boggie Posted February 2, 2009 Report Share Posted February 2, 2009 Hi All, When we separated the engine from gearbox we found that there was a right old mix of bolts / set screws / etc of varying length and some missing! Can one of you kind chaps tell me what size / type I need? Ideally I would like to fit zinc plated if anyone has a source? I have the through flange starter fittings etc, I just need the rest. They look like 5/16 whitworth to me, is that right and if so, what length do we need? Cheers, Ian Quote Link to post Share on other sites
Rhodri Posted February 2, 2009 Report Share Posted February 2, 2009 I think that your Whitworth thread is probably UNC. There are a few different sizes, and studs if I remember, -I got the lot from Moss. Rod Quote Link to post Share on other sites
TR 2100 Posted February 2, 2009 Report Share Posted February 2, 2009 Hi Ian, Engine to gearbox fixings are all studs, UNC into the block, a short length without thread and a UNF thread for a nut. Can't give you an exact length - just what you need, but not too long or you'll have trouble locating the gearbox back on the engine (assuming an in situ change - obviously no problem if both units are out of the car. AlanR Quote Link to post Share on other sites
gnotte Posted February 3, 2009 Report Share Posted February 3, 2009 Ian, take a Moss parts catalogue on the external gearbox page, record the part number and the quantity, then go to the hardware & consumables page, near the end of the catalogue and from the part number you will know the thread, length and diameter of the screw or bolt you need. If you haven't a part catalogue there is one online on the Moss site. Bye, Guy Quote Link to post Share on other sites
BrianC Posted February 3, 2009 Report Share Posted February 3, 2009 I think that your Whitworth thread is probably UNC. There are a few different sizes, and studs if I remember, -I got the lot from Moss. Rod On a totally non-TR job last week, I visited a local fastener stockist looking to match up what I believe to be a Whitworth coach-bolt and he told me that BSW and UNC threads are the same. Didn't actually have the size I needed in stock though Quote Link to post Share on other sites
jean Posted February 3, 2009 Report Share Posted February 3, 2009 As far as I know there is a slight difference between BSW and UNC, also there is no doubt that they can be mated as the thread pitch stays in most cases the same. The difference in fact can be found in the thread form, Whitworth is 55 degrees and UNC is 60 degrees Quote Link to post Share on other sites
ianc Posted February 3, 2009 Report Share Posted February 3, 2009 My "Zeus Data Charts" from the late 1950s (when I was a student apprentice) show a difference between BSW and UNC. Although they might appear to "fit", the result will not have the strength of the correct item and you could cause damage to the tapped holes in the bell housing. Ian Cornish Quote Link to post Share on other sites
Alec Pringle Posted February 3, 2009 Report Share Posted February 3, 2009 (edited) Jean's comment is correct, thread angle is the the most obvious difference - although threads per inch are the same for most (not all) BSW and UNC corresponding sizes, the thread form is significantly different. Mixing the two will result in a substantial reduction in potential holding force, potential strength is even more reduced, and there is a likelihood of suffering serious fatigue . . . especially vibration induced fatigue. In other words, use the correct bolts !! Bear in mind also that UNC and BSW utilise different head sizes - if on dismantling you need to dig out a Whitworth spanner or socket to avoid rounding the bolt head, then almost certainly you're removing an incorrect BSW bolt and not a UNC item. Make sure you use correct replacements. My experience is that incorrect use of a BSW bolt where a UNC bolt was required is less damaging than the ramming of a UNC bolt into a BSW threaded hole . . . . Cheers, Alec Edited February 3, 2009 by Alec Pringle Quote Link to post Share on other sites
Tom Fremont Posted February 3, 2009 Report Share Posted February 3, 2009 To the foregoing excellent advice let me urge you to ensure you have the right bits to align the two when assembling. On later cars this was done with (2) 3/8" diameter bolts or dowels at 180 degrees, one of which is located just above the starter motor. Omitting this step will likely consign you to clutch actuation grief Quote Link to post Share on other sites
boggie Posted February 3, 2009 Author Report Share Posted February 3, 2009 Hi Ian, Engine to gearbox fixings are all studs, UNC into the block, a short length without thread and a UNF thread for a nut. Can't give you an exact length - just what you need, but not too long or you'll have trouble locating the gearbox back on the engine (assuming an in situ change - obviously no problem if both units are out of the car. AlanR Thanks All, Alan has it right, I have ordered the studs and nuts from the TR Shop. Cheers. Quote Link to post Share on other sites
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