Nut & Bolt Sizes.

[Rik ShawParticipant @rikshaw]

I use a mixture of all sorts to suit whatever fixings come to hand. Here are two thread types I don't think have been mentioned.

The two on the left are marked VT (Vermont Tool & Die), ¼” x 48 HS NS M2I .

The one on the right is marked SOSSNER (Sossner Tap & Die Corp.) ¼” x 40 NS.

NS would be “National Special” right?

Rik

Edited By Rik Shaw on 13/03/2017 16:49:36

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Rik Shaw on 13/03/2017 16:45:54:

NS would be “National Special” right?

.

Not exactly … [more like National Superseded] 

**LINK**

http://www.ring-plug-thread-gages.com/ti-N-vs-UN.htm

MichaelG.

.

Edit: Smiley added for Jason

… The linked page is seriously worth a look though.

Edited By Michael Gilligan on 13/03/2017 17:51:34

[JasonBModerator @jasonb]

I'd say you still have special, be it an old NS or a newer ref UNS these are threads that fall outside UNC, UNF and UNEF. (Coarse, fine & extra fine)

Plus at the time they were likely made the S would have stood for special.

This is the table I tend to use that shows your 1/4 x 48 under UNS (special)

Edited By JasonB on 13/03/2017 17:43:54

[Rik ShawParticipant @rikshaw]

"more like National Superseded"

I feel a bit like that myself Michael these days. Seriously though, I have just used the 1/4" x 40 to tap the steam manifold on a new boiler but I might have balked had I read your link first. The thread standards people must have their heads completely screwed – perhaps a spinal tap might help them?

Rik

[JasonBModerator @jasonb]

Be careful Rik.

1×4 x 40 UNS and 1/4 x 40 ME are not teh same thread angle. You may get away with it you may not. If you have the matching UNS die then use that for the parts that will screw into the hole but if you are buying commercial fittings these will have the 55degree ME form not the 60degree UNS form

[Rik ShawParticipant @rikshaw]

Thanks for that Jason but I have a 40 NS die to go with the tap and I will be making my own pipe fittings to suit from brass. These will be a lot easier to machine than the manifold (and the steam chest and cylinders) which I have made in aluminium bronze. Cor, that is some tough old stuff – but why? Because I had some the right size.

Rik

[Willliam PowellParticipant @willliampowell36769]

NS is a U.S. 60 degree National Standard

UNC is unified national coarse

UNF is nified national fine

UNEF is unified national extra fine

All of these have been hashed out by the US SAE and ASME to sort out the limits and standards

[Harry WilkesParticipant @harrywilkes58467]

Posted by John Flack on 13/03/2017 10:27:48:

Checking on a link, we seemed to be overwhelmed for choice. Generally the choice is made for us by those who make whatever eqpt we use. When a bespoke is desired is there a specific criteria to be observed?. I simply look at what is to hand and think "that seems about right" and proceed from there. Assuming(?) fasteners are made to equal tolerances would a fine thread be preferable or non preferred to a coarse thread for general fastening use? If so why?

Chart sizes indicate that 20BA nuts are possible. Has any living soul ever seen a nut of this size, and where can I get some?

​John 10 & 12BA are the smallest I use and those can be challenging and I would not want any thing smaller!

H

[John FlackParticipant @johnflack59079]

Harry W

I regularly use/did use bolts down to 16 BA mainly to replicate bolt detail on patterns for components in gauges 0 – 3

Have a set of "box spanners " made by pressing a range of nuts into the end grain of small balsa section

Asking a question which won't concern the majority, has the specification for 14 BA been changed this century as taps supplied to me no longer fit my elderly stock of nuts.

[Martin KyteParticipant @martinkyte99762]

Don't forget the old BSL series

Martin

[John FlackParticipant @johnflack59079]

Adverting to MKs original question and his use of thread gauges, are such gauges designed to measure female threads? The ones I own a chunky penknife type design have a blade about 10 MM deep. OK perhaps for traction engines etc, but far to wide for my miniature needs. I have assumed that they are fof measuring male threads. How

do you measure female threads smaller than the depth of the gauge blade, is there an answer??

[Michael GilliganParticipant @michaelgilligan61133]

Posted by John Flack on 15/03/2017 14:11:27:

How do you measure female threads smaller than the depth of the gauge blade, is there an answer??

.

With a Go/NoGo gauge or [more common approximate substitute] a good quality male screw … Unbrako capheads are usually good enough.

MichaelG.

[BazyleParticipant @bazyle]

You screw a bit of wood or plastic into the hole, unscrew and hold up against the gauge, with an eyeglass for the smaller ones. Once you have an idea you can confirm with a test screw if you have one. Can still be caught out by the difference between Whitworth and UNC flank angles causing a screw to bind after a few turns in the same way as a slightly wrong tpi would so you have to think a bit about the age and origins of the item

[Phil BoylandParticipant @philboyland37326]

This standardisation to a Metric collection does get me thinking maybe I should do it for new tasks, would make life so much easier. Luckily I don't have too many unknown sizes so wouldnt take too long to size and sort incase I do need them for something or other.

[Howard LewisParticipant @howardlewis46836]

If you have a selection of known sizes /threads, (one of each) they can be used as rough and ready thread gauges. But beware of mixing Unified and Whitworth form threads. They may be the same pitch (tpi) but the different thread form will cause jamming. BA has a lot of commonality with Metric, but again, the thread form is quite different.

As a desperate measure, check using a tap or a Die, but be VERY careful, if it starts to cut, STOP, it isn't what you thought, (unless its been damaged)

Once you have sorted out your hardware, store in labelled containers, (as a minimum "Whit"," BSF", "BA", "UNF", "UNC", "Metric", etc). Even better if you can store as individual sizes.

Be aware that the hexagon sizes for Whitworth form threads were reduced, to save material, during WW2.

So that the prewar BSF hexagon size became the postwar BSW.

And you will come across oddball fixings and/or mixed hardware on machinery.

On the Bristol RE bus/coach, (Standardised on Unified fixings) the bolts holding the clutch pressure plate to the flywheel had A/F heads, but were BSF threads to suit the Gardner engine which still used Whit form.

C A V DPA fuel pump parts were dimensioned in Metric, but were Unified form, (UNF and UNEF) initially being a Hartford Machine Screw design produced under licence. C A V had started as Bosch licencees, so standardised drawings on metric dimensions.

At one time, prewar Morris cars, used engines made on the continent, with metric fixings, whilst the chassis used Whit form fixings.

Leylands changed from Whit form to Unified, so that the Leopard chassis used Unified fixings, but the 0600 or 0680 engines, being an older design, were to Whit form standard for fixings. The engine was mounted to the Unified standard chassis by mounting brackets using Whit form hardware. When the 500 Series engine (A new design to metric standards) was introduced, no doubt it would have been possible to find all three thread forms on one vehicle!

Possibly, the same situation existed when A E C introduced their metric standard V8 into existing lorry chassis.

So my advice is to check before using, and if it seems sticky or tight, don't force it, the threads are probably not the same.

Howard

[Ian S CParticipant @iansc]

If you happen to have a DH 82A Tiger Moth, or some similar aircraft with a DH Gipsy Major, you will find the engine has metric fittings, while the airframe has BSF and BA threads.

Ian S C

[John FlackParticipant @johnflack59079]

Howard L gives solid advice in his post avoiding nugatory tarradiddle BUT as fasteners can be brass, steel, high tensile, half nuts aero nuts etc etc this raises the question should an amateur even consider reusing any fastener of unknown origin? The experienced can make an informed choice, much will depend on the use to which it is to be put.

As an amateur who has rebuilt motor vehicle engines, certain fasteners that I would classify as "stressed" would be replaced with known quality replacements. I would never re use a nylon/aero type nut. Just my personal logic with no science to back it up. The old items being junked to avoid mishaps.

[Nigel McBurney 1Participant @nigelmcburney1]

I was asked to make a fuel jet for a old David Brown tractor carburettor ,probably a petrol paraffin tractor.knowing that some carbs had French origins,I careful checked the old jet,and the carb body as to was die cast and any error on my part may damage the thread in the old and frail die casting,it was as I suspected French metric not ISO the difference is .05 of a mm in pitch on a m4 thread,not much but enough to wreck the die cast thread.the customer was more than happy with jet and a couple spares,he had to bear the cost of a new tap and die but did not care and told me to keep them. I had learnt about 50 years ago that metric pitches can vary, from an engineer i worked under at the time so I went and bought a machinery's screw thread handbook which has proved to be so useful.

[John FlackParticipant @johnflack59079]

Ah French fine thread. Important if you own a MG TD TF 1500. As Michael Caine said " not………………………………….!

[vintagengineerParticipant @vintagengineer]

Bugatti uesd all odd number metric threads and Austin used Admiralty Fine threads right up to the very last Mini Metros!

[Richard S2Participant @richards2]

Posted by John Flack on 13/03/2017 10:27:48:

Chart sizes indicate that 20BA nuts are possible. Has any living soul ever seen a nut of this size, and where can I get some?

Smallest A/F steel Nuts/Bolts for me so far are the ones I made. 0.0669" (1.69mm) A/F from my Commercial Hex Steel Rod stock, shown here in the middle-

The other 12BA (lower) items are commercially made.

The top 14BA items are also commercially made.

I could only find 16BA (brass) nuts listed in my 30 year old price list from Clerkenwell Screws Ltd .Smallest Steel was 14BA.

My reference book extracts state that BA sizes from #17- 25 are generally unavailable, having been replaced by Watch, or Horological thread forms (not sure when).

Regards

[Author]

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