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unknown thread of this tap

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vic newey27/01/2022 16:50:16
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148 forum posts
77 photos

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 frownthread.jpg

Michael Gilligan27/01/2022 16:52:48
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20108 forum posts
1043 photos

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

ega27/01/2022 16:56:02
2500 forum posts
200 photos

Excellent idea to have the built-in pilot!

Steviegtr27/01/2022 17:15:04
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2422 forum posts
336 photos

Fine thread

Steve.

Bill Phinn27/01/2022 17:45:14
739 forum posts
103 photos

You can get a die to match.

 

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

vic newey27/01/2022 20:14:25
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148 forum posts
77 photos

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

Tony Pratt 127/01/2022 20:18:23
1934 forum posts
12 photos

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

Tony

old mart27/01/2022 20:30:59
3724 forum posts
233 photos

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

RobCox27/01/2022 20:39:29
59 forum posts
20 photos

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 227/01/2022 21:28:36
13 forum posts

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

Bezzer27/01/2022 22:21:00
157 forum posts
13 photos
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 towers27/01/2022 22:38:09
578 forum posts
109 photos

I’d have to go for Valve Thread.

vic newey27/01/2022 22:40:52
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148 forum posts
77 photos
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 Hann28/01/2022 19:18:02
13 forum posts
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

Samsaranda28/01/2022 20:51:09
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1408 forum posts
5 photos

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

Roderick Jenkins28/01/2022 21:41:09
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2176 forum posts
608 photos

NSVT is a tank mounted soviet era machine gun...

Tony Pratt 129/01/2022 09:03:13
1934 forum posts
12 photos
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.surprise

Tony

Ignatz29/01/2022 10:22:44
avatar
168 forum posts
100 photos

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 Mara29/01/2022 11:10:24
167 forum posts
3 photos

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.

SillyOldDuffer29/01/2022 12:19:06
Moderator
8513 forum posts
1914 photos

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

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