5BA Threads

[Mike DonnerstagParticipant @mikedonnerstag]

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.

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 CrockParticipant @oldcrock]

If you go to http://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 GilliganParticipant @michaelgilligan61133]

Posted by norm norton on 29/09/2020 09:19:49:

.

Very noble of you, Norm

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

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 RenshawParticipant @rodrenshaw28584]

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 KyteParticipant @martinkyte99762]

Posted by Old Crock on 29/09/2020 16:44:54:

If you go to http://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

[Author]

Posts