unknown thread of this tap

[vic neweyParticipant @vicnewey60017]

Can anyone identify the fine thread on this tap, it's 5/8 X 56 NSVT

I can't find any ref to NSVT other than a medical condition

[vic neweyParticipant @vicnewey60017]

[Michael GilliganParticipant @michaelgilligan61133]

I wonder if perhaps it should read NSVF

… as in Very Fine

MichaelG.

.

Edit: __ “… the Unified series adopted by Great Britain and the United States during the war, and the corresponding American National Standard. NC and UNC mean coarse thread. NF and UNF mean fine thread. NS means special thread.“

Ref. __ https://www.newmantools.com/taps/taptech.htm

Edited By Michael Gilligan on 27/01/2022 16:58:01

[egaParticipant @ega]

Excellent idea to have the built-in pilot!

[SteviegtrParticipant @steviegtr]

Fine thread

Steve.

[Bill PhinnParticipant @billphinn90025]

You can get a die to match.

 

Edited By Bill Phinn on 27/01/2022 17:46:17

[vic neweyParticipant @vicnewey60017]

Thanks to all for your replies, it's definitely reads as NSVT but can't find a ref to it

[Tony Pratt 1Participant @tonypratt1]

NSVT is unlikely to be a typo but Iv'e never heard of it. What else is printed on the shank?

Tony

[old martParticipant @oldmart]

It could easily be a special made for a particular job. I have a box of specials at the museum, from the toolboxes left to the museum. If very unusual sizes were specified, a firm would add the tooling costs to the quote and a specialist would make it.

The NSVT may be a code for the job it was used on and nothing to do with threads.

 The threads on the tap look like a multi start on my screen, probably an optical illusion. I would 56tpi to look like rings turned. I turned a 40tpi on a 1.26" diameter today and I cannot detect any helix angle by eye.

Edited By old mart on 27/01/2022 20:35:53

[RobCoxParticipant @robcox]

A quick google search produced a US website selling 5/8-56 taps with a review stating "needed for gunsmithing", so maybe thats where this thread finds a use.

[stuart jones 2Participant @stuartjones2]

It might be for threading rifle bores looking at the long lead at the front maybe to fit a smaller bore possibility an airgun /rifle

[Anonymous]

Posted by stuart jones 2 on 27/01/2022 21:28:36:

It might be for threading rifle bores looking at the long lead at the front maybe to fit a smaller bore possibility an airgun /rifle

Don't think so it's a bit too fine., 5/8 is a common barrel size but powder burners usually use 5/8 x 24 TPI to secure them to the action, can't think of any common airguns with a screw in barrel.

[bernard towersParticipant @bernardtowers37738]

I’d have to go for Valve Thread.

[vic neweyParticipant @vicnewey60017]

Posted by Tony Pratt 1 on 27/01/2022 20:18:23:

NSVT is unlikely to be a typo but Iv'e never heard of it. What else is printed on the shank?

Tony

———————————————————

It also reads as HSS GT

DORMER ENGLAND

[Rick HannParticipant @rickhann79631]

Posted by Mick Berrisford on 27/01/2022 22:21:00:

Posted by stuart jones 2 on 27/01/2022 21:28:36:

It might be for threading rifle bores looking at the long lead at the front maybe to fit a smaller bore possibility an airgun /rifle

Don't think so it's a bit too fine., 5/8 is a common barrel size but powder burners usually use 5/8 x 24 TPI to secure them to the action, can't think of any common airguns with a screw in barrel.

Perhaps you are looking at the wrong end of the barrel. Could it possibly be used the thread the inside of a 20 Ga.shotgun to install removable chokes? Hust a thought. Rick

[SamsarandaParticipant @samsaranda]

12 gauge shotgun choke thread size is 13/16” x 32. Dave W

[Roderick JenkinsParticipant @roderickjenkins93242]

NSVT is a tank mounted soviet era machine gun…

[Tony Pratt 1Participant @tonypratt1]

Posted by Roderick Jenkins on 28/01/2022 21:41:09:

NSVT is a tank mounted soviet era machine gun…

Oh I can see why Dormer 'England' made taps for it.

Tony

[IgnatzParticipant @ignatz]

Just a thought….

Considering how fine the thread count is, I'm wondering if this wasn't a special tap for something in the camera/optical field.

[Adam MaraParticipant @adammara]

As an ironmonger in the sixties or seventies Draper were selling of mixed lots of 100 taps, ex WD and by UK and USA makers, my cousin and I bagged the best ones for ourselves, but there were some very odd sizes and threads in the assortments. I still have a few, a 1/2"and 3/4" still in use for my garden irrigation projects!

So there a possibilty It may be for a milatary purpose.

[SillyOldDufferModerator @sillyoldduffer]

The NS bit is easy enough: 'The NS series is a catch-all category for threads which have the American Standard form, but whose pitches are not in the National Coarse or National Fine series.'

Possibly VT indicates a particular purpose like 'Vacuum Tube', or it might just be a catalogue code. Or a property such as 'V-Thread', meaning the valley root is cut sharp rather than flat.

Fine threads imply strong joints or gas tight, or thin-walled. As NS suggests USA origin, but the tap is British, I think it was made for a UK organisation that imported a significant quantity of an American equipment and maintained it locally. Loads of possibilities – could be military, maritime, aviation, medical, chemical engineering, pressure vessel etc. Could be military except the absence of a broad arrow, pattern number or NATO Stock Number hints it's not.

Whatever it is, it's special.

Dave

[Tony Pratt 1Participant @tonypratt1]

Yes I'm thinking thin walled components, pipe or possibly optical?? Definitely special!

Tony

[Phil WhitleyParticipant @philwhitley94135]

Why not ask Dormer?

https://www.dormerpramet.com/en-gb/pages/default.aspx?country=gb

[vic neweyParticipant @vicnewey60017]

I asked Dormer and got a reply but they have no knowledge of the tap, as they have been taken over it's possible that info from the past has been lost.

 

However I posted it on a Facebook machine forum and got lots of replies, today someone has posted this photo of a throttlefree banjo fitting which has the letters NSVT so my tap must belong to something like that

Edited By vic newey on 31/01/2022 09:40:29

[Tony Pratt 1Participant @tonypratt1]

Interesting, I'm sure Dormer has been taken over many times since the tap was made but worth a try. BTW I now know what a 'throttle free banjo' is. The hunt continues.

Tony

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