How thick is a typical galv coating

[fizzy]

I am making up a sliding bracket to go on my trailer - basically 2 pieces of angle iron sliding along a large bit of box section.

How much clearance do I need to leave if I have it galvanised?

 

[fizzy]

And no I am not going to try and weld rectangular aluminium box to 15mm steel plate!

 

[ronan]

Its fairly thick Fizzy, but i cannot give you a dimension. We used to have stuff galvanised dipped a lot in work years ago, and would have to smooth it down with a flap wheel in the grinder to get parts to fit. I don't remember anyone actually grinding through it, and there were some right twits working there.

 

[Munkul]

we ask for
"Hot dip galvanized zinc protective coatings to BS EN ISO 1461:2009" which is a nominal 85 micron coating.

However it can be anywhere from 0.1mm on long flat sides etc to 1mm plus in flange holes, etc. Holes need reamed out, some bases need a run over with a flap disc.... some don't.

For the insides of box section I'd say 2mm each way clearance would be on the safe side. i.e. 1mm per side

 

[Luke]

As above. I think you'll regret leaving anything less than 1mm per face.

Being pragmatic, 2 mm really doesn't matter. Neither would 3 or 4 mm. Both less of an issue than a binding bracket.

 

[Gareth J]

It's mad the level of clearance needed to keep parts free after dipping. Especially if it's a longer bit like that and not just a bit of bar in a hole. If you're willing to smooth out knobbles it could be tighter but the above suggestions sound good.

Alternatively, if you need a good fit, maybe you could make one of the bits of angle bolted, so you can adjust it to get it nice.

 

[fizzy]

The bracket can be quite loose really. It will very rarely be used to move the trailer body back and fore for perfect balance.