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Jubilee badge fixing holes


I need to clean the tank badge holes. Doe anyone know the size of the holes so I can carefully clean them out with a die.



Something tells me 3 BA  a distant memory..  Tracy Tools will probably have a tap for a few pounds.   Don't go too far in !!. I can remove one and check against my taps if needed. (not a die!)

Thanks Robert.

Yes I think a tap would be a better option.

I have noticed very little hole depth.



Ok, so I ventured out to the garage and found my tank with the chrome badges, I unscrewed them and found my thread gauges - retreated to the kitchen for a coffee and to find my glasses. None of the BA gauges fitted well, 4ba being the closest. I tried the metric set and found 0.6 a better fit. 

So I found the iPad and did some googling, 3.5 x 0.6 metric is close to 3.6 x0.66 which is 4ba. My guess is the PO couldn’t find 4BA and bought metric instead? 

So then next I looked up the part number - 20230A and googled that, result ... RGM sell them and list them as 4BA.

Should have looked there first!

So I can’t be sure but my deduction is that it is 4BA.



The holes in the tank left the factory with 4BA threads.

You want to use a tap, not a die to clear the threads. Taps cut internal threads, Dies cut external threads.

I find it better to remove the rust and dirt with a 1.5 mm drill turned by hand, then to use a tap. It gives you a feel for the hole depth.

Take care to engage the existing thread with the tap, so you don't cut a new thread. Use a bit of oil. If the tap gets at all hard to turn, turn it back and then forward again.

Accidentally break the tap in the tank holes and you will be in serious trouble.

Hope this helps


Hi John,

When you get the taps there will be a cone on both ends, used to grind them as they are too small to centre. I usually grind the one off the threading end to allow that extra thread to be cut. Take great care as Peter suggests.

Stay safe



Peter Holland is right, they started of as 4BA at the factory but in 50 - 60 years all sorts of bodges happen. I have a nice Navigator tank or was till the previous owner stripped most of the paint off and then tried to re tap the 4BA threads breaking a tap in the hole and then dinting the tank, I will have to grind it out and re tap and then straighten  the tank.

peter F


If they only want cleaning then try WD40 on a screw which holds a domestic light switch on its box. Use finger tightness only. Worked for me and avoided the potential damage of cross cutting with a tap or piercing the tank.


Be careful which screws you use, 4BA screws are not used in modern electrical fittings as these are metric not 4BA.



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