Hole size before galvanising

[bonepyro]

I am planning to make up some frames from universal beam, which will bolt together using M10 bolts.

The frames will be sent off for galvanising, but having never had anything galvanised before I am unsure what size hole would be required to ensure the bolts will still fit afterwards.

Can you share your advice please.

Also if the parts are 127 x 76 beam, is that likely to distort during the process?

 

[rikrobson]

Are they quoting a thickness for the galvanising? If so then the hole needs to be twice this bigger in diameter ti give the same clearance. If you don't then the Galv should be soft enough not to worry the bolt too much and just hit it in the hole.

 

[rtbcomp]

I'd drill the holes to suit the bolts as normal and ream them out when they've been galvanised. There's no guarantee that the centre of a galvanised hole will be at the centre of the drilled hole.

 

[Kent]

I tend to go up another half mm on clearance size but often you need to get a file out as blobs close things up a touch
Drilling afterwards just removes the point and clearing with a drill? Well it dont care if it all comes off the good side

M10 seems a bit skinny for the material chosen but hey I don't know what the plan is

 

[Welderpaul]

There's everything you ever need to know about galvanising here

 

[WorkshopChris]

As far as i am aware with structural its normal to allow 2mm on a hole diameter. Never seen any problems with fit up other than any odd lumps that will chip or file off. If your tolerances are tight you may have more problems with any possible twisting or movement from the galv process than the extra zink inside the hole.

 

[Kent]

Zeus guide gives you the excepted clearances
The exceptable for m20 is not the same extra as on m8 for obvious reasons

 

[bonepyro]

Thanks all for your input, think I know which way to go now.

 

[wookie]

I tend to go up another half mm on clearance size but often you need to get a file out as blobs close things up a touch

I went up a half a mm but I still had to clear some of the holes afterwards, the 4mm holes I'd done for split pins completely closed up and needed drilling out.

 

[Kent]

I went up a half a mm but I still had to clear some of the holes afterwards, the 4mm holes I'd done for split pins completely closed up and needed drilling out.

Yeah, I never send stuff to galv with iddy biddy holes like that
Regular enough I will run a 11.5 to take m10 and not have clearance for m 8 without the file

 

[wookie]

Yeah, I never send stuff to galv with iddy biddy holes like that

Oh well you live and learn, it was the first time I've sent anything for galvanizing, now I know for next time

 

[Kent]

Oh well you live and learn, it was the first time I've sent anything for galvanizing, now I know for next time

If you don't do some stuff wrong you never get to remember your mistake

 

[dannyp]

m10 seems small but hey

the usual is m16 bolts and 18mm holes

 

[Kent]

Wookie is on 4 mm! The usual? Usual for what? More than structural steelwork for buildings gets galv

 

[dannyp]

well the OP is on about makeing frames out of universal beam its small beam at 127x75 but i would have thought itd want more than m10's

 

[bigegg]

well the OP is on about makeing frames out of universal beam its small beam at 127x75 but i would have thought itd want more than m10's

If you drill two 18mm side by side in a 75mm wide beam, youre removing half the metal in that cross section - and each hole would only be 12mm from the edge (amd each other)
Idve thought m10 /12mm hole would be the limit personally