johnwill Posted December 2, 2020 Report Share Posted December 2, 2020 (edited) I have a rectangular Smiths Clock in my 4A, I think originally in 2000's and 2.5's ? In my wisdom.... I decided to take it out to fix it, and in re-fitting, trying to put the back plate on, i dropped both the thumb nuts for it. Couldn't find them, so took the H frame out as I thought they had dropped down one of the "legs". Found one, but the 2nd had vanished completely. Anyone know where I can get these from? They are a smaller inner diameter than the thumb nuts on the rest of the gauges, not sure what thread? 3BA, 4BA? Any advice welcome. I have some standard nuts to use if I cant get the thumb nut, but theyre not so easy to do up/undo from behind the dash. Thanks john Edited December 2, 2020 by johnwill Quote Link to post Share on other sites
tim hunt Posted December 2, 2020 Report Share Posted December 2, 2020 Bad luck John, these thumb nuts are a fiddle - whenever I remove the instruments I invariably manage to drop one of them but have always managed to find it. They are 3BA and readily available on Ebay. Tim Quote Link to post Share on other sites
johnwill Posted December 2, 2020 Author Report Share Posted December 2, 2020 Thanks Tim. I assume the nuts on the rest of the guages is 2ba? Quote Link to post Share on other sites
RogerH Posted December 2, 2020 Report Share Posted December 2, 2020 Hi John, I believe they are all an odd size - 3BA Roger Quote Link to post Share on other sites
johnwill Posted December 2, 2020 Author Report Share Posted December 2, 2020 1 minute ago, RogerH said: Hi John, I believe they are all an odd size - 3BA Roger Roger The thumb nuts on the instruments gauges, fuel, water etc are bigger I/D than the ones on my clock. (they slide straight down the threaded "bolt") The clock nuts are smaller. Are the guages 3ba? or bigger thanks John Quote Link to post Share on other sites
RogerH Posted December 2, 2020 Report Share Posted December 2, 2020 Hi John, I thought they were all 3BA but your comment has jiggled something in my head. The speedo and Tacho may be 2 and or 3 BA I'm sure I've come across both. Roger Quote Link to post Share on other sites
johnwill Posted December 2, 2020 Author Report Share Posted December 2, 2020 15 minutes ago, RogerH said: Hi John, I thought they were all 3BA but your comment has jiggled something in my head. The speedo and Tacho may be 2 and or 3 BA I'm sure I've come across both. Roger I think theyre the same thread, just larger O/D. The clock is smaller I/D... weird. Quote Link to post Share on other sites
tim hunt Posted December 2, 2020 Report Share Posted December 2, 2020 The thumb nuts on ALL my instruments are interchangeable with 3BA threads. Tim Quote Link to post Share on other sites
wish i could drive it Posted December 3, 2020 Report Share Posted December 3, 2020 i have just bought new aluminium thumb nuts for all my instruments on my car(1973 tr6) they fit on the speedo and rev counter but will not fit any of the small gauges. i have been told they are 3ba so that is what i ordered, so what is the thread on the small gauges? the studs are 4mm diameter. ian Quote Link to post Share on other sites
BlueTR3A-5EKT Posted December 4, 2020 Report Share Posted December 4, 2020 16 hours ago, wish i could drive it said: i have just bought new aluminium thumb nuts for all my instruments on my car(1973 tr6) they fit on the speedo and rev counter but will not fit any of the small gauges. i have been told they are 3ba so that is what i ordered, so what is the thread on the small gauges? the studs are 4mm diameter. ian Have you tried M4? here are plastic M4 thumb nuts. They should not ruin the metal stud thread! https://www.ebay.co.uk/itm/Black-M4-Plastic-Nylon-Knurled-Thumb-Nuts-With-Collar-14mm-Diameter/192180245758?_trkparms=ispr%3D1&hash=item2cbed5d4fe:g:NcIAAOSw7GRZDv6W&amdata=enc%3AAQAFAAACcBaobrjLl8XobRIiIML1V4Imu%2Fn%2BzU5L90Z278x5ickkfKe2vUidqHRg3XM2X2xOVOMFbwmsCcNl11KtuUI6NfxrixCG86L4S7qht5T3nJQ%2BHO6GZPCdJKnh5h4SXhL59Xnz4mI6gJIunGGgDHFC9u69PJh9neUXzMa9RDOOeA2wspDxm9FYEicy1pmxO6ApAZKbkBMamLhVxvrjwXIl8%2BuMyfb8dhKzOnM%2FZFD6vidyaejO2r%2BwkkgfKAfn3h4ZuXWLiQyWzNSgRYqX9W0fZLFw6FvWiR0aqqGmNQtWHvE9kq033l%2FyKkcEDcKsPNl63zW1fOsJ44h1vH6ixwHVOd7%2Fb4dQ2iOEABo67v65IXxcAkOge9Frfn3xXOI4bK%2BASfz%2Bq%2Fx8D3qOfol3v5zh1b5ViAWdwCweLkMOJkEItPjj%2Fb6cZ%2FvOmibFDUvnVqvGF0BkXNNHTuPlmvA4OElFWHgLkFuHntgKAlzZhSUyszjcQ4wXOJF6895bSXsPdcWYDZ21v9rd0KPVlwyE4HunXRwUZIRWUvYiK9sMWXMixXM9xATfaaNajEchCHi7ATtTu8ZKzsUSAW8NwHNmtjKgs8qciXqj20eVZ%2BVEafiPMU5ASwIfW1cETiQ1XxzB1hjWGutZT1i%2B45Fzefqi6HkJswmpgSYr8m7RK1ISvGNRJAeIyK6ohp2ETVvOYUCHUPqlA1lHJMiycuUuK7n0RD8KNXO8qBQAeSMSxEccsNWATYB9W2optUK2Y1JiFV5L85Uhfhmc5ElP8eZCtc5odaFRmhOSoaiK5P8qqNBHptH9LkPkCjoG5X49hEMTWY5NdgquVg%3D%3D|cksum%3A1921802457589ce99ea9f8b64fa4a4d948a8c25ca8df|ampid%3APL_CLK|clp%3A2334524 cheers Peter W Quote Link to post Share on other sites
RogerH Posted December 4, 2020 Report Share Posted December 4, 2020 16 hours ago, wish i could drive it said: i have just bought new aluminium thumb nuts for all my instruments on my car(1973 tr6) they fit on the speedo and rev counter but will not fit any of the small gauges. i have been told they are 3ba so that is what i ordered, so what is the thread on the small gauges? the studs are 4mm diameter. ian Hi Ian, that is interesting. The Moss WebCat shows all the gauges using the same nut on the TR6 On the TR4/4A it shows the same nut for the big gauges as the TR6 but they refer to 'small' nut for the smaller gauges. The OD is certainly smaller but I would have thought the ID was the same. Roger Quote Link to post Share on other sites
RogerH Posted December 4, 2020 Report Share Posted December 4, 2020 3BA screw OD is a gnats over 4mm so the M4 nut may fit in that respect. 3BA has apprx 36 tpi M4 has apprx 37 tpi Why would they use M4!! Roger Quote Link to post Share on other sites
johnwill Posted December 13, 2020 Author Report Share Posted December 13, 2020 (edited) On 12/4/2020 at 9:35 AM, RogerH said: Hi Ian, that is interesting. The Moss WebCat shows all the gauges using the same nut on the TR6 On the TR4/4A it shows the same nut for the big gauges as the TR6 but they refer to 'small' nut for the smaller gauges. The OD is certainly smaller but I would have thought the ID was the same. Roger My guages thumb nuts are the same ID and thread as the Speedo & tacho, but as you say, the OD is larger on the Speedo & Tacho. Looks like i'll have to use normal nuts on my clock, will be more fiddly than the thumb nuts, but only solution I think. Edited December 13, 2020 by johnwill Quote Link to post Share on other sites
stillp Posted December 13, 2020 Report Share Posted December 13, 2020 These any use? https://www.ebay.co.uk/itm/Smiths-British-Jaeger-Instrument-Gauge-Nuts-3BA-Aluminium-Large-x-2-/132429998235 Pete Quote Link to post Share on other sites
DaveN Posted December 14, 2020 Report Share Posted December 14, 2020 (edited) I think the 2 inch gauges nuts are tapped 8-32, the tacho and speedo nuts are 3BA, which is a few thousandths larger than 8-32, and 34-8 threads per inch. Edited December 14, 2020 by DaveN Quote Link to post Share on other sites
wish i could drive it Posted December 15, 2020 Report Share Posted December 15, 2020 just to add to the confusion? evidently smiths instruments, sometime in the early seventies switches to metric threads,in their wisdom they kept the same part numbers. so you could get a mixture, in my case the speedo and rev counter are m4 threads, but all the small gauges are 3ba. clear as mud. so you had better check your nuts carefully????? Quote Link to post Share on other sites
johnwill Posted December 27, 2020 Author Report Share Posted December 27, 2020 On 12/13/2020 at 1:55 PM, stillp said: These any use? https://www.ebay.co.uk/itm/Smiths-British-Jaeger-Instrument-Gauge-Nuts-3BA-Aluminium-Large-x-2-/132429998235 Pete No, 3ba is too big. Thanks anyway Quote Link to post Share on other sites
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