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5BA Threads

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Howard Lewis28/09/2020 18:27:11
3601 forum posts
2 photos

The chances are that the 5BA screws are undersize by a couple of thou because they have been truncated to avoid interference between toot and crests.

Most fasteners are made in this way, for just that reason.

Somewhere I still have the Apprentice Training handout giving the formulae to truncate UNF threads..

Howard

norm norton28/09/2020 18:34:14
134 forum posts
7 photos

What people are failing to acknowledge is that the BA range of sizes, especially in 4-14BA, and based upon metric principles, is vastly better than the Metric system has contrived to offer.

Tongue in cheek but I mean it

Norm

Michael Gilligan28/09/2020 20:36:23
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16342 forum posts
712 photos
Posted by norm norton on 28/09/2020 18:34:14:

.

What people are failing to acknowledge is ...

.

So presumably I am not included in ‘people’ angel

MichaelG.

norm norton29/09/2020 09:19:49
134 forum posts
7 photos
Posted by Michael Gilligan on 28/09/2020 20:36:23:
So presumably I am not included in ‘people’ angel

My apologies, you are very 'people' (and emoticon saintly)

At least you gave a sensible response to the OP and discussed his subject. Having re-read the thread I don't know why I thought my BA vs. metric statement was in any way appropriate; oh well, apologise rather than delete blush

Mike Donnerstag29/09/2020 09:38:21
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191 forum posts
40 photos

Michael Gilligan: I haven't used Elcoda, though I do use Paulus Bowparts who are also in Germany. Although they don't make the BA thread bow screws (reduced to 3mm) as used by the Hills workshop, they do the '3mm Inch Thread' bow screws, which are a reduced 5-40 UNC thread, as in the photo below:

inch thread screws (paulus).jpg

I have made these screws myself using a 5-40 die, closed down to give a nominal diameter of 3mm. However, like the 5BA bow screws, it seems I will need to make a custom tap in order to tap the thread on the brass eyelets.

I assume I will need to use silver steel, hardened and tempered. However, it's a very small tap and I'm wondering whether there is a way of holding it in a mill vice in order to mill the 'teeth'. Prior to milling I will need to turn a taper, as it will be a taper tap for through threads. I've never done any of this before, and would appreciate any advice anyone can give. I have ER40 collet blocks and a full set of collets which, although large, may help?? Even better may be holding the straight shaft of my ER20 collet chuck in the ER40 collet block, which may give more clearance for the milling bit. Does anyone have a process for making their own accurate taps at this scale?

Many thanks,
Mike

Old Crock29/09/2020 16:44:54
30 forum posts
18 photos

If you go to www.itemsmailorderascrews.com and click on an email link you'll get an extensive list of BA screws etc. They advertise in Model Engineer.

They list socket head countersunk screws in all sizes from 0BA to 6BA plus 8BA.

For example 5BA x 1/2" are £4.68 for 10, and sorry Martin 6BA x 5/16" are only £2.49 for 10. Other lengths are available!

I have not bought from them yet so cannot comment on availability or delivery but worth a try?

Michael Gilligan29/09/2020 17:15:09
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16342 forum posts
712 photos
Posted by norm norton on 29/09/2020 09:19:49:

.

Very noble of you, Norm yes

MichaelG.

Michael Gilligan29/09/2020 17:33:19
avatar
16342 forum posts
712 photos
Posted by Mike Donnerstag on 29/09/2020 09:38:21:

Michael Gilligan: I haven't used Elcoda, though I do use Paulus Bowparts who are also in Germany. Although they don't make the BA thread bow screws (reduced to 3mm) as used by the Hills workshop, they do the '3mm Inch Thread' bow screws, which are a reduced 5-40 UNC thread, as in the photo below:

[…]

I have made these screws myself using a 5-40 die, closed down to give a nominal diameter of 3mm. However, like the 5BA bow screws, it seems I will need to make a custom tap in order to tap the thread on the brass eyelets.

 

.

Thanks for the additional information, Mike

You obviously know your subject much better than I ever will ... but I am still a little bewildered.

Are these threads really produced with a closed-down 5-40 die, or are they perhaps a truncated thread-form ?
.

If you have a commercially produced one available, I would be happy to photograph it for our mutual education.

MichaelG.

.

Edit: The two lines for 5-40 on this chart make interesting reading

https://www.engineersedge.com/screw_threads_chart.htm

Edited By Michael Gilligan on 29/09/2020 17:41:01

Rod Renshaw02/10/2020 17:07:33
169 forum posts

Thanks to everyone who contributed links to suppliers and thread tables to this forum thread, I now know of sources of supply I was unaware of.

Rod

Martin Kyte02/10/2020 18:43:13
avatar
2048 forum posts
36 photos
Posted by Old Crock on 29/09/2020 16:44:54:

If you go to www.itemsmailorderascrews.com and click on an email link you'll get an extensive list of BA screws etc. They advertise in Model Engineer.

They list socket head countersunk screws in all sizes from 0BA to 6BA plus 8BA.

For example 5BA x 1/2" are £4.68 for 10, and sorry Martin 6BA x 5/16" are only £2.49 for 10. Other lengths are available!

I have not bought from them yet so cannot comment on availability or delivery but worth a try?

Ah well, it's good to see things are still available. I'm still happy to have my stock even if I have to write them down in value on the asset register. (as if)!!

I shall have to check to see if I've got anything elese that is more obscure. What treasures does anyone else possess

regards Martin

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