[Healeys] What Thread?

Sun Dec 20 16:15:19 MST 2020

I can’t speak to the thread as I have never checked it and don’t have access to it to check right now, but I do know that nut on the adjusting end of the generator bracket is one of the few nuts on my BT7 where only a “whitworth” wrench will properly fit, so at I am sure that at least the “nut end” of the part will be BSF threads.

I agree with others that when working on Brit stuff from before the mid 60s, and for bikes before the 70s, having thread gauges (imperial, BA and metric) on hand, and a table showing all the tpi for the various threading systems is essential to understanding the occasional odd-ball fastener that gets thrown at us.    If you think early Healeys are bad, you should try the motorcycles.  Both BSA and Velocette ( the makes I am somewhat familiar with) not only made some of their own threads which are unique, but used weird thread systems such as “Admiralty Fine thread”, in addition to BSF, BSW, BA, BSP and BSPP!  For laughs, the fasteners on the M.G. XPAG engine all have whitworth heads, but metric threads, as it was based on a French Hotchkiss motor that M.G. had acquired, but they made the heads all whitworth so British mechanics would not all have to buy new sets of spanners!  That threw me for a while after buying my first old M.G.  I attached an article that provides some explanation of thread types FYI.

Cheers, Mirek

From: Healeys <healeys-bounces at autox.team.net> On Behalf Of john harper
Sent: December 20, 2020 5:19 PM
To: Harold Manifold <manifold at telus.net>
Cc: Healeys <healeys at autox.team.net>
Subject: Re: [Healeys] What Thread?

Harold

I believe that you will find that both should be BSF

On Sun, 20 Dec 2020 at 17:48, Harold Manifold <manifold at telus.net <mailto:manifold at telus.net> > wrote:

Michael,

After learning from several of my mistakes when I mismatched fasteners on my 1960 BT7 I always measure twice and assemble once. I have an original of the part in the picture. The big end is 20 TPI with a major diameter that matches a 7/16 UNF. A 7/16 - 20 UNF nut fits. The small end is 24 TPI and the closest major diameter would be a 3/8 UNF but the diameter is undersized however a 3/8 - 24 UNF nut does fit.

To help identify the tread type I measure the TPI and the major diameter and the go to this website to see what fits. Knowing the tread pitch helps to narrow down the possibilities.

https://www.ring-plug-thread-gages.com/ti-thread-data-charts.html

I trust this helps.... Harold

  _____  

From: Healeys [mailto:healeys-bounces at autox.team.net <mailto:healeys-bounces at autox.team.net> ] On Behalf Of Kees Oudesluijs
Sent: Sunday, December 20, 2020 2:50 AM
To: healeys at autox.team.net <mailto:healeys at autox.team.net> 
Subject: Re: [Healeys] What Thread?

If UNF7/16 is just to large it may be metric, probably M10. In that case the stud's outside diameter should be just shy of 10,0mm or at most 10,0mm when it is shoddily cut.

Kees Oudesluijs

Op 20-12-2020 om 11:12 schreef john harper:

Mike 

Both treads should be BSF. The problem is that not enough attention is given to detail. Suppliers cannot bother to get things correct but they know they have used an incorrect thread or otherwise, they would not have supplied the nuts. The treads are most likely metric.

Rgds

On Sun, 20 Dec 2020 at 09:19, Michael MacLean <rrengineer.mike at att.net <mailto:rrengineer.mike at att.net> > wrote:

The threaded pillar in the picture was purchased from Ahead4Healeys.  This is the pillar for the generator adjusting bracket.  It came without the nuts needed for the ends.  I can't figure out what type of threads these are.  I bought a 1/2" BSF nut and a 7/16 BSF nut for it.  Problem is both of those nuts are too loose.  When I try to tighten the large thread on the front engine plate it will not tighten up.  It gets almost tight then pops loose and spins.  The threads on the pillar are not damaged, so it must be the wrong nut.  Same for the other end.  A UNF nut will not go more than a couple of turns then stops.  I even tried running a metric die over the threads and no dice.  I am confused. 

Mike MacLean 

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