Fuel tank wows

[sam011]

Hello all,
I thought I would clean my fuel system through, so out came the os fuel tank from my 3.4 s-type, removed the sender first. All fine, next the drain plug/Filter and that's when the trouble started, with spaners/hammer and anything else I could throw at it, it would not move. So after days I reluctantly took the tank to a garage down the road, two days and £40 later it was out. So a good clean out later, new parts in hand I try to fit the new drain/filter it threads in two or three turns by hand then a turn or two with the spanner before locking up with still loads of threads to go. So to the dilemma, was the old one cross threaded hence it would not come out? can you get a tap to rethread it or do I just keep tightening to the end or are they all like this. So any options or suggestions would be greatly appreciated.

[piman]

Hello Sam,

I think that you need to compare the old to the new to check that it has the same thread pitch. If that's OK then a tap is a good idea. Off the top of my head I would guess that it is a BSP thread, but hopefully someone will know for sure. A good source of taps and dies is a company called Tracy tools https://www.tracytools.com/ who carry a huge range and generally sell high carbon steel and High speed steel (HSS) versions. The carbon steel being much cheaper and perfectly adequate for a one off job. If you can accurately measure the thread diameter and the pitch of the thread they would identify the thread for you as well.

Alec

[sam011]

Hello Alec

Many thanks for your reply, this sent me off in the right direction and a chance meeting with a friend of a friend who works at a small
Engineering company had a look at both the tank and the drain plug. The result was that the tank had a shallow thread, this was re-cut and both fit together just fine.
Many thanks for your reply again and these things are sent to try us.
Sam