Thread size Odd ball-ium

[Traffer]

I guess there is always something new to learn.
I have learned a lot buying odd ball stuff on eBay for super cheap.
Did it again.
This is it.....
1/8-40 thread grub screws.
I had never heard of such a thing. I thought "it must be a typo or Chinese to English confusion". So I figured "it's gotta be actually 8-40 threads like the standard scope mount screws we are all familiar with. Around a buck for a package of 20 screws so I pop for it...Turns out they ACTUALLY ARE 1/8-40 screws. Are you kidding me? Spent a half hour trying to research such an odd ball size. NOTHING. So I go back to eBay and look for more screws, taps and such (now I need a 1/8-40 tap)
Turns out for you folks "across the pond" who are laughing now...It is BRITISH STANDARD THREADS.
I don't know if they use it much anymore, but, sure enough there it is.
NOW, because of the price of this stuff... Less than $2.00 for a tap (I ordered 3 of em) and a little over a dime a piece for all kinds of various length cap screws...I am now a happy user of BRITISH STANDARD THREAD SIZE 1/8-40.
By the way it is just a tiny bit bigger than 6-40 which is actually a nice fit for a lot of stuff that I do. But I pity the person who tries to work on the stuff I make with these....I might have to include a note on everything warning them of this ODDBALLIUM.

[Winger Ed.]

I had fits with nuts & bolts when I had a Triumph and MG.

Bolts looked the same as American ones, but the shape of the threads were different. Rounded instead of a sharp 'V'.

Sometimes it took a 'extension' on a ratchet handle to snug 'em up.

[Gewehr-Guy]

Also known as British Standard Whitworth, or B.S.W.

[Traffer]

Also known as British Standard Whitworth, or B.S.W.

Oh, I have heard of Whitworth... Lot's of old tooling is in that standard. Didn't know the full name was British Standard Whitworth. Must be the standard before they went to metric.
Thanks for that.

[LAGS]

I had similar issues with bolt sizing when I restored a 56 BSA motorcycle back in the 70s.
Wanted to keep it stock , so a three month project ended up taking a year.

[shaune509]

Machinery's handbook is your friend. Lists most threads used in the past 100+ years in US types, British, European and Metric. Many odd pitch sizes that were used in old guns and machines before WW2 [proprietary] that are one side +/- of standard NC/NF. Like 1/4-18 or 1/4-32
Shaune509

[John Taylor]

1/8-40 is a standard size, sometimes it is listed as a machine screw size 5-40. I have taps with these markings. First time I saw this size was for axles on slot cars over 50 years ago.

[john.k]

1/8 x40 was a very common thread in electrical appliances in the days when they actually had sheet metal frames and chassis...1/8 Whit.Also used in at least one military gun Im aware of...British car and bike electrics used the BA threads,which are actually metric in origin......British bikes used many 26tpi based threads,BSC and many specials....Pre 67 Jap metric threads can also be different to standard metrics.

[samari46]

And to add to the list of British threads is the model engineering threads which I believe were all 40 threads to the inch. Used to have a bunch of British model making magazines.Steam engines both stationary and fully operable steam locomotives,steam powered boats both small and large. And my personal favorite was the flash steam model boats. Frank

[merlin101]

I still have some old Whitworth wrenches in my tool box, my favorite is the 1/2 Whit.

[GONRA]

GONRA sez watchout for 55 degree thread form. Not the 60 degree we are all used to!!!
From Memory: Luger pistol Barrel barrel threads are 55 degree Whitworth - 20 / inch.

[indian joe]

GONRA sez watchout for 55 degree thread form. Not the 60 degree we are all used to!!!
From Memory: Luger pistol Barrel barrel threads are 55 degree Whitworth - 20 / inch.

On machinery you will get away with the 55 vs 60 degree but its easy to get used to the idea that Whitworth is the same TPI as National coarse - they are - all except for the most popular size (half inch) where whitworth is 12TPI and NC is 13TPI ---- so with a good fitting spanner and a long handle you will get it almost a nut depth before something is boogered -spare a thought for Aussies - we got the lot to deal with - BSW/SAE/NF/NC/Metric- then a kids bike was all 26TPI no matter the diameter along with a lot of early pommy motors and such - IH tractors from the 1980's had National fine /coarse threads on the motor and transmission and metric for the running gear and body work. Tis what we get when Bureaucrats start to mess with things.

[Traffer]

It took a little shaking for things to settle out to Unified Thread Standard and Metric. Some folks want to get rid of Unified thread standard and just have metric.
To that I say N O W A Y. People are lazy and stupid enough nowadays. Those different standards keep a person on their toes.

[Petrol & Powder]

I still have some old Whitworth wrenches in my tool box, my favorite is the 1/2 Whit.

I see what you did there :groner:

[Petrol & Powder]

I don't mind vehicles with English fasteners or metric ones, it is when they mix them up on the same vehicle that I get a bit perturbed.

Speaking of mildly perturbed, (that's the British equivalent of enraged here in America) you haven't learned to cuss until you work on an old British car with rusted Whitworth fasteners that aren't quite Whitworth dimensions anymore, steel that is somehow capable of being thick & heavy but still weak and rust prone (I'm not sure how the Brits figured out that metallurgic combination) and Lucas electrics.

[John Taylor]

I understand they drink their beer worm over there, seems Lucas made refrigerators also.

[Traffer]

I see what you did there :groner:

Thanks, It went right over my head...now I see the light.

[Traffer]

I understand they drink their beer worm over there, seems Lucas made refrigerators also.

What is a Beer Worm? I'm not drinking any Brit beer NOW.

[Bad Ass Wallace]

Had troubles with another British thread " Enfield Inch". My lathe cuts 36,38,40 tpi but this thread was 37TPI

I managed to get a thread die from a little shop in England and now turn the body in the lathe and thread with the die.

[Daver7]

seems Lucas made refrigerators also.
Lucas is the Prince of Darkness

[Petrol & Powder]

Lucas is the Prince of Darkness

The Lucas motto: Get home before dark

[BigEyeBob]

Model enginreers thread comes in 32tpi and 40tpi .I use it fairly often for fine adjustment thread spindles and the like .The thread in an English made micrometer is 40tpi .IIRC Parke Hale had thier own thread for thier cleaning rods and jags 37 1/2 threads per inch , they refused to change to the standard that the other companies used on thier rods and jags ,needless to say that PH products are not that popular these days.

Then there is the BA thread series.

[NoZombies]

I understand they drink their beer worm over there, seems Lucas made refrigerators also.

In the 70's they tried branching out and made a vacuum cleaner as well. Only thing Lucas ever made that didn't suck.

[uscra112]

I once counted six different thread standards on one brand new 1967 BSA. Or maybe it was seven.

[big bore 99]

As a retired tool and die maker,45yrs., I did a lot of prototypes many for the welding industries. You can do almost an unlimited combination of diameters and threads per inch.

[Petrol & Powder]

..........You can do almost an unlimited combination of diameters and threads per inch.

And the British have proven this,... repeatedly :bigsmyl2:

[Herb in Pa]

Then there's the classic British car smell.....leather and burnt wiring...……..

[indian joe]

Some of the stupid english ideas had a reason behind them
When I was a kid our vehicle registration had a very hefty engine tax component that was figured by multiplying cylinder bore diameter x number of cylinders - that kept english makers (even jaguar) locked into smaller bore longer stroke motor design way past the time they knew better - a short stroke yankee engine of similar displacement could cost near twice as much to register -
none of which explains why they put these machines together inside out and back to front
old mechanic mate of mine (long gone) used to say it wasnt the foxes and rabbits the poms sent to Australia to annoy us - no mate it was austins and bedfords!

[Pressman]

Ask any P-51 engine mechanic about the trials of bolts and fasteners on the RR Merlin engines, and the way the English manuals were written explaining what fastener and wrench size to use.
It's no wonder Packard got involved in the manufacture of the engine and made it work.