Cutting male threads

[DismalduncParticipant @dismaldunc]

Help! what size do I turn to?

[DismalduncParticipant @dismaldunc]

Hi there, a dopey question from a complete Noob, I have zeus tables that show tapping drill sizes and clearance hole sizes, but what size do I need to turn a bar down to in order to thread it with a die? think I can guess that for M10 it will be 10mm (but not sure !)  but what about BA threads?  if you can help with this one I would appriciate it as I’m fairly sure that I’ve worn google out with combinations of this question

[Les Jones 1Participant @lesjones1]

Hi ???,

               You are correct that a 10 mm thread will be cut on a 10 mm bar.

Here is a link to BA thread dimensions.

 http://en.wikipedia.org/wiki/British_Association_screw_threads

I Googled “ba thread dimensions” to get this.

Les.

 

[DismalduncParticipant @dismaldunc]

Hi Les, Thanks for the infoand clearing that up for me, I wasn’t sure if I used the “outer diameter” or not, I was unsure if the die simply cut metal away or kind of pushed some of it up! (sounds REALLY daft when I write it down)  Thanks again Dunc

[Eric CoxParticipant @ericcox50497]

No, it’s not at all daft. The dies we use cut into the metal and form the thread by removing material. Thread rolling uses a hardened die which is pushed into the metal and the thread profile is transfered onto the work piece. It means there are no sharp edges on the thread at the peak or the trough and less chance of stress points being created thus leading to a stronger thread.

[chris stephensParticipant @chrisstephens63393]

Hi Duncan,

Before the days of Wikipedia it was fairly difficult to find the dimensions, Zeus and the Reeves equivalent were not much help, unless you just wanted to tap a hole. I f you are getting serious about engineering, try to locate a copy of “Machinery’s Handbook” it is a fountain of knowledge of nearly all things mechanical. Don’t be put off by the fact that it is American, some good things come from there, it covers British stuff too.

On the BA thread front I got so fed up with the lack of dimensions in a handy form, that I made my own appendix to the ZEUS book, which had ALL the dimensions and in both imperial and metric units.

The moral for a “NOOB” here is  just because you can’t get something you want, make it yourself. There are a lot of useful gadgets and gizmos out there that no one makes, so remedy the situation for yourself. If you think something might work or would be handy, within the bounds of safe practice, give it a go, you will learn something from both success and failure. The FIRST  “E” in SMEE is for Experimental.

Here endeth the philosophy class.

chris stephens

PS Quite often when using a die to cut a thread, there is a raised burr formed which gives the impression that the stock has grown, a fine file or appropriate abrasive will soon clean this back to size.

[James BParticipant @jamesb]

Hi Duncan,

 

Also as a relative newcomer, I purchased a copy of ‘The Model Engineers Handbook’ by Tubal Cain – this is a lot cheaper than Machinerys Handbook, and has loads of useful stuff in there that is appropriate for our hobby – thread information, tool cutting angles, cutting speeds & feeds, heat treatments, etc, etc.

 

Only problem is trying to keep it clean in the workshop!!

 

James

Edited By James Burden on 13/11/2009 14:00:27

[chris stephensParticipant @chrisstephens63393]

Hi James,

Well if you want to be cheapskate about it

I bought my copy for less than the cost of Tubal Cain’s but that is by the by. Yes, TC’s book is a must have for Model Engineers, but don’t be fooled too much about tool cutting angles, as any Diamond tool holder owner will tell you. One size fits all (nearly)!

Can’t immediately find my copy of TC’s book, but I seem to recall it is a bit brief on some details of BA threads. Could be wrong, so don’t quote me.

The other newer alternative is Harold Hall’s book “Metalworker’s Data Book” No. 42 in the WPS collection. This lists most details of BA threads and has IMP equivalents for some details, but not tapping drill (number) sizes. If you haven’t bought your copy yet, I am sure they will have plenty at MEX at Sandown, you are going, of course, aren’t you?

chris stephens

[James BParticipant @jamesb]

Already have my day pass approved by SWMBO!

[chris stephensParticipant @chrisstephens63393]

Signed in triplicate and witnessed?

[BazParticipant @baz89810]

Regarding books on thread data Machinerys Handbook published a book solely on screw threads, about 290 pages worth. My copy is edition twenty with a price label for £1.95 and was published in 1972. It appears to cover a lot more threads and in greater detail than the traditional Machinerys Handbook

[chris stephensParticipant @chrisstephens63393]

Hi Baz,

I must look out for a copy, but the internet is still a useful resource.

Even with the most comprehensive thread listing, you will still come across some oddity. Recently i was asked to make a plug for the oil ways on a pre-war Lancia engine, it did not conform to any “standard” size old or new. Must have been an in-house size, still, a lathe and a (very) little brain power solved the problem.

chris stephens

[Peter G. ShawParticipant @peterg-shaw75338]

re Tubal Cain’s model Engineers Handbook & thread data.

 

There is a useful book by Tubal Cain in the Workshop Practice Series. No. 12, Drills Taps & Dies which covers a lot of useful stuff about threading.

 

Regards,

 

Peter G. Shaw

[BazParticipant @baz89810]

Hi Chris,

regarding your Lancia thread, it is still common practice in industry to b***tardize a thread either by an odd diameter or an odd pitch. I work in the aerospace industry and our products have “home made” thread sizes so our competitors parts will not fit. I agree totally about the internet as a resource but I still like an old fashioned book to read in bed when I cannot sleep. 

[John Stevenson 1Participant @johnstevenson1]

Posted by chris stephens on 13/11/2009 13:14:24:
Hi Duncan,

Before the days of Wikipedia it was fairly difficult to find the dimensions, Zeus and the Reeves equivalent were not much help, unless you just wanted to tap a hole. I f you are getting serious about engineering, try to locate a copy of “Machinery’s Handbook” it is a fountain of knowledge of nearly all things mechanical. Don’t be put off by the fact that it is American, some good things come from there, it covers British stuff too.

On the BA thread front I got so fed up with the lack of dimensions in a handy form, that I made my own appendix to the ZEUS book, which had ALL the dimensions and in both imperial and metric units.

 

The early Zeus books had a better layour as regards BA sizes but they got chopped when they put the Metric fine in.

 

A far better pocket book is one called Engineers Reference Data Charts available from Cromwell tools for about £3, like a Zeus book but waxy paper not laminated so won’t last as well but it has twice the content and full tables including BA.

Well worth getting a couple of copies, one for the house and one for the shed.

 

I bought 4, desk, workshop, upstairs bog and downstairs bog.

 

John S.

 

[chris stephensParticipant @chrisstephens63393]

Hi John,

Thanks for the tip, will look out for one, or two.

By “downstairs bog” would that be the same as the “downstairs reading room”

chris stephens

[chris stephensParticipant @chrisstephens63393]

Hi Baz,

Quite understand why you would make special bits, to confuse the opposition, but hardly worth it for a roughly 14mm dia. plug.

Absolutely agree about hard copies, but reading in bed is a no-no fall asleep too easily, refer to above post about “reading room”!

chris stephens

[mgjParticipant @mgj]

Osborne do a wonderful freebie wallchart. Covers all the common threads. Only got one – in the workshop.

 

Not BA though! Nor ME.

 

Blackgates catalogue for all the ME threads – photocopy the back page.

 

Also lists the tapping size for a 75% engagement which is the norm I believe.

 

If one wants a good reference, Ian Bradleys the Myford Handbook lists ME, whit, BSF, gas , BA, all the letter and number drills etc in an annex at the back.

[Vapeur89Participant @vapeur89]

Take a look at  http://www.gewinde-normen.de/en/index.html

Almost all existing thread past and present 

[DismalduncParticipant @dismaldunc]

Well chaps thanks for all the help! it looks like I’m gonna need an extra shelf in the loo , spent yesterday machining the standard for my stuart 10v and today am wearing my smug hat as it all went ok , so thanks again and I will try not to fill the forum with all my dafty questions Dunc

[CirclipParticipant @circlip]

DON’T belittle yerself Dunc, you’ll get about a dozen answers and then you can pick which works for YOU.

 

   Many roads to Rome an all that.

 

  Regards  Ian.

[chris stephensParticipant @chrisstephens63393]

Hi Duncan,

Congrats.on your success.

More daft questions please, gives us itchy typing fingered folks the chance to exercise our index fingers.

I agree with Circlip, (yes it can happen,) As they said on TV last week, “the M1 the M40, the M5 and the M6 all go to Birmingham, which route you take depends on from where you start.”

chriStephens

[KWILParticipant @kwil]

For a useful workshop list, go to Myford’s stand at Sandown and buy yourself a Laminated Chart, which shows all the common thread data, tapping and clearance holes with the centyre part of the chart taken up with, imperial/metric drill and dimensional equivalents. If you want the set over depths for screw cutting you need to look further.

[BERT ASHTONParticipant @bertashton57372]

 

One thing that model engineers enjoy is a bargain, and you can’t get a better

bargain than free, I refer to the MODEL ENGINEERS COMPANION, a free

software program distributed by the Gravesend Model Marine and Engineering

Society.   http://www.gmmes.co.uk 

I have this program on my computer desktop and find it very handy when planning

projects, for quick reference to imperial / metric conversions, thread, drill, sheet/wire and nuts and bolts.

Please download it and give it a try and if you don’t like it you can always delete it. 

Bert Ashton.

[Author]

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