Tool for recessing screw head on steel trunking cover

Your trunking probably uses some variation of the dzus fastener (link to about 3 pages of them, just keep scrolling down.)  so then the correct size of  countersinking punch to suit will probably need the fastener style in the description.

(some examples of punches - a US firm with nice pictures, not a UK supplier)

I never cease to be amazed at the number of incompatible but similar variants there are. If you can post a photo we may do better to narrow it down.

Mike.

Sounds like you need a nut, a bolt and some correctly sized washers. Thinking small washer one side slightly bigger than the screw head. A big (penny) washer the other side with a hole that is bigger than the small one on the other side. Then a few more washers to fit the nut/bolt head. Once centred you can glue them together.to make the two halves. 

I wonder what effect the countersink punch would have on the paint or galv finish?

I suspect the more usual solution is just to use an offcut of lid and cut to size so the holes are where you need them. Or is the problem more sophisticated than that?

   - Andy.

Thanks for the suggestion.  I think the washers would present too sharp an edge and probably act like a Q-Max punch.  If necessary, I can make a tool by turning on my lathe.  Just thought it would save time and, probably, money, to buy the correct tool ready made.

Galvanising should be self healing.  It isn't always possible to use sections of lids that already have one fixing turnbuckle.  In any case, all sections should have a turnbuckle near each ends and 3m lengths have the fixings too far apart for short sections..  If you are worried about the finish, cutting and drilling would be more of a concern.

Thanks.  Haven't seen the tool or turnbuckle - so far - on the Dzus web-site.

This might be a silly question but do you need to actually match the turnbuckles or would another type work?

I’ve had to fit extra turnbuckles to some legrande trunking recently and it was just a case of drilling the right size hole in the right place and clipping it in. I’ve used them on another make of trunking too and seemed to work fine on that as well. 

Legrand trunking uses those spring loaded click in fixings.  Two in every position.  Nice but expensive.  I’m using Unitrunking as I can obtain it at a good discount and the turnbuckles are cheap.  I suppose I could tweek the bar on the turnbuckle so I don’t need the dimple, but it would be good to have them all looking like the originals.  A matter of professional pride really.

I drill the correct size hole, place a suitable size socket....sorry can't remember which size............underside of the lid, central to the drilled hole and from above ' attack' with a small ball pein hammer............works a treat and no it does not damage the galv.........................unless your buying cheapo cheapo trunking...........the kind you can spit through