Fixings - Metric vs Imperial

[Bob Culver]

Modern hardware has heads of reduced depth etc and looks wrong even if the thread is not. Reduces the case for original. For fastenings not normally disturbed such as mudguared mounts metric not unreasonable provided not a mixture. For some repairs the small nut dia of UNF/UNC can be convenient. Non BSF taps and dies can be very cheap and can afford to modify where convenient for special jobs..

[A G Wood]

"Some cars are very confusing. Years ago I was working on a friend's Triumph Vitesse 1600 and was very puzzle trying to rebuild the front suspension until I realised it was BSF.The rest of the car was Unified. I assumed the unit was just carried over from previous models."
Yes, also Hillman/Humber product with those unique self locking nuts on the just -under -3/8 UNF [11/32?] big end fasteners which  would catch out the unwary fitters of 3/8 UNF self locking nuts.
Much more recently, on another make who had an apparent love of a mix of 'standard' and 'foreign'  fasteners, the 'umbrella style' park brake had two 5/16 x 18 UNF nuts on its floor pan mount [captive bolts] , but the nut  at dashboard mount [captive bolt again] was M8 x 1.25. Booby trap waiting for the air wrench aficionados replacing a park brake cable.

My own vehicle, which although an Austin isn't a Seven:  I tend to follow Martins example,  BSF/BSW/ and slotted screw heads, not cross-head etc. when visible/critical unless there's no feasible alternative. UNF as second choice. Invisible woodwork I tend to use Robertson. I try to avoid stainless. Having worked through the UNF to Metric years, I do this for no particular reason other than I only want to need to use the one set of wrenches/sockets on it. I've found quite a bit of 1/4 UNF/M6x1  driven into 1/4 BSF threaded holes on it too.

[Derek Sheldon]

Not a problem with a Rosengart they are all metric ???.
As a few have mentioned previously, I use metric where there is likely to be no need to undo them out on the open road, wings etc. My Opal is constructed that way.

[Duncan Grimmond]

On my projects I use metric if everything is new. On the specials I stick to original types on mechanical parts and threaded inserts but metric on all new bits of bodywork and ancillaries. Seems to work for me..

[Malcolm Parker]

I always use slotted head screws on the Austins and the slots have to be in line!  On the Ulster and Pytchley, which are both specials, I have used metric fastenings everywhere except on the original Austin running gear. As for carrying extra tools, a couple of M4 and M6 spanners together with a small ratchet and socket set really don't take up much space.  I keep an old Thorntons Toffee Tin under the drivers seat, it measures about 6" x 4" x 2" and contains all the tools I need to carry out 90% of the maintenance on the Austins.  I also have a tool roll for the larger tools.

[Chris Garner]

My preference is for an old Britannia Jones Shoe Car Kit tin!

[Ivor Hawkins]

Hurrah for imperial, that’s what I say!

[Mike Costigan]

Didn't Morris use British standard heads on metric threads ?

Yes they did; that was a legacy from acquiring the Hotchkiss Engine Company, which was of French origin. Prior to using the Hotchkiss design, the early Bullnose with the American Continental engine used a bewildering mixture of BSF, Whitworth, Metric and American Fine threads.

Similarly Georges Roesch used metric fittings with imperial heads on his Talbots.

[Stuart Joseph]

Good morning. It is often overlooked that the Zenith 26VA carb fitted to A7s has metric fittings whereas the similiar carb fitted to Fords are imperial - hence the number of damaged float chambers where the 7mm thread has been ruined by a 5/16th bolt.

Regards from the creative county - Staffordshire

Stuart

[David.H]

And 7mm helicoils are readily available! Great improvement on that anxious tightening into old Zenith Mazak!
7mm stilll used in the French (of course!) car industry, not so much (if at all) by the Teutons.