Parts not fitting after galvanising

[Rgillard]

Hi All,

I have recently built a cattle crush for an animal weighing scales for a friend. The crush had to be mobile. It was designed so that the panels all fitted together with 1" solid bar sliding into 1" ID pipe. Before galvanising the fit was good. We ground the solid bar down so it fitted nicely. We were expecting to have some fit issue after dipping. Im just wondering whether anyone knows of a cleaner way to get the fit back rather than grinding and filing? I know its a long shot but its worth asking.There is 8 total pins and it will require a lot of manual filing.

Regards,
Ronan

 

[jenkinsph]

Hi All,

I have recently built a cattle crush for an animal weighing scales for a friend. The crush had to be mobile. It was designed so that the panels all fitted together with 1" solid bar sliding into 1" ID pipe. Before galvanising the fit was good. We ground the solid bar down so it fitted nicely. We were expecting to have some fit issue after dipping. Im just wondering whether anyone knows of a cleaner way to get the fit back rather than grinding and filing? I know its a long shot but its worth asking.There is 8 total pins and it will require a lot of manual filing.

Regards,
Ronan

Would 3/4" pipe be strong enough? That would be very close to 7/8" outside diameter and could be galvinized too.

 

[o2batsea]

Next time smear silicone on the inside where the pins go before you dip. Second, be a total SOB with the galvanizers, be sure they are clearing slag before and during your dip or else you'll have snot balls everywhere.

 

[Scooby074]

I dont think there will be an easy solution other than grinding off the galvanize. You can recoat the ground areas to prevent rust with zinc spraypaint which wont build thickness like dip.

Can you take it out of the bore with a 1" flapwheel? They work pretty quick

 

[BHD]

Drill bit or reamer. if one could find one of those little step drills the right size on the large diameter,

 

[Craig Clayton]

I was told a story by a former sister in law, her father was a foreman in a large galvanising plant. A large order of nuts and bolts came in for galvanising that were intened to be used in the large hydro towers.
The dipping plant put on the proper amount of galvanising as per spec. When the bolts went to be used up in the towers the crews could not turn they together.
The person who speced the bolts did not order under sized bolts and oversized nuts to allow for the galvanising.
You are not the first to get caught in this trap.

Craig Clayton

 

[crash325]

My new trick.

Throw them in a cement mixer with a bunch of coarse sand and fine gravel.

Have a beer and listen to the "Music". :thumbsup::laughing:

 

[Renze]

Very easy, three ways (i worked at a trailer builder, we galvanised everything )

1. smear copper compound (copper grease) on the threads. The grease will evaporate but the ground copper in it, will stick so you can pry off the zinc shell because it didnt melt into the steel itself.
2. use a torch to heat it (galvanising is done at 450ｰCelsius) and then brush it off with a wire brush.
3. inner threadholes that didnt get copper grease in them were cleaned with a hand threader.
4. for parts like hinges, we used 1mm oversize.

As mentioned by someone, for electroplating the layer is very thin (couple micron) so no issues. For hot dip galvanising which puts on a 50 times thicker layer, there are special undersized bolts (or oversized nuts ?) for this purpose.

 

[Rgillard]

Thanks everyone for your responses. I ended up using a combination of flap wheel , flap disks and 1" grinding balls which allowed to me remove the galvanise from inside the pipes. I also had three tapped holes that I put bolts into before the galvanising which were then impossible to remove. On further thought that is what we do at work for painting but its not such a good idea for galv. Its very easy to run a tap through a hole to clear it out. Anyway we got the job finished and the customer is thrilled with the outcome. Thanks again for the feedback. I will always know how to prep stuff that is being galvanised which is a hard lesson now but will stand to me for the future.

Ron