Author Topic: 10-40 UNS ? UNF ?  (Read 582 times)

Offline fumopuc

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10-40 UNS ? UNF ?
« on: February 14, 2020, 09:00:13 AM »
Dear Lady and Gentlemen,
as an European metric guy, I am bit confused in this above mentioned  thread matter. 
American rim fire spark plugs are available with a 10-40 thread.
All the documentation I can find, is a definition of 10-40 UNS https://www.gewinde-normen.de/uns-gewinde.html
Together with some 10-40 plugs, I have bought a also a 10-40 tap at S/S ignition.
This tap is marked with 10-40 UNF (S). I can not find any documentation about 10-40 UNF or UNEF.
Looking at e-bay, there are some Chinese shops offering a set of tap and die.
In the picture for the offer, the tap is marked with 10-40 UNF above this with (S) same as Roy sells, the die is marked with 10-40 UNS.
May be someone of the imperial world can lead me out of this jungle.


Kind Regards
Achim

Online Jo

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Re: 10-40 UNS ? UNF ?
« Reply #1 on: February 14, 2020, 10:28:03 AM »
Standard American threads are either Unified Coarse ( UNC ) or Unified Fine ( UNF ). Your link is to another series of threads they have called Special Unified Thread Series.

If you look at the sizes they offer various pitches at each size... this is somewhat similar to what here in the UK we do with our Model Engineering threads where you can get for each imperioulous size either 26 TPI, 32 TPI or 40 TPI  ;)

I suspect that the "specials" will overlap with standard UNF from time to time, you may have one of them.

Jo
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Offline Jasonb

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Re: 10-40 UNS ? UNF ?
« Reply #2 on: February 14, 2020, 01:43:49 PM »
Specials don't overlap as they will not be special if they did. They are generally a non standard pitch for a given diameter that falls outside the common UNF and UNC range.

Glow plug threads and miniature spark plugs are another example that use 1/4 x 32UNEF  (extra fine) This would be a bit like using a metric M6 x 0.5 which is neither metric coarse or metrc fine

I find this chart quite helpful when building the American casting kits as it shows the regular UNC and UNF pitches as well as the UNEF and UNS

https://www.sizes.com/tools/thread_american.htm

Online steamer

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Re: 10-40 UNS ? UNF ?
« Reply #3 on: February 14, 2020, 01:58:18 PM »
All good points....and one last thing

Be careful with Chinese taps at least in 40 thread group.   I have a few and they don't match their associated dies well at all.  Most of the time, you can size a die to match the tap by adjustment, but a few of mine I've given up on and single point the male threads to match the tap.

S&S makes nice stuff, I'd stick with them, but I would still try the fit on a scrap piece before I committed to the actual part.

Dave
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Online Mcgyver

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Re: 10-40 UNS ? UNF ?
« Reply #4 on: February 14, 2020, 02:03:37 PM »
Here we're kind of half and half, metric and imperial. The UN or course refers to the thread profile, and you know what the diameter and tpi are.   While the character after the UN defines the series, afaik its just a way to create common sets of thread pitches for all the obvious reasons.  If you tell me its UN 1/4 20, I don't need to know thats UNC, as I already know the form, diameter and pitch. 

UNEF is iirc extra fine and S is special - whatever you want it to be.  Its extremely rare to encounter anything but UNF or UNC, but, if presented with a UN"x" I wouldn't much care what the x stood for, so long as I had the diameter and tpi.
« Last Edit: February 14, 2020, 02:07:30 PM by Mcgyver »

Offline fumopuc

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Re: 10-40 UNS ? UNF ?
« Reply #5 on: February 14, 2020, 06:35:12 PM »
Jo, Gents, thanks for all the comments and explanation.


So it seems to be as already assumed.
The one and only 10-40 is a so called UNS thread.
So the marking of the Chinese manufacturer is not correct. May be Roy from S&S will have a similar source. 


Dave, I have had already the same idea to check the tool first in a sample piece of steel, before I will try to do the thread in my BME cylinders.
Thanks for the reminder.


Kind Regards
Achim

Online steamer

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Re: 10-40 UNS ? UNF ?
« Reply #6 on: February 14, 2020, 06:47:19 PM »
I think our Stevehuck can provide good quality taps.as.well

Dave
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Online Dave Otto

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Re: 10-40 UNS ? UNF ?
« Reply #7 on: February 14, 2020, 06:55:57 PM »
Hi Achim

Morrison and Marvin also have the taps.

http://sparkplugs.morrisonandmarvin.com/taps.php

Dave
« Last Edit: February 14, 2020, 07:05:57 PM by Dave Otto »

Online Jo

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Re: 10-40 UNS ? UNF ?
« Reply #8 on: February 14, 2020, 08:02:02 PM »
Looking at the size would a 3/16" x 40 work, EKP stock carbon ones: https://www.ebay.co.uk/i/331113826193

Rotagrip have HSS ones: https://www.ebay.co.uk/itm/3-16-x-40-ME-Model-Engineer-HSS-Tap/362070375358

Jo
« Last Edit: February 14, 2020, 08:06:39 PM by Jo »
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Offline Don1966

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Re: 10-40 UNS ? UNF ?
« Reply #9 on: February 14, 2020, 08:05:39 PM »
I seen some taps listed as UNFS which is fine tread (start) tap.



Don

Offline Jasonb

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« Last Edit: February 15, 2020, 07:46:01 AM by Jasonb »