galvanizing over a captive nut

[Kent]

Seeking guidance from someone who might do a lot of this day to day. Need to galvanize a frame but parts of it will have M16 captive welded nuts, so obviously the thread and even some of the clearance hole will receive a fair amount of molten zinc during dipping

Plan is to run taps and if required a drill through prior to tapping - post galv! Is there a better way or something else I should do to make the process easier? My Galvanizers (the only ones for 50 miles are rough numpties BTW)

 

[steve t]

Ive cut bolts down so their flush with back of nut and put them in before dipping, was suppried how easily they came out leaving a clean thread, might be worth a test piece to see if it works for youre situation.

 

[MoreWellie]

we have worked the other way and just run taps through post galvanising purely on the basis that there may be some galv left in the threads

most of our threads have been 6mm or 8mm so with M16 there should still be a fair hole left but I appreciate it might take a bit more effort to put the tap through

 

[Mr shiney]

I have tried both tapping and leaving a bolt in. Both seem to work perfectly well. Taking the bolt out afterwards is a lot quicker than running a tap down!!

 

[MoreWellie]

don't forget that any enclosed box sections need vent holes to allow air out (and presumably galv in and out) so if the only holes are your M16s then you may need to leave them empty anyway

 

[dobbslc]

Drill the plug bolts!

 

[Peloquin]

We do hundreds of m10,12,16 and 20.
All we do is run a tap down them after.
Using a set screw/bolt just means time putting them in and taking them out and I find quite a few nuts tend to bind onto a bolt after welding unless re tapped anyway.

 

[Hitch]

We do hundreds of m10,12,16 and 20.
All we do is run a tap down them after.
Using a set screw/bolt just means time putting them in and taking them out and I find quite a few nuts tend to bind onto a bolt after welding unless re tapped anyway.

100% Agreed.
People tend to get their knickers in a twist about the thread then not being galvanised... not sure if they realise galv nuts are tapped after galving usually.

If its captive nuts in galv, are the bolts galv too? Remember spun galv bolts don't tend to go into standard thread clearances, taps are available to suit galv bolt clearances.

 

[Kent]

No the bolts will be electro plated zink and obviously fitted after I re-tap the captive nuts

Thanks I knew someone would do s lot of these on a regular basis week in and out

 

[Parm]

I suppose it really depends on the application, if a fine tolerance is required then may be not, but if it's something General purpose the why not tap holes after halve and crack on. Why over complicate things ???

 

[cianh91]

We used to do a lot of this a good tap and you be grand