oil cooler leak

After getting through 5 o-rings trying to stop the leak I managed to somehow cross thread the bottom union that bolts the oil cooler pipe to the rad.
Before I go out and buy yet another new rad and cooler pipe (current one is only a year old!) any other suggestions as to how to sort?

Have tried an entire pack of quick steel epoxy putty but it's still leaking

That's a no then

are the unions not removeable on your rad ?

Nope looks welded on

Well it's just a male thread on the rad

thread look like a thread file will help or very poor ,pipes not expensive

Never heard of a thread file before shall have a look thanks

Just my 2 cents worth, if bodging it with plastic metal or similar has not worked and you dont have acess to a lathe etc then it looks like new parts is your best option, it would be possible for a rad specialist to braze on a new union of course, but they might have to cut off a union from a used cooler as they are a bit special. If the thread is not too bad on the rad you might be able to get the pipe union to grip it, if it was squeezed a bit smaller, that could be done in a 3 jaw chuck maybe, if you had access to one?

My oil cooler pipes leaked where the rubber joined the metal pipe, they would twist in that joint quite easily when they should of course not twist, just 16 years of vibe i suppose, the pipes hold full oil pressure I was told on this forum, so joints need to be pretty good to take the pressure, and heat. I just hope the brit part eplacements last .....they look quite cheap in the crimped joint area, compared to the oem ones.

Sack off the cooler and join the pipes together

I am binning my oil cooler and pipes and using the bosses on the filter housing for gauge senders. Plan for next summer is to bin the standard IC and rad and fit custom alloy ones

Cheers folks, looks like I best fit another new rad, have 600mile round trip for Christmas and have my 4 month old daughter with me so don't want to take any risks