Fuel tank sender unit

[smiffy]

I have a sheared set screw in one of the mounting holes for the fuel tank sender on my Mk2. The screws that came out intact look a bit tatty. I plan to clean up the mounting holes with a plug tap and replace the screws, and I also need to extract the sheared segment. Does anyone know what thread size these screws should be? I estimate that they are 4 BA - the screw diameter is 3.4 mm (should be 3.6 mm for 4 BA or 3.2 for 5BA) and the thread pitch is 38 TPI estimated with a Unified pitch gauge (should be 38.5 for 4BA).
Best wishes, David

[ecosselynx]

Hi David

Just took one of mine out, it measures 3.4 mm or 0.135 inch in old money. 4 BA shows an OD of 0.1417 inch with a pitch of 38.46 TPI, but my screw is petty worn! I ran a tap into the thread, although the size is worn off it it must be a 4 BA as a 6 BA is to big and 3 BA to small (sorry don't have 5BA to try).
Hope that is of some help to you.

[smiffy]

Thanks for the prompt reply John. It does sound as though 4BA is correct; although the diameter is not quite right it may be that the screws are a bit worn. I'll give it a go with 4 BA and see how I get on.
Best wishes, David

[smiffy]

Finally sorted - the correct size is No 6 UNF - 3.5mm x 40 TPI for anyone else that might need to know. The 4BA tap would not engage in the mounting hole, and when I tried a 4BA die on an old screw it took a reasonable amount of metal off it. The 6 UNF tap worked perfectly and the sender is now reinstalled in the tank. One step closer....
Best wishes, David

[piman]

Hello David,

that size you quote doesn't sound right, especially the mixture of metric and imperial.
I think that it's normally given as 6-40 UNF and has a diameter of 0.138". I think the 6 refers to a wire gauge size, possibly just American?
I expect any of the specialist nut and bolt suppliers would stock them?

Alec

[smiffy]

Hi Alec
Sorry, my vernier calipers are metric. Your dimensions are correct.
Best wishes, David

[stuarthardy]

That's interesting. I've just had the same problem with my E-Type sender unit and fitted 5-44 UNF screws, as per the parts manual. Couldn't get the correct cheese head screws so had to use cap heads.

Funny how Jaguar used slightly different screws from model to model.

Regards

[sweller]

Couldn't get the correct cheese head screws so had to use cap heads.

I've found this company very useful
http://www.namrick.co.uk
No connection, except they're located five minutes from me.

[stuarthardy]

Yep, they have supplied most of the fasteners for my E-Type. They are good, and very responsive. Unfortunately, there aren't too many places that do the smaller unified screw sizes.

I used A series spares in the end and they are absolutely brilliant in their fastener availability and prices (especially compared to the Jaguar specialists). As ever, no association with the above mentioned etc.

Regards