LG45 pivot pins

peter weir

7 January 2011 at 22:52 #47967

I bought rear spring front pivot pins(SSPX07) from the Club some while ago to replace worn ones on my 1935 LG45 DHC (very early 12008 and may have been a ‘parts bin’ car using some none standard bits) The old nuts don’t fit and I’m having difficulty in finding the threads size to fit. Pivot pin thread measures 0.623″ with 20tpi. 5/8″BSF are 14tpi and 5/8″UNF are 18tpi. (UNF thread with Whitworth/BSF hexagon heads were I understand popular with Lagonda.) The only other alternative would be a slightly undersize 16mm (0.6299″) with 1.25mm (0.0493″) pitch.Very close but I can’t locate any 16mm x 1.25mm nuts. Any ideas on alternative thread options or small quantity nut suppliers (2off nuts required)

DavidLG45

8 January 2011 at 09:38 #47968

Hi Peter,

Namrick (http://www.namrick.co.uk) sell BSF and UNF 5/8 inch nuts etc. You can order online.

David

peter weir

8 January 2011 at 14:43 #47969

Hi David
Thanks for your reply but neither 5/8″BSF or 5/8″UNF are the correct tpi for the pin. If I can’t find the correct thread I’ll take them out again and die them down to 1/2″UNF butit’s just odd to produce pins (without nuts) which don’t seem to be a standardised thread. Handy to know suppliers as living up in the North of Scotland has its supply problems.
Regards
Peter

DavidLG45

8 January 2011 at 15:48 #47970

Peter,

Sorry, misread your post. 20 tpi would be British Standard Cycle (BSC).
See thread chart: http://www.classicmotorcycles.org.uk/technical/technical_thread_size_chart.htm

http://www.stainlessmiddleton.co.uk do stainless cycle nuts but I assume you need slotted or castle nuts, which they don’t do.

I suppose if you had access to a milling machine you could slot plain nuts yourself.

David

peter weir

8 January 2011 at 22:46 #47973

Hi David
Had a look at the thread chart and it looks a firm favourite.
I’d looked in my Machinery’s Handbook (1934 – goes with the cars) but could find no reference to the cycle threads.
Checked the stainlessmiddleton web site and they have them in various thickness so I’ll check in the morning and get a couple ordered. Slotting no problem on my milling m/c.
Many thanks for your help.
Peter

Colin M34

9 January 2011 at 11:22 #47974

Hello Folks,

The Lagonda Company were very fond of using 20 TPI threads. Fortunately the ever-helpful Tracy Tools
(01803-328603) pride themselves in supplying taps and dies in all sorts of non-standard threads. They tell me they do a lot of business with bikers so understand cycle threads very well.

Colin M34

peter weir

16 January 2011 at 19:06 #47991

Hi Colin and David
The 5/8″ x 20tpi cycle thread nuts arrived next day, but I’ve still got problems. I tried fitting it today and it won’t go on even one thread and firms up. I checked the pitch to make sure they had sent the 20tpi and not the 26tpi but it is OK.
I’m just re-fitting the steering box and column and noticed the clamp bolt holding the column support to the bulkhead bracket is also 5/8″ x 20 tpi so I tried the new nuts onto the clamp bolt and they went on fine! The nut for the clamp bolt won’t go on the pivot pin which leads me to suspect that the pivot pin is not
cycle thread. It is certainly 5/8″ x 20tpi but could be the thread form is different.
Any idea who in the Club might hold the drawings/specifications for the various items the Club gets re-manufactured who might be able to confirm what the thread was supposed to be.
Regards Peter

DavidLG45

17 January 2011 at 11:05 #47992

Hi Peter,

That’s weird. As you say, someone in the club must know.

David

petemick

17 January 2011 at 16:26 #47995

The 20TPI cycle thread of 5/8 inch diameter bolt had a core dimension of .5719 perhaps your bolts have a slightly shallow thread depth and the nut is binding on the bottom of the thread. A similar problem could apply to a shallow thread on the nut but I doubt that.

Brian Savill

18 March 2011 at 18:38 #48125

Hi. Sorry this reply is a little late.
Drawing for SSPX07 states thread to be 5/8 20 T.P.I.

Regards,
Brian.

peter weir

31 March 2011 at 23:43 #48148

Thanks Brian. I purchased some 5/8″ x 20tpi cycle thread nuts but they don’t fit the pivot pins and I suspect it may be something to do with the thread form which can vary between vee,flat top and rounded and the angle between the threads which can vay between 55 and 60 degrees depending if they are whitworth or metric/american form or even 47.5 degrees for BA. I’ve purchased a 5/8″ x 20tpi cycle die and will die the pins down to hopefullt fit the nuts I’ve purchased – the only ones I could find. I’ve been a bit busy lately and haven’t managed to get under the car but I’m hoping it will resolve the problem.
Many thanks
Peter