of their sockets.

Now you have said you want to put “heavy” equipment onto the bench. As I have said in this situation the load is all downwards so the screws really only stop the worktop sliding off the frame if you wheel it into soemthing and stop suddenly so no really worries about screw loading there.

Main thin for the last issue is to ensure loads go directly down through worktop, to top frame which sits on the uprights which sit on the casters then all loads are taken by the compression of the materials not by any joints. Most likely failure of a structure like this would be twisting due to lack of triangulation rather than any component failing under compression loads.

As for bolting through the whole thing just watch if there is coolant splashing about as you don’t want moisture getting into the chipboard. Also if counterboring and plugging the holes you will then have your bolt head bearing on the less dense mid layer of the chipboard and not the denser outer layers.

Here is something supported by unistrut, soliid glass basins are 50kg each, ceramic top , metal draw runners and several sheets worth of board, glass fronts and overhang when open. 6 small screws hold it to the horizontal unistrut members and me and my glass guy stood on it to fit the mirrors so downwards loading needs minimal screwing. Though I did not use plugs and screws to hold the unistrut cantilever brackets to the wall behind. All to do with thinking about what loads here are and how they act.

On 12 August 2024 at 18:12 Andrew Tinsley Said:

Hello Jason,

 

Not being a woodworker, I am not confident that simple woodscrews are going to do the job.

 

I had hoped that my photo showing a screw supporting 27kg would give you some confidence. If you use the amount of screws I suggested you will only be hanging 8.5kg off each one when you lift the 180kg frame. As worktop is being lifted by the jack it’s weight does not need to be included in what the screws are lifting.

I have a related problem with chipboard and screwed fittings. My kitchen cupboards have simple knobs on. The knob on one cupboard, for some reason, is often catching on a trouser pocket and the screws on one hinge mounting have come loose – pulling straight out of the board. It is fixed into standard 16mm or so board. As it happens, there is an additional facing board at that point so I replaced the screws with longer, to go into both boards. These have now come loose – although, curiously,I haven’t actually torn a pocket yet as the screw fixings are weaker!

What would the committee suggest as a fix? Drill for screwed inserts? I had thought of using a hinge cutter to make a recess to take a hardwood plug glued in. Clearly, the original “screw into chipboard” fixings were not adequate in this case!

Many thanks, Jason – looks like a trip to Screwfix is called for! Quick tweak to hinge adjusting screws and job’s done. Haven’t come across these before but always happy to hear from a professional.