Bonding steel to steel

[PeterC]

At long last I've found a tuit to start putting a new top on a bench (I was looking for a round tuit and the bench is sqauare - no chance!).

It's 2' square, made of 2"x2"x¼" angle iron. The old topwas 16 ga. steel and has been outside for 25 years, so it's done well. It's off and now I need to grind off the 2 remaining strips that are welded on.

The new top is thicker (4mm - sorry about the units) and I was thinking of fastening it with st. st. csk screws (not tapped - a 5mm tap in angle iron seems asking for a game of snap) with sticks-like-witney-to-a-blanket filling the interface underneath. I'm just not too keen on the slots/recesses in the heads as they'll hold water. Trouble is, I use this for all sorts of rough work, so I'm not sure if any sort of adhesive alone would be strong enough and withsatnd impact. Any suggestions please?

[Bob Minchin]

Screws and just fill the heads. Wax, if you think you will ever want to get em out or a scrape of car body filler if not.

[Dave Plowman (News)]

It's quite common to bond steel to steel on cars these days. Try a decent motor factor.

[LumpHammer]

If you've got some money spare, this sounds like a perfect excuse to buy a welder. A cheapish stick welder should do. Also, the bench can be used as a welding bench when it's finished.

[Nightjar]

Not with care and a decent tapping lubricant, such as Rocol RTD. Of course, with a 4mm thick top, you have enough depth for a countersink to suit M8.

If you don't want to / can't do the obvious and weld it, why not tap the top and put bolts up through the angle iron? You can the grind them flush to the surface and have no recesses.

[Roger Mills]

How about tapping some holes in the top, and screwing up into them from beneath? Then grind the protruding screws flush with the top surface.

[harryagain]

Weld it on. Why bugger about?

[PeterC]

Ah, car body filler?

[PeterC]

Never really had a use for a welder, but your mention of welding has reminded me that there's a neighbour 50 yds. away who repairs cars. I'll ask him how much for 8' of welding. Should be an easier job than weldin tinfoil on cars.

[newshound]

Because if you screw it on from underneath you can turn it over and use it again when it gets knackered, and then replace it easily.

[PeterC]

Bloody good idea - lateral thinkingX2! The steel plate will be easier to tap, as angle iron has little hard bits in it. A M5 thread in 4mm will give a nominal 5 threads which, with gluey gunk underneath, should hold it 'forever'*

*'Forever' in my case, being from OAP status to zero.

[PeterC]

Agreed, Harry. If possible I'd like to have the whole lot painted and sealed to the frame, so welding would bork any paint under the sheet. Still the neatest method though.

[Dave Plowman (News)]

No.

[The Natural Philosopher]

that or a high temp epoxy.

[PeterC]

Good point, but the old one, at less than half the thickness, lasted 20 years realistically; it's been deteriorating for the last 5 years or so. If I am still active in 30 years...

[PeterC]

er, why? Too brittle?

[Dave Plowman (News)]

Proper stuff for the job. Even on a car as old as my SD1, things like the door skins are bonded to the door frame, so it's not exactly new.

[PeterC]

OK, I might suffer a visit to Halfords.

[Dave Plowman (News)]

I'd be more inclined to seek out a motor factor who sells car paint and associated products.

Halford seem to be doing less and less car stuff - they no longer appear to stock brake pads. Except for bicycles.

[The Other Mike]

Sikaflex 255. As used for bonding windscreens and holding together one well known make of fibreglass vehicle