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Tap and Die

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Peter Love 129/03/2019 08:53:29
17 forum posts
3 photos

Hi all I have a Jones iambic Morse paddle in my collection, it was manufactured in the USA until 1998, the screw threads are 3/16" NF 50 (very fine) I am unable to track down a tap and die of that size, does anyone know were I might find a set, I would even consider a complete set that contains this size if there was no other alternative.

Peter Love ( Amateur Radio call G0KOK )

JasonB29/03/2019 09:16:23
17830 forum posts
1950 photos
1 articles

An American thread of 3/16" nominal size would tend to use a number as just about all their threads under 1/4" do in this case a #10 would be correct.

Are you sure it is 50tpi and there is a #10-48 UNS or the finer #10-56 UNS both of which you can buy taps for.


Edited By JasonB on 29/03/2019 09:21:43

Rik Shaw29/03/2019 09:38:20
1313 forum posts
352 photos

I have drawn a blank on that size - perhaps it is a special. These people will make specials in 24 hours but I suspect the price will make your eyes water.



Nicholas Farr29/03/2019 09:57:48
2208 forum posts
1063 photos

Hi Peter, as Jason has pointed out, the NF, NC, UNF and UNC don't do a standard for under 1/4", you can get Unified screw threads under 1/4" for attachment purposes and ANC/ANF but these are gauge sizes and none of them match what you want. If it is 3/16 x 50 T.P.I. then it is quite likely to be a special fine pitch, which would be made to order. Warrior used to do such taps but not die's (I don't know if they still do though). I guess the male thread would have been machine cut.

Regards Nick.

SillyOldDuffer29/03/2019 10:05:38
5614 forum posts
1154 photos

Agree, triple check the size. I can't find anything in 50tpi.

NF was made obsolete in 1949 but it is interchangeable with UNF, dimensions here.

If it is a standard size, not 3/16" x 50, Tracy Tools are a good source and they might be worth asking. They do have 3/16" x 60tpi.

However, 3/16" x 50tpi is suspiciously close to Metric M5 fine, which would probably fit:

  • 3/16" = 4.8mm
  • 50.8tpi = 0.5pitch

It is possible that a US maker might have used a metric thread. Or, they're a bunch of sods who used a non-standard thread to guarantee parts sales!


PS Can you post a photo of your Iambic Paddle please?  Morse keys have a fan-base! 

Edited By SillyOldDuffer on 29/03/2019 10:09:25

Nicholas Farr29/03/2019 10:26:41
2208 forum posts
1063 photos
Posted by SillyOldDuffer on 29/03/2019 10:05:38:

Agree, triple check the size. I can't find anything in 50tpi.

NF was made obsolete in 1949 but it is interchangeable with UNF, dimensions here.


Hi Dave, with the exception of I" NF/UNF.  1" NF 14 T.P.I.  1" UNF 12 T.P.I. and don't ask how I found out.

Regards Nick.

Edited By Nicholas Farr on 29/03/2019 10:28:42

Brian G29/03/2019 10:35:19
671 forum posts
26 photos

There is a 3/16 x 50 die on eBay right now, unfortunately the seller doesn't state the profile LINK


mark costello 129/03/2019 18:23:40
583 forum posts
12 photos

Victor Machinery in the States are known for sourcing odd ball taps and dies, if a last resort.

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