S&W No. 3 Extractor Return Spring

[wlw-19958]

Hi There,



Well, this same early No. 3 always acted anemic when it came
to the return of the extractor after extraction. Almost always,
I would have to help it by pushing down with my finger.

Initially, I wasn't sure what the problem was but after collecting
a couple more no. 3's, I can see the spring isn't right. The cur-
rent spring was made from .018" wire and only has 19 turns
(plus its diameter is larger than the others in my collection).
Measurements of the springs from other no. 3's shows me that
the wire should be .027" in diameter and have 31 coils. The
outside diameter of the spring varies from .200" to .202" de-
pending on which example I measure. It took me some time
to get the correct pitch but I found .069" to work well.
I couldn't find music (piano) wire exactly .027" in diameter
but .026" was a standard size, so I went with that.

The biggest problem (for me) is to determine the correct dia-
meter mandrel for winding the wire around to get the correct
diameter spring. It isn't quite as straight forward as one might
think.

One might think that If one wants a .200" diameter spring,
and the wire is .026" in diameter, well then .200 - ( 2 X .026 )
= .148" mandrel would be right size, but it isn't. You see, the
coiling of the spring using music wire (which is a high carbon,
high tensile strength steel wire), there is going to be a certain
amount of "spring-back" once the tension is released from
winding the spring around the mandrel.

One could experiment with smaller and smaller mandrels until
the right size is found but there are formulas out there for
determining the correct size. I don't know them but a search
on-line gave me a website that will do the calculations based
on the data one provides. Using that websites calculations, the
correct size mandrel was determined to be .128"

Now, one point I will make is, not every manufacturer's music
wire is exactly the same and the amount of tension I place on
the wire while winding may not be exactly the same as speci-
fied. But, it gets me close. I found I got the correct OD using
a .125" (Yes, 1/8") mandrel.

This variance wasn't totally due to the software. It was partly
due to the fact that I was measuring the diameter of my other
examples while under tension. Coil springs get bigger in dia-
meter as they are compressed and I failed to take that into
account. Plus, I wanted the springs to be .200" (I was getting
.202" with the .127" mandrel and .128" steel stock wasn't
available from my supplier).

I know I am getting way too "nerdy-tech" here so I'll stop.
Lets just say, the new spring corrected the problem. Thanks
for listening.


Cheers!
Webb

 

[Alk8944]

Obviously you have done this before, so I won't give you any advice on how to wind a spring.

 

[wlw-19958]

Hi There,

Obviously you have done this before, so I won't give you any advice on how to wind a spring.

Well, yes. I have wound coil springs before but I'm self taught
and I am always interested in learning more. If people are in-
terested, I will post some pics of the lathe set-up I've been
using. If one has any advice, I will listen. Thanks!


Cheers!
Webb

 

[shown50]

Hi There,





Well, yes. I have wound coil springs before but I'm self taught
and I am always interested in learning more. If people are in-
terested, I will post some pics of the lathe set-up I've been
using. If one has any advice, I will listen. Thanks!


Cheers!
Webb

I’m absolutely interested in seeing your set up! Can you link the website you used for the math? Thanks for the detailed write up, it definitely helps people like me who are still learning how to repair these guns when parts aren’t available anymore.

 

[mmaher94087]

Webb, I'd like to see your setup too. I don't have a lathe so I'm pretty well stuck with off the shelf coil springs.

 

[wlw-19958]

Hi There,

Can you link the website you used for the math?

The website I have been using that I like is the following:


CGTK - Spring Calculator


I generally use FireFox but I had some trouble with Chrome
when I tried to open it from a DuckDuckGo search. If you
copy and paste it into the address line of your browser, it
should work.

The site is set up initially for metric but you can change that
by clicking the appropriate entry after clicking the down arrow
on the box at the top. There are other boxes you set for your
situation. The 7 top parameters are all you need to set. The
others will be filled in automatically based on the information
in those top 7 boxes.

I will try to get a photo essay up on how I made the spring
later.


Cheers!
Webb

 

[mmaher94087]

Dang! I haven't consulted my copy of Machinery's Handbook since the late '60's. I still have it on the shelf... somewhere.

 

[wlw-19958]

Hi There,

I have an old copy of The Machinery Handbook (1955 or 1958).
I prefer the older copies because as new information and tech-
niques (like CNC and EDM) are developed, some of the older in-
formation is discarded to make room in the handbook for the
new info.

My lathe has a internal spindle taper of Morse Taper 4-1/2 and
the more current versions of The Machinery Handbook do not
list it in the spindle taper section anymore but my 1955 version
does. Only a handful of lathe manufacturers use it (like Rockwell,
LeBlond and Clausing). I have several lathes but I like to use my
Clausing 5914 most (plus most of the others are in storage).

Sometimes, on machinery sites people would argue about whether
Morse Taper 4-1/2 ever existed and I would scan the page from
my copy of the handbook and post it and say “oh yes it did and
here’s the proof!”

Anyway, this has little to do with Smith & Wessons so I will stop
droning on.

Cheers!
Webb