Morris Minor Owners Club

Declan
As regards the Damper filler plug. I can confirm the following:-

It is 5/16" O.D.

It has 26 TPI.

Holding a 26 TPI cycle thread tap against the threads of the filler plug - the form of both the cycle thread tap and the filler plug appear to be of a similar profile but not a perfect match.

Holding a 26 TPI BSB tap against the threads of the filler plug the form of both the BSB thread tap and the filler plug are a perfect match.
Screwing a 26 TPI BSB die down the threads of the filler plug the dies fits perfectly with no resistance or removal of metal.

Unfortunately I do not have a 5/16" x 26 TPI cycle thread die to screw down the filler plug threads.

http://motalia.com/Html/Charts/cycle_chart.html
Phil

Thanks Phil!
Mystery solved
5/16" x 26 TPI BSB.

Regards
Declan

The two holes at the O/S front of a late 940 cylinder head and which are just below the thermostat housing and usually support an alternator or air pump are 8mm x 1.25.

Richard
One more for the list. Glovebox hinge securing screws on my MM - 2 BA x 3/8 inch long hex. head. Spanner size 8 mm. or 5/16".
Bob

It seems the thread for the reproduction SII boot badge screws are not 2BA, in fact they are larger than 4BA. Anybody know what they are?

For a start - what outside diameter are they?

M4 just about fits - so I'm going to say 3BA or a UNF alternative?

Have found these charts very useful during my rebuild, but I cannot see details of the correct size/thread of the steering column pinch bolt?
A previous owner has used a metric bolt and locking nut, and want to use original please. I guess its 3/16 BSF ?

The original fastening for the clamp that secures the column to the steering rack pinion is a 1/4" x 1 1/8" BSF bolt (bolt -using the BMC Pts List name/definition) (Pt No: AJD6111Z) with a spring washer under the plain nut.
Some parts lists give the length of the bolt as 1 3/8".
A fastening that is threaded all down its length is not suitable for this application as any movement of the fastener threads can wear the steering rack pinion and column clamp.

I have replaced the fastening in my steering column to steering rack clamp with a 1/4" x 1 1/4" UNF high tensile (grade 10.0) Allen headed bolt with a plain washer under the bolt head and a washer under the nylock nut.

Moss supply an alternative UNF bolt (Pt No: GHF200) to the same dimensions.

Thanks Phil. I'll order the Moss one as suggested.

I cannot see details of the correct size/thread of the steering column pinch bolt?

The original fastening for the clamp that secures the column to the steering rack pinion is a 1/4" x 1 1/8" BSF bolt

Thanks Phil, the list has been updated.

Below right is the original 1/4" BSF steering clamp bolt from my Minor 1000 and left the replacement UNF Allen headed bolt.

Hi All,

Can anybody confirm the standard thread size for the lower trunnions (both clock-wise and anti-clockwise). I am assuming these are a BSF thread, but cannot find a specification anywhere.

I need a suitable die to confirm whether my king pin or new (!!) lower trunnion is at fault. I am suspecting the trunnion....

Thanks
Michael

All I can confirm is that the threads used on the swivel pin (not king pin) & trunnions are not BSF.
The specification of the threads is and has been the bane of Morris Minor owners for many years.
BMC used to supply a undersize die and oversize trunnions so as the prolong the life of the swivel pin/trunnion threads.
I suspect that the threads used on original & replacement swivels are lathe turned and not die formed.
I have never seen dies available for cleaning or checking threads other than the BMC undersize dies.
As a rule if the swivel threads have a pointed or sharp peak they are worn. Good swivel threads have a flat peak.
A photo of the swivel pin threads posted on here would be helpful in gauging an opinion as the their serviceability.
If the trunnion is able to rock on the swivel threads the swivel and trunnions are worn.
Phil

Thanks Phil

philthehill wrote: ↑Wed May 09, 2018 5:50 pm The specification of the threads is and has been the bane of Morris Minor owners for many years.

Boy did I learnt that today!

I took the legs to my local friendly engineering workshop. They measured all 4 threads on both legs (only one was suspect) and confirmed the original thread as 0.725 in (which is a little over 23/32" - 23.2 to be precise) and 11 tpi (a very unusual tooth count). They were unable to identify the thread, but were confident that although it is a trapezoid (ie 'flat') thread, it is not an ACME standard. In his words "It's a real oddball!"

We ran an 11 tpi through it, which tidied it up nicely. The trunnion now spins on cleanly without any play. Success!

Michael

All,
Diff drain/filler plug size please? My drain plug thread is damaged so I can only screw the plug in about half way resulting in a small leak. I assume that running the correct size tap through and flushing any swarf out with some oil will solve the problem?
Thanks
John

The drain/filler plug has a taper thread so will not go fully into the axle thread.

OK, thanks, so how do I clean the thread? What size tapered tap do I need? Or do I get a spare drain plug and file some vertical grooves in it and try and clean it out using the drain plug as a sort of tap? How was/is it done in manufacturing? Which is the harder metal, the diff case or an ESM drain plug? I don't want to have to buy a new diff assembly, the oil leak is much cheaper!!!!
Thanks
John

The thread in the diff casing is a parallel thread, so you could run a 1/2" BSPP tap through it, but if the tapered plug already goes in up to about halfway, that is actually what it should do.

The plug can be sealed with some PTFE tape wrapped around the plug threads, before screwing it into the casing, which should seal it completely.

Richard,
Many thanks for the information, I had a look at the drain plug yesterday as it is probably ony screwed in about one third of the way, it didn't appear to be leaking as much but will get a tap and clean up the threads.
John