[Geof]

I realised you missed out an important for the Brits among us.

British Association screw threads
From Wikipedia, the free encyclopedia

British Association or BA screw threads are a largely obsolete set of small screw threads, the largest being 0BA at 6 mm diameter. They were, and to some extent still are, used for miniature instruments and modelling.

They are unusual in that they were originally defined in terms of the imperial units then in use in the United Kingdom, but were deliberately set to be exact multiples of the metric system units, rounded to the nearest thousanth of an inch. This anticipated metrication by about a century.

The British Standards Institute recommended the use of BA sizes in place of the smaller BSW and BSF screws (those below 1/4"). Generally, the 0BA size was dropped in place of 1/4" BSF in assemblies that included larger fasteners, however, in smaller equipment that was primarily electronic/electrical the 0BA size would typically be used in place of the 1/4" BSF or BSW screw where it was the largest size required.

BA threads are still used in some precision instruments, such as optics and moving-coil meters, relays etc.

[lgalla]

Matthew
Thanks for mentioning Whitworth,I knew it existed but couldn't remember the name.I have asked at tool stores about a third older wrentch size and they did not know.I have an old 2 ton Wadkin table saw.For adjusment I use"the metric adjustable"but some bolts require a socket.Hopefully now I know the name I may find the right tool.Interestingly enough the allen bolts fit my keys.I also wonder how old this saw is.
Thanks
Larry

[mattinker]

Larry,

I doubt very much that you'd be able to find "Whitworth" wrenches in a hardware store. You might find them in a junk shop or a "car boot" sale, (I don't know the Canadian for this, brocante in French maybe you say garage sale?) I bought mine thirty five years ago when I finished training a a mechanic! Having lived in France for nearly thirty years, I couldn't say when they disappeared from UK hardware stores!

An amusing anecdote about Whitworth and BSF, the "wrench" size was based on the diameter of the thread and not the width accross the flats. Whitworth was a machinist! A 1/4" whit was also a 5/16"BSF, across the flats, it was a little bigger than 9/16"UN(commonly found on British car battery terminals!)! This system was subsequently changed during the first world war, to economise on steel, nut and bolt head sizes were reduced to the size below ie, 1/4"whit was used on a 5/16" thread diameter, 5/16"BSF was 3/8"! It's no wonder the "motor" industrie hastened to change all that!

If your stuck for a Whitworth nut stud or bolt, UNC is so close (60° as opposed to 55°) that they work very well!

Matthew.

[mattinker]

Eric,

here's question that I don't think was ever covered in my mechanics training, how do Whitworth/BSF Allen key sizes work? I have just started a CNC conversion on a 1944 Colchester lathe. I've been gayly using those "big black spanners" (smileing to myself as I work, the French don't understand UN threads, let alone Whitworth!) that I've been dragging around for the last thirty-five years! The gib screws on the cross slide are allen keyed! I have a set of metric and imperial Allen keys, so I think I'll be able to work on them, but what was the standard? I've done an extensive "google", but I haven't found anything!

Any ideas?

Matthew

[thkoutsidthebox]

I'd like to see a pic of one of those spanners if you get a chance to upload one, I'm not sure if the picture in my head is correct....and well.....its probably not! Thanks.

[mattinker]

thkoutsidthebox


To compare with your memory! 3/4" whitworth, 3/4 UN and a 3/8 whit, 5/16 BSF.

The really old ones like the 3/4 whit had a really bad shape that needed a lot of space and were a real pain! I still have quite a lot of sockets too!

Matthew

[Cruiser]

If your going to have a sticky dissertation on threads then it only makes cense to have an equal write-up attached to explain the dynamics of taps and dies that corelate to all the various sizes and classes of threads. This is where it really gets interesting. And can cost dearly when you use an incorrect tap to cut a thread when a classification is called out on the print !

[Cruiser]

Might as well include some basics on measuring threads too, how about three wire and two wire formula's ! Might as well include plug gauges too ! OH and don't leave out the calc for definition of root pitch. HUmm what did i leave out now . . . . . . . .

[lgalla]

4-whit its worth,
In the 7T'ys,I had a 72 Honda 750,metric.In these days a motor scotter came with a tool kit under the seat.Friends with BSA's and Norton commandos would borrow my underseat tool kit as the spanners fit better than their own.?????
Larry

[mattinker]

For what it's worth,

10mm = 3/8"
13mm = 1/2" (12,7mm)
14mm = 9/16"
19mm = 3/4"

Those are the ones that I use a lot, I can't remember the bigger ones off hand! The fit is good enough not to do damage.

Matthew

[widgitmaster]

THREAD FORM SYMBOLS

ACME 60° STUB 60° Stub thread form
ACME STUB Stub Acme thread form
ACME-C Acme thread - centralizing
ACME-G Acme thread, general purpose
ANPT Aeronautica National Form taper pipe thread
AWWA American Water Works Association
BA British Association Standard thread form
BSF British Standard Fine thread series
BSPP British Standard Pipe Parallel
BSPT British Standard Pipe Taper
BSW British Standard Whitworth
MM ISO Metric thread form
N BUTT American Buttress screw thread
NC American National Coarse thread series
NEF American National Extra-Fine thread series
NF American National Fine thread series
NGO American National gas outlet threads
NGT American National gas taper threads
NH American National hose & fire hose coupling
NM National Miniature thread series
NPS American Standard straight pipe thread
NPSC American Standard straight pipe thread in couplings
NPSF American Standard internal straight pipe thread (dryseal)
NPSH American Standard straight pipe thread for hose couplings & nipples
NPSI American Standard intermediate straight pipe thread (dryseal)
NPSL American Standard straight pipe thread for locknuts
NPSM American Standard straight pipe thread for mechanical joints
NPT American Standard taper pipe thread
NPTF Dryseal American Standard taper pipe thread
NPTR American Standard taper pipe thread for rail fittings
NS Special threads of American National Form
PTF Dryseal SAE Short Taper pipe thread
SGT Special Gas Taper thread form
SPL-PTF Dryseal Short Taper Pipe thread
STI Special Threads for Helical Coil Wire Screw Thread Inserts
UN Unfied and American thread series
UNC Unfied and American Coarse thread series
UNEF Unfied and American Extra-Fine thread series
UNF Unfied and American Fine thread series
UNIV Unified Miniature Thread Series
UNJ Unified Thread Series with Controlled Root Radius
UNJC Unified Coarse Thread Series with Controlled Root Radius
UNJF Unified Fine Thread Series with Controlled Root Radius
UNR Unified Constant Pitch thread series with Controlled Root Radius
UNRC Unified Coarse Thread Series with Controlled Root Radius
UNRF Unified Fine Thread Series with Controlled Root Radius
UNS Unfied and American threads of selected special diameters and pitches

[woffler]

need to ask this question can i run a stepper sys with acme screws. i am new to this and i am trying to convert my square coloum mill to cnc a little at atime if possable

[widgitmaster]

YES!

[rokag3]

need to ask this question can i run a stepper sys with acme screws. i am new to this and i am trying to convert my square coloum mill to cnc a little at atime if possable

yes but better do it slowly or with delrin and not too fast.
there is a splendid alternative to the ballscrew and the acme it is the "DIY roller screw" it work differently than the industrial roller screw (VERY expensive) there is no backslash and no backdrive
see
http://www.cnczone.com/forums/showth...3&goto=newpost

[robotek]

Hi good people.
I have tried to ask in other threads, but no one responds. May be it's me, asking a wrong questions in the wrong places. It' just the website's configuration bit of confusing to me...
The question was: How do I make my machine move along x-axis (the longest one)? I figured, that using a lead screw would be little dangerous and speed restricting because it's almost 10 feet long. And besides, the gantry is not a loop shape, so I have to use 2 screws? I was thinking of using a linear gears, but they are so expensive!!! And in my case 2 sets is required!
Is there any other way to get in moving?
Please, see pictures of my project in gallery.
Anyone can help me? Please?

[widgitmaster]

Try using one motor per side with a corrugated timing belt. keeping the belt stationary and looping it over a drive pulley.
It's like a rubber rack gear!

[robotek]

Try using one motor per side with a corrugated timing belt. keeping the belt stationary and looping it over a drive pulley.
It's like a rubber rack gear!

Thank you!!! Yeah, this is probably the way to go for me!!! Still got to figure out motor sizing.

[widgitmaster]

Check out this link

[toneV8]

Does someone have table for inch screw threads.

Like for metric screw threads:
M5 0,8 to use drill 4,2mm
M6 1 to use drill 5mm
M8 1,25 to use drill 6,7mmm

and many other

[widgitmaster]

Does someone have table for inch screw threads.

Like for metric screw threads:
M5 0,8 to use drill 4,2mm
M6 1 to use drill 5mm
M8 1,25 to use drill 6,7mmm

and many other

Try this link !
Eric