galvanising hole thickness

[brooker2008uk]

Was just wondering if i was using a 12mm bolt thick, what size would i need my hole to be if its getting galvanising

 

[Welderpaul]

14mm

 

[madkayaker]

You might find it skins over without it being much bigger that the bolt head. Paul posted when. I did if he says 14 then go for it

 

[Welderpaul]

Holes smaller than 5-6mm may skin over. Thats why vent holes should be no smaller than 8mm.

Always drill/punch bolt holes as per normal standards whether the steelwork is to be galvanised or not. The loss of diameter on the hole is negligible.
M8: 10mm, M10: 12mm, M12: 14mm, M16: 18mm, M20: 22mm etc.

 

[madkayaker]

Good to know I've only had small things with small holes done and the holes has skinned over

 

[Hitch]

14, as Paul has said. Take the time to deburr the holes too, the galv likes to stick to burrs and sharp edges.

 

[brooker2008uk]

bearing in mind a door will be hinging of this as well and i do not want slop or wobbling about so would 14 be ok

 

[madkayaker]

Done up right can't' see any issues

 

[brooker2008uk]

yeah suppose 2mm isnt too much slop with 12mm bolt

 

[Hitch]

Depends how its being used....? As a pivot?

Nothing to stop you drilling it out after galv.....

 

[Welderpaul]

Drill it 10mm, then redrill 12mm after galv.
An M12 bolt will pass snuggly through a 12mm hole with no slop.

 

[nickk]

Drill it 10mm, then redrill 12mm after galv.
An M12 bolt will pass snuggly through a 12mm hole with no slop.

And don't worry about breaking the zinc surface as there's sacrificial action protecting the newly exposed surface.Bit like a cut wound bleeding & then scabbing over!

 

[brooker2008uk]

I understand but when fabricated i won't be able to get a drill to. So wondering what size i should drill the holes before galvanising

 

[nickk]

I understand but when fabricated i won't be able to get a drill to. So wondering what size i should drill the holes before galvanising

14 mm to be on the safe side.

 

[brooker2008uk]

so it shouldnt be sloppy are anything when rotating sure it shouldnt