Thread: Bolt sizes and dimensions

Originally Posted by Ozdunc

Ive been searching like crazy and I've gathered that there are many different standards when it come to nuts and bolts.
BSW, BSF, BSC, UNC, UNF, BA and that BSW is pretty much UNC, and BSF is the same dia as UNF but a different thread pitch, and BA is for small bolts under 1/4" or 6mm.
But what I can't find is what is used on which landrover and where.
Are there standard sizes for a 2a I should think of buying just to have hanging around ? I've got a few bolts missing from my floor panels for example.

Cheers

The body bolts on IIAs are mainly UNF - in fact most are 1/4" UNF. BS and UNC are used on some drivetrain parts.

Usually though after dismantling landies you end up with a surplus of bolts. IME the original bolts are quite good quality so I usually reuse them if not rusty.

You will find EVERYTHING! Including metric!!

UNF, UNC (ie Whitworth except 1/2inch) & BSF are "stock" but over the years, who knows what prev owners have added. I, for one, freely admit to using M6 & M8 nuts & bolts for 1/4 & 5/16ths UNF purely because I can't get the latter in Gal. They look better & don't rust.

I urge you to buy a digital vernier to measure bolt diameters accurately- ~$25. Then get a wall chart for threads and a thread guage.

1. Measure the diameter in mm.
2. Look at the chart to find the closest imperial diameter.
3. Count the TPI (turns per inch) with your thread guage.

Do this & you will not damage any thread where it matters (eg hubs etc) by buying the wrong bolts or nuts.

vernier and dont forget a goos set of thread form gauges....

a thread file for the more common sizes is always handy too.

'cues my ignorance but what's a thread form gauge, is it different a standard thread gauge?
and a thread file? A super small file or is it a special tool? Do you need different sizes for different threads?

Originally Posted by Ozdunc

'cues my ignorance but what's a thread form gauge, is it different a standard thread gauge?
and a thread file? A super small file or is it a special tool? Do you need different sizes for different threads?

They are correctly called a screw pitch gauge. They look like little feeler gauges with saw teeth. You will need them in UN, BS, & Metric. Get one of those cheap plastic vernier calipers. They read in fractions. Drill gauge plates are good for this also. What is your e-mail address. I will send you some thread charts.

UN is a 60 degree thread form. BS is 55 degrees. Metric is 60 degrees. BA is 47 1/2 degrees. BA is found on instruments and electrical fittings. 0BA is the largest size. It is near identical to M6 x 1.0.

BA & BS are obsolete systems whose use was supposed to be discontinued after unification of thread systems with the USA in 1950. Hence we have the UNC, UNF, UNEF, UNS systems etc. Yanks rarely use the U. They didn't unify with anyone. UK & Canada unified with them.

Thread files are used to clean damaged threads. You need a file with a different part for each pitch. Better to use dies or die nuts(hexagonal rethreading dies) to restore damaged threads. A die can cut a new thread. A die nut generally can not except in soft stuff like brass or plastic.

If buying new taps and dies buy high speed steel rather than carbon or chrome tungsten steel. Carbon/ct steels are OK for easy material like mild steel, brass, soft aluminium. For stainless, tool steels, heat treated aluminiums, titanium and other difficult material you need HSS.

Commercial bolts are made slightly undersize. Get yourself a bucket of bolts, screw pitch gauges, and thread charts and sit down and teach yourself to identify threads and become familiar with the slight undersize.

Do not mix and match threads of differing angles. This causes crushing of the thread crests, and the fastener is often then blessed with self-loosening and an inability to maintain correct torque.

A couple of additions to the above. I can't think of any places where UNC is used But I am sure they exist!) but BSW is used. And although BSW and UNC have the same thread pitch for most sizes, BSW has a 55° thread angle and UNC has 60°, so that using one with the other qualifies you to wear a striped apron.

Not mentioned above is BA, which is used in Series Landrovers mainly for electrical and instrument fittings.

Series 1 was built entirely using BSF, BSW and BA, but started using unified threads with the diesel engine (and possibly earlier on some other bits) with the change to unified threads still not quite complete at the end of Series 3 production, by which time the change to metric threads was under way.

And you always have to bear in mind that bits can replaced with either earlier or later or even foreign parts, and this applies particularly to standard bits such as bolts and nuts.

John

Originally Posted by JDNSW

A couple of additions to the above. I can't think of any places where UNC is used But I am sure they exist!) but BSW is used. And although BSW and UNC have the same thread pitch for most sizes, BSW has a 55° thread angle and UNC has 60°, so that using one with the other qualifies you to wear a striped apron.

Not mentioned above is BA, which is used in Series Landrovers mainly for electrical and instrument fittings.

Series 1 was built entirely using BSF, BSW and BA, but started using unified threads with the diesel engine (and possibly earlier on some other bits) with the change to unified threads still not quite complete at the end of Series 3 production, by which time the change to metric threads was under way.

And you always have to bear in mind that bits can replaced with either earlier or later or even foreign parts, and this applies particularly to standard bits such as bolts and nuts.

John

UNC is what replaced BSW around the world over the last 60 years. I can assure you it is in common use. The only new items and new fasteners using BSW are mostly old designs still being made in places like India and China.

Almost no high grade (equivalent SAE 5 or 8) BSW or BSF fasteners are still made. Just about any shop selling them are selling from very old stock. Some hardware stores are still selling BSW fasteners but these are very low grade general use items usually from Taiwan and inaccurately made..

I mentioned BA in line 3 of the above post. Found in very small screws on instrument and electrical fittings and small controls. LH & RH BA turnbuckle rods were used on Merlin engines on various control rods. Only place I have ever seen LH BA. Bruce Gardner, B.S.F. Bolts, Melbourne has BA fasteners and taps and dies including left hand.