jerrytr5 Posted July 27, 2015 Report Share Posted July 27, 2015 Is anyone else getting a tad peeved with the number of new pattern parts turning up with Metric threads? I can understand track rod ends perhaps with Metric nuts, but I just tried to fit some engine mounts and not only were these fitted with oversize studs (M10 not 3/8) but they were fitted with different size nuts (16 & 17mm a/f) and to add insult, were not parallel. Clearly they will go back. I'm just going to have to remember to ask "is it fitted with Metric threads" every time I purchase anything. I can see why, when you see the price of UNF against Metric, but it's getting pretty annoying especially when faced with trying to find the right nut to fit a stud when it could be any of three thread pitches in some cases (1.00 / 1.25 / 1.5) for the same o/d. Right, now I've got that off my chest, where to get some proper TR5/6 engine mounts? Jerry Quote Link to post Share on other sites
Jersey Royal Posted July 27, 2015 Report Share Posted July 27, 2015 Hi Jerry, Get hold of Ntc and you will be very suprised that quite a few standard fittings were metric. He will be able to help you out. Cheers GUY Quote Link to post Share on other sites
stuart Posted July 28, 2015 Report Share Posted July 28, 2015 Worst one I`ve had lately was master cylinder/slave clevis forks with metric threads. Smart lad wanted! Stuart. Quote Link to post Share on other sites
Peter Cobbold Posted July 28, 2015 Report Share Posted July 28, 2015 A friend who collected vintage parts was delighted to find an affordable Flying Lady radiator mascot. She had pride of place in his museum. Until he decided to mount it using the thread at its base. Yes...metric thread. Peter Quote Link to post Share on other sites
AlanG Posted July 28, 2015 Report Share Posted July 28, 2015 My niggle lately was TR4A rocker arms with metric threads. Alan. Quote Link to post Share on other sites
Marc R Posted July 28, 2015 Report Share Posted July 28, 2015 Arrg… on my side based in France, I am hunting to withdraw any metrics threads on my Triumph TR6 & Stag :-) and … they may come back through UK suppliers... :_( Regards Quote Link to post Share on other sites
Lebro Posted July 29, 2015 Report Share Posted July 29, 2015 I have found one use for metric threads, 3/16" or 2BA threads are used in a number of places eg fixing boot budget locks, spare wheel cover locks etc. when these wear out, a usefull fix is to run an M5 tap through (same TPI near as damm it) & then use Stainless metric screws. Similar for the even smaller threads used to fasten the escutchions to these locks, these seem to be 4BA, & can be tapped M4 (again very close tpi). Of course I would always use the correct imperial thread if possible, but needs must sometimes ! Bob. Quote Link to post Share on other sites
Dave Larnder Posted July 29, 2015 Report Share Posted July 29, 2015 Hi Metric Nuts What is the thread on the holding down screws at the back of the Speedo and Rev. Counter? It´s not 2BA which is too small and No.12 UNF it ain´t and Bob,it ain´t M5 either. Dave Quote Link to post Share on other sites
Lebro Posted July 29, 2015 Report Share Posted July 29, 2015 I have a spare speedo, & some thread gauges, so I will find out & report back. Bob. Quote Link to post Share on other sites
RogerH Posted July 29, 2015 Report Share Posted July 29, 2015 Hi Dave, it's old and it's a gauge = 4BA (but I bet it isn't) Roger Quote Link to post Share on other sites
stuart Posted July 29, 2015 Report Share Posted July 29, 2015 It may well be ME (Model engineers) or BSC (British Standard Cycle) Stuart. Quote Link to post Share on other sites
Lebro Posted July 29, 2015 Report Share Posted July 29, 2015 (edited) It comes out as 34 TPI, at 4.9mm (0.192") dia I cannot find any thread which fits this ! (model engineers, or Cycle dont do 34 TPI) The nearest match seems to be 3BA at 34.79 TPI, 4.1mm Dia If you cannot get nuts to fit I would run a 3/16" BSF die down at 32 TPI, 4.7mm dia or a 10-32 UNF at 32 TPI, & 4.8mm dia. Bob Edited July 29, 2015 by Lebro Quote Link to post Share on other sites
AlanG Posted July 29, 2015 Report Share Posted July 29, 2015 Can't be that much of a weird thread as the new knurled nuts you buy screw on ok. Alan. Quote Link to post Share on other sites
RobH Posted July 29, 2015 Report Share Posted July 29, 2015 The only thing from my ancient Engineers Reference Book which is close to your measurements Bob is a pre-ISO French Standard thread - 0.75 mm pitch (33.87 tpi) and 5mm OD with 60 degree thread form. Quote Link to post Share on other sites
Dave Larnder Posted July 30, 2015 Report Share Posted July 30, 2015 Hi Guys 4BA and 3BA are already smaller than 2 BA which I said was too small as is no.12 UNF. and as I said to BOB it ain´t metric. I do have some M.E. dies so I can try them but no cycle threads. I do have some smaller knurled nuts that look the same type, so maybe there were smaller holding down bolts on other instruments, but not on my two. The mystery continues. Dave Quote Link to post Share on other sites
Lebro Posted July 30, 2015 Report Share Posted July 30, 2015 The thread I checked was on a TR3 speedo Bob. Quote Link to post Share on other sites
AlanT Posted July 30, 2015 Report Share Posted July 30, 2015 M4.5 Quote Link to post Share on other sites
RogerH Posted July 30, 2015 Report Share Posted July 30, 2015 Hi Folks, it is a 3BA thread pitch (34..84TPI) - I compared it to a NOS 3BA tap The diameter on my rev counter is apprx 0.15675" which is a little smaller than the classic 3BA 0.1614 not not enough to say that it is not 3BA. Good old fashion thread design - in fact one would say the 'perfect' thread design. Roger Quote Link to post Share on other sites
Lebro Posted July 30, 2015 Report Share Posted July 30, 2015 Humm that suggest there is more than one size of these going around, mine was definately 0.192 Dia. I used a vernier set to ½", & counted the threads from one end to t'other. Did it several times, & got exacly 17 each time. Could not use thread gauge as it did not have a 34 TPI blade. Bob. Quote Link to post Share on other sites
RogerH Posted July 30, 2015 Report Share Posted July 30, 2015 (edited) Hi Bob, I have found a thread that is 0.196 x 32TPI it is referred to as a 'GAS (brass pipe) thread' But then a 10/32 UNF would be similar - but that is actually 0.190" dia. However it wouldn't work with your 34TPI !!! Roger Edited July 30, 2015 by RogerH Quote Link to post Share on other sites
graeme Posted July 30, 2015 Report Share Posted July 30, 2015 (edited) From my research there are at least three different sizes of knurled nuts for Smiths/Jaeger type instruments, one of which is 3BA, one metric, 4.5? as Alan T states and the third thread is probably 8-32 UNF but not confirmed. Cheers Graeme Edited July 30, 2015 by graeme Quote Link to post Share on other sites
Lebro Posted July 31, 2015 Report Share Posted July 31, 2015 M4.5 would be the nearest to what I have then at 33.8 TPI & 0.177" Bob. Quote Link to post Share on other sites
AlanT Posted August 1, 2015 Report Share Posted August 1, 2015 I am quite surprised this isn't 32 TPI. This is common in both US and British thread standards. When you measure TPI with a caliper it's the fence-post versus fence-panels problem. There is one more crest/valley than turns. Quote Link to post Share on other sites
Lebro Posted August 1, 2015 Report Share Posted August 1, 2015 Alan. I know about that, It is definately 34 TPI +/- a small fraction of a thread ! I have thread gauges, the 32 was too coarse, there was no 34 gauge in the set 'cos nobody uses 34 TPI ! Quote Link to post Share on other sites
RogerH Posted August 1, 2015 Report Share Posted August 1, 2015 The measured thread is 0.196 diameter. The original nominal size may be slightly bigger. There is a thead (21 S&H) that is nominally 0.202 diameter with 32.6tpi. This is not spot on but getting awfully close. S&H = Siemens & Halske I have a very comprehensive thread chart (hundreds of the devils) and there are NONE at 34tpi. Roger Quote Link to post Share on other sites
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