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Williams aperture thread size? I need help.


JiminPGH
(@jiminpgh)
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I am attempting to find/build/fabricate/cobble an extension to move my aperture closer to my eye, by about 3/4 - 1".

I believe I have determined that Williams uses a 7/32X40 thread size. Can anyone help me to figure out what that means is Std screw sizes? There are tons of hollow male-female stand-offs on Amazon that look like just the ticket, but I can't find the right thread size.

If there's an easier way to move a Williams aperture back, I'm all ears. The sight base is as far back as it can go. It works fine with a larger aperture, but I want to use the 1" disk with the tiny hole and rubber eye cup, and that requires near zero eye relief. (I guess I'm trying to build my own 10M match sight.)


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David Karch
(@david-karch)
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Anytime I’m looking for special hardware, I go to a real hardware store. Not a “big box” store. If you have an Ace Tru-Value or any old hardware store in your area, start there. May have to take the whole assembly to the store with you. 


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marflow
(@marflow)
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Champion's Choice (champchoice.com)

with that you can use these 

Gehmann Rear Sight Anti-Glare Tube (creedmoorsports.com)

and a European rear Iris 

so it not free to buy all the parts 

your other option is make the adapter yourself and that is going to take some R&D the 7/32 tape and dies are easy to find and then you need what ever the rear iris is tap and a piece of tube    

so what is cheaper

i check my Williams catalog and saw no extension 

love to see what you come up with

mike


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oldair
(@oldair)
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For what it's worth (not much in this case), 7/32-40 will interchange with #12-40 thread - which is equally obscure but tap & die are available from www.victornet.com who have an incredible array of special-thread tooling.

 

Don R.


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marflow
(@marflow)
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so a Diana iris is threaded in 10mm - 1.0 thread just for info 

i'm guessing 5.5mm brass tubing could be treaded in 7/32-40 but you need a piece to thread back to 7/32 and would 5.5 ID be to big 

so you use 5.5 to thread to the sight, a piece of 6.5mm OD with 5.5mm ID for the Williams Iris, they slide on to each other and could glued or solder  together 

untested but an idea 

uxcell Brass Tube, 4mm 4.5mm 5mm 5.5mm 6mm 6.5mm OD x 0.2mm Wall Thickness 300mm Length Seamless Round Pipe Tubing, Pack of 6: Amazon.com: Industrial & Scientific


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Hector J Medina G
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Posted by: @jiminpgh

I am attempting to find/build/fabricate/cobble an extension to move my aperture closer to my eye, by about 3/4 - 1".

I believe I have determined that Williams uses a 7/32X40 thread size. Can anyone help me to figure out what that means is Std screw sizes? There are tons of hollow male-female stand-offs on Amazon that look like just the ticket, but I can't find the right thread size.

If there's an easier way to move a Williams aperture back, I'm all ears. The sight base is as far back as it can go. It works fine with a larger aperture, but I want to use the 1" disk with the tiny hole and rubber eye cup, and that requires near zero eye relief. (I guess I'm trying to build my own 10M match sight.)

There is no "true" conversion, the spec is #12-40:

Ext. 12-40 UNS 2A 0.0009 0.2151 0.2100 - 0.1989 0.1960 0.1835

Which means that the largest screw will measure 0.215 OD, and the smallest nut will have 0.196 ID

So, you would need to start from something that has as close as possible those dimensions and then tap one end and reduce/thread the other with a die.

Taps and Dies are not hard to find under the "UNS" designation (12-40 UNS).

Just one provider:

Die:  

https://drillsandcutters.com/12-40-x-13-16-od-hss-round-adjustable-die-special/

 

Tap:

https://drillsandcutters.com/12-40-hss-plug-tap/

 

Best of lucks and keep us posted!

 

 

 

 

HM


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JiminPGH
(@jiminpgh)
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Topic starter  

Thanks for all the help guys. It looks like my best bet is to buy a 12-40 tap and die, then find a hollow nylon or delrin spacer, tap one end, then reduce and thread the other. Tricky without a lathe, but I'm pretty good at improvising with a drillpress.


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JiminPGH
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Topic starter  

Found this, pretty cheap

https://www.amazon.com/gp/product/B094VWYVVR/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

And these. Way more than I need, but at least I can screw up a few of them before I get it right.

https://www.amazon.com/gp/product/B0951ZCF7S/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

 


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oldair
(@oldair)
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Jim, are you going to the Midwest show in Columbus? If so I can make you a Delrin tube from 3/8 rod that I have tons of - not threaded but 1" long and your choice of OD each end and ID drilled through.  Hate to see ya spend $10 on way too many little pieces.  I'd mail it but that costs near $5.

Don R.


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JiminPGH
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Topic starter  

PM sent


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marflow
(@marflow)
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so i email Williams to find out the thread size was, it is 7/32 or 14-40

and here is what Brian sent me back 

 

Hey mike, sorry for the delay.  Our thread pitch on our apertures is 7/32” x 40.  Hopefully this helps.

so Jim you were right in the first place, are they interchangeable well maybe but the right thread pitch is stated above 

 


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oldair
(@oldair)
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There is a British 7/32-40 size in the "Model Engineer's" standard, available from the UK - one reasonable source with postage cost of 10 GBP is: https://www.tracytools.com/taps-and-dies/model-engineering-taps-dies/7-32-x-40-tpi-me

Don R.


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JiminPGH
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Topic starter  
tube2
tube1
tube3
tube4
tube5
tube6
tube7

So my tap and die showed up today, and it worked PERFECTLY. I will say that this is decidedly NOT a field sight, since the plastic tube is a little fragile, but it WORKS! I guess having proven the concept, the next step would be to find the same bushing in either aluminum or brass, and make a sturdier version. But for now, I'm happy. I can whip up one of these in about 15 min., and I have over 90 blanks.


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Jim Bentley
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It’s good to be “handy”, good job!


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Hector J Medina G
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@jiminpgh

Good Job!

 

 

 

 

 

HM


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Hector J Medina G
(@hector-j-medina-g)
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Just for clarity:

7/32" is 0.2188"

#12 screw is 0.216" OD

Between the "Flats" that all 60 degree threads have/should have, and standard fits (A0 to A5) for screws, both nominal dimensions apply to the SAME thread spec.

Why would we keep both? Dunno, really. It IS kind of funny.

😉

 

Keep well and shoot straight!

 

 

 

HM


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JiminPGH
(@jiminpgh)
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Topic starter  
Posted by: @hector-j-medina-g

Just for clarity:

7/32" is 0.2188"

#12 screw is 0.216" OD

Between the "Flats" that all 60 degree threads have/should have, and standard fits (A0 to A5) for screws, both nominal dimensions apply to the SAME thread spec.

Why would we keep both? Dunno, really. It IS kind of funny.

😉

 

Keep well and shoot straight!

 

 

 

HM

FWIW, the 12-40 UNS tap and die seem to work just fine with the ABS spacers and the Williams sight and apertures. I get a little lost in the sauce when it comes to thread specs, and I'm not REALLY sure that there isn't some forced conformance going on here with the softer ABS, but they spin on and spin off without undo effort. It was a fun adventure, with the outcome I was looking for.

 


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Jim Bentley
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@jiminpgh 
In this application everything is fine. If it was a part for the space station there may be a slight concern 😀


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MDriskill
(@mdriskill)
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Posts: 276
 
Posted by: @hector-j-medina-g

Just for clarity:

7/32" is 0.2188"

#12 screw is 0.216" OD

Between the "Flats" that all 60 degree threads have/should have, and standard fits (A0 to A5) for screws, both nominal dimensions apply to the SAME thread spec.

Why would we keep both? Dunno, really. It IS kind of funny.

😉

Keep well and shoot straight!

HM

Just an aside: the British Parker-Hale eyepieces are also nominally a 7/32 - 40 thread...but will NOT fit most US sights. I may be wrong but I think they use a 55-degree thread angle, so are a bit larger in overall diameter (is this the "7/32 - 40 Model Engineer" thread that Don R posted above?).

P-H stuff WILL fit the one Lyman sight that I have, also nominally 7/32 - 40, but not Williams or Redfield, etc. A real shame, as P-H made lovely eyepieces, small adjustable irises, etc., that would be awesome in that Williams!

And whilst ruminating on trivia irrelevant to the OP 😬, I will add that the standard thread for German eyepieces since at least the 1950's, is not 10.0 x 1.0mm, but the rather odd 9.5 x 1.0 mm. 


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Hector J Medina G
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Posted by: @mdriskill

Just an aside: the British Parker-Hale eyepieces are also nominally a 7/32 - 40 thread...but will NOT fit most US sights. I may be wrong but I think they use a 55-degree thread angle, so are a bit larger in diameter. Maybe this is the "7/32 - 40 ME" thread that Don R posted above?

P-H stuff WILL fit they Lyman sight that I have - also nominally 7/32 -40, but not Williams or Redfield, etc.

All of which is a real shame, as P-H made some gorgeous small adjustable irises, etc., that would be awesome in a Williams!

The history of threads and screws is the history of industrialization. We think that industrialization started in Manchester in the late 1700's->1800's, but that is far from true:

https://www.ctcustomairguns.com/hectors-airgun-blog/what-links-airgunners-to-the-chinese-warriors-of-the-13th-century  

As a Manchester's UMIST (now defunct) Alumnus (1979-1982), I used to have a high regard for Sir Joseph Whitworth, and I still do in some aspects (mainly metrology), but I have "cut him down to size" in the sense of his altruism.  😉

The 55° thread (Whitworth thread), was standardized by the BSI (British Standards Institute) many years ago, as a way to keep the "Frogs" out of the machinery race. So, yes the MAIN idea is make things NOT fit, even if the "spec" is, apparently, the same.

P-H did make wonderful things, I still have a P-H rear sight that I will someday mount on an airgun (side-mounted), maybe when we can come up with a "replica" of the SMLE as we did with the K98 (piston). I'll find the right place for it sometime.

Merit is back in business making Irises, not all of them, but the smaller ones, yes. If you want one, just let me know.

Keep well and shoot straight!

 

 

 

 

 

HM


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Hector J Medina G
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Posted by: @jim-bentley

@jiminpgh 
In this application everything is fine. If it was a part for the space station there may be a slight concern 😀

Jim;

Would you be astonished if I tell you that the space station uses the LOSEST tolerances in some of the threads they use?

Reason is simple: When the ISS is in the sun, temps on surfaces may reach quite high points, when it is in the shadows, the coldness sets in. A very tight thread would seize simply by temperature differences along the "day". They also pay a LOT of attention to which metals can be in contact with others.

Aerospace companies make mistakes, if you are interested, just read how the Hubble needed "glasses" to correct its focal distance because the company that ground the main mirror was VERY conversant with looking DOWN on earth, and not totally competent about looking OUT into the cosmos.  😉

Keep well and shoot straight!

 

 

 

 

 

HM


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MDriskill
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Posted by: @hector-j-medina-g
 

Reason is simple: When the ISS is in the sun, temps on surfaces may reach quite high points, when it is in the shadows, the coldness sets in. A very tight thread would seize simply by temperature differences along the "day". They also pay a LOT of attention to which metals can be in contact with others.

Very interesting! Similar story...a friend of mine was a crew chief for the Lockheed SR-71 Blackbird spy plane. He described it as so leaky on the ground, you needed an umbrella to walk beneath! But in action at mach 3, it got several inches longer due to the heat of air friction - and all its pipe joints and fasteners tight as a drum.

The airframe got so hot that the crew typically exited vertically, via a specialized crane.


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Hector J Medina G
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Yup!

Even though the SR71 is almost completely sheathed in Titanium, the air friction at those speeds make the "envelope" grow substantially (some spots reach 1,000° F). It is also a function of the slenderness of the aircraft itself. The windshield itself operates at 600 °F.

Things you learn when you visit the Smithsonian's U-H aviation museum, LOL!

 

😉

 

Keep well and shoot straight!

 

 

 

HM

 


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RockDoc65
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I used to be a AH-1S (Huey Cobra) crew chief. Sometimes our aircraft would "grow" a bit during flight. This was not due to thermal expansion but rather the accumulation of dead bugs and vegetation on leading edges. Bugs, sap and plexiglass. The horror. This post was mainly for my own amusement. Feel free to ignore it.


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JiminPGH
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Topic starter  
Posted by: @rockdoc65

I used to be a AH-1S (Huey Cobra) crew chief. Sometimes our aircraft would "grow" a bit during flight. This was not due to thermal expansion but rather the accumulation of dead bugs and vegetation on leading edges. Bugs, sap and plexiglass. The horror. This post was mainly for my own amusement. Feel free to ignore it.

I REALLY appreciate the Apocalypse Now reference. Well done. Amazing how a simple thread-size question has gone to the ISS, SR-71, and now this! You guys are the best!

 


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RockDoc65
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We do tend to drift a bit.

scan10

 


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JiminPGH
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Update: I found I need more wall thickness to make a less fragile extension. I bought some of these:

https://www.amazon.com/gp/product/B00FGAB35K/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

I will need to reduce the male end, and counter-bore the female end prior to threading.

What have I learned so far? A: It works! 2: ABS is pretty darn fragile when the walls get thin. (c): I REALLY could use a micro-lathe. (Wife said Hard No!)

Still having fun. I'll get this!


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JiminPGH
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Topic starter  

Well, problem solved. Williams FP GR TK and BKL riser. I now have a proper 10M sight for my Tau 200 Jr.

tau200sight1
tau200sight2
tau200sight3
tau200sight4

 


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