Thanks Magnum Nut. This is clear, concise and helpful.

What year did the internal locks start being used?

quote:

Originally posted by readyme:
What year did the internal locks start being used?

2001

Feeler gauge inspection


Here are the general specs for basic checking on S&W revolvers.

Whenever I check the specs of S&W revolvers there are 3 things that I check, air gap, head space and endshake.

In a nut shell here is how I do it.

AIR GAP:
Proper air gap on S&W revolvers is .004-.010 inch. Rotate the cylinder and check it in more than one spot. The cylinder won't be perfectly square, it will vary some. Measure it at the forcing cone. Too little gap the gun will jam, too much and the gun will start spitting, plus lower bullet velocity and accelerated top strap erosion.

Endshake:
Set end shake for less than .002". Here is how I test it. Push the cylinder forward, check it. Pull the cylinder back, check it again. The difference is endshake. Measure it at the forcing cone.
If I need to adjust it, I use end shake bearings, instead of peening or flaring the yoke's barrel. A gun needs some endshake to run, too little and it will jam, too much creates all kinds of problems, possible light hammer strikes, poor carry up etc.

Head space:
Here's how I test it: With new or once fired cases in all chambers (no primers). Wedge the cylinder back by placing a shim between the barrel and cylinder face (a gap gauge works well. This forces the cylinder back where the extractor's hub is bottomed out on the recoil shield. You should have .008-.012" (.010" optimum) gap between the case heads and the firing pin hole on the frame.

Keep in mind the ejector and cylinder are made and fit at the factory to work together for proper head space. Swapping parts may throw off the head spacing.

Normally, head space doesn't change unless someone files down the hub of the ejector.

I added the gage specifications below for each particular caliber (from the armorer's manual):

38,357,41,44 .060"-.068"
22 magnum .004"-.008"
45 ACP .090"-.094"
45 Long Colt .060"-.068"

38,357 w/cylinder Counter Bore .012"-.018"

In addition no revolver should be adjusted to a single action trigger pull of less than 3 LBS.

This message has been edited. Last edited by: 500 Magnum Nut,

500 Magnum Nut, Where would we be without you?!? Thanks again for a great post!

Can you recommend a good set of feeler gauges for S&W revovler purposes?

Regards,
Perp

quote:

Originally posted by perpster:
Can you recommend a good set of feeler gauges for S&W revovler purposes?

A good set is MITUTOYO's which can be ordered thru Brownells. http://www.brownells.com/aspx/NS/store/ProductDetail.as...&title=FEELER+GAUGES

They come in metric or inch, order the type you prefer.

quote:

Originally posted by 500 Magnum Nut:

quote:

Originally posted by perpster:
Can you recommend a good set of feeler gauges for S&W revovler purposes?

A good set is MITUTOYO's which can be ordered thru Brownells. http://www.brownells.com/aspx/NS/store/ProductDetail.as...&title=FEELER+GAUGES

They come in metric or inch, order the type you prefer.

Not that I'd order metric anyway, but the metrics are $60 while the US are $24, and there's only 2 more in the metric set!

Might want to keep this one up here too. "What does MIM mean"

http://smith-wessonforum.com/eve/forums/a/tpc/f/530103904/m/1311012512

Originally posted by jengel:
I'd like to add this to your post.

Here is an older post that I have copied here, what is MIM?

By popular request, here's the post from Mr. Herb Belin of S&W -----------------------
"I have read with much interest the many comments in this forum pertaining to MIM, MIM Parts and the use of same in a S&W product. So far I have come away with several impressions and they are "people in general don't like/trust MIM parts" and "no one has said why" I will take a stab at this issue and see where it goes.

As background to our decision to use MIM in some areas of our Mfg Process we took a long hard look at our "Life Time Service
Policy". It was clear to us that any change in any of our products such as the use of MIM components had to show equivalent or better performance and durability to those components that were being replaced or the "Lifetime Service" would haunt us forever. The second consideration was to determine if the change was too radical a departure from S&W mainstream design.

For the performance and durability issues we decided that if MIM could be used for the fabrication of revolver hammers and triggers successfully this would truly be an "Acid Test". There is nothing more important to a revolvers feel than the all-important Single Action Sear that is established between the hammer and the trigger. Mechanically few places in a revolver work harder than at the point where the hammer and trigger bear against each other. If these surfaces wear or loose there "edge" the "feel" is lost. Initial testing was on these two critical parts. Over time we arrived at a point where our best shooters could not tell the difference between a revolver with the old style hammer and trigger and the new MIM components. Special attention was given to their endurance when used in our very light Magnum J frames such as the early prototype 340 & 360 Sc's. None of our revolvers work their components harder than these small magnum revolvers. Throughout this testing MIM held strong and finally we determined that this change judged on the basis of durability and feel was a good one.

The second area of concern to S&W was our customer’s reaction to this departure from the traditional. Many heated, intense discussions resulted but in the end the decision was made to move ahead with MIM.
The issue of cost was only one of the considerations in making this decision. Equally as important was the issue of part-to-part uniformity and the result of this of course is Revolver-to-Revolver consistency. We found that revolvers that used MIM hammers and triggers required almost no Fitter intervention in those areas during final assembly and final inspection and Trigger Pull Monitor rejection rates dropped markedly on finished guns. From an internal process point of view it appeared a "Winner".

Lets shift gears for a moment and talk about the MIM process. It is unclear to me as to the reason for many of the negative feelings on the forum concerning MIM. Typically when people complain and aren't specific in the reason why, the problem is often created by a departure from the "Traditional". Perhaps that is indeed what is bothering some people when they view MIM.

The term MIM stands for Metal Injection Molding. It holds some similarities to Plastic Injection Molding and many differences as well. To start we would take a finally divided metal powder. This could be stainless or carbon steel. Today even Titanium is being used in some MIM fabrications. We would mix the metal powder and a thermoplastic binder (generally a Wax) forming slurry of sorts when heated and inject this mix into a precision mold and finally form what is known as a “Green Part". This part is roughly 30% larger than the finished part it will become at the end of the process. Interestingly enough the Green Part at this stage can be snapped in two with simple finger pressure. The Green Parts are then placed in a Sintering furnace filled with dry Hydrogen gas and the temperature is brought almost to the melting point of the metal being used. Over time the "Wax" in the Green Part is evaporated, the metal fuses and the part shrinks 30% to it's final correct dimensions. At this stage of the process the MIM part has developed 98 to 99%of the density of the older wrought materials and a metallurgy that is almost identical. Dimensionally it is finished and no machining is required. However the job is not yet done and the MIM parts are brought to our Heat Treat facility for hardening and in the case of Hammers and Triggers, Case Hardening. Depending on the particular metal alloy that was used at the start of the process we apply a heat treat process that is the same as would be used if the material were the older wrought style. Final hardness, Case thickness and core hardness are for the most part identical to parts manufactured the older way.

Lets look for a moment at how we achieve dimensional precision when comparing these 2 processes. The old parts were each machined from either bar stock or a forging. Each cut and every resulting dimension was subject to machine variations, Cutter wear, operator variations etc. If every operation was done exactly right each and every time and the cutter didn't let you down you would have produced a good part but sometimes this didn’t happen resulting in a rejected gun and rework or in the worst case an unhappy customer. With MIM parts you must still machine to very high tolerances and your cutters have to be perfect and your machinist has to be highly qualified but all of this only has to come together one time. That time is when the injection mold is made. Typically a mold for this process costs S&W between 30,000 and 50,000 dollars. Once it is perfect every part it makes mirrors this perfection and you have in my view a wonderful manufacturing process.

Hopefully this description will help us all better understand the MIM process.
Please forgive the spelling errors and misplaced punctuation. I have no spell checker on this and the phone continues to ring!

Have a Great Weekend,
Herb

Additional Point.
Currently S&W is paying about $1.20/Lb for stainless steel bar stock. Raw MIM stainless steel inject able material costs $10.00/Lb."

And there I was thinking MIM meant "Made in Merica", after S&W stopped making their guns in Japan.

Interesting read. MIM must really cost less overall if the MIM stock costs nearly 10x the cost of bar stock.

CORRECTIONS to STANDARD CATALOG OF S&W, 3rd Ed., by Nahas & Supica are posted here:

http://armchairgunshow.com/scsw3-corrections.html

Special thanks to Richard Nahas for compiling this list. -- Jim

Jim,
On page 226 under Model 64 NY-1, where it lists the production numbers for these guns, it states 516 of the 3"rb then a little later states 96 of the 3" rb. One of them is probably square butt, I'm assuming.
Thanks,Mike

Hand and Torsion Spring

Cylinder Stop Terminology

A cylinder stop is fit to the cylinder first. You fit it to the smallest notch in the cylinder, and they will vary a little. Then you fit it to the trigger. Make sure that when the trigger pulls it down, that it does not pull the ball out of the frame window. If you leave it set where the ball drops below the opening, it can get offset to one side and hang up inside the frame.

When originally fitted, the stop is timed so that at no time the top of the ball drops below the edge of the window in the frame. If it does, it can stick in the down position. So, they tend to not have them rise above more than they have to lock the gun. On the top of the cylinder stop right behind the start of the hook, is an adjustment step. By filing it down, you allow the cylinder stop to go further up through the window and engage the cylinder notches deeper. The adjustment step is for when it wears, you can adjust it. By having the stop rise a little more, it compensates for wear in the notches and locks the cylinder better. If that does not rise up high enough to lock the cylinder, then you will need to fit an oversize stop.

When fitting an oversized stop, measure the width of the stop where it engages the cylinder and make sure you get one at least as wide. You can end up with an undersized stop that will be worthless to you.

Yoke Terminology


ENDSHAKE REPAIR
You have 3 types of fixes for endshake.

First way is peening the yoke barrel to stretch it. Some smiths do it this way.

The 2ND way is using a tubing cutter sort of tool and squish the barrel to stretch it. This is the S&W way.

The 3RD way is the best way in my opinion. This way uses what they call endshake bearings. They are hardened stainless steel shims that fit inside the cylinder and add length to the yoke barrel.

I use a 3/8 endmill (or swap it for a dremel "type" stone if you wish) and rub the sides down to make the endmill safe (or stone safe) so it won't cut on the sides. Using a drill press place the cylinder in a vise. Put the endmill in the chuck. Using the quill insert the tool inside the cylinder. Turn the chuck by hand (NO POWER) and clean up the bottom of the cylinder. You want to remove that ridge made by the yoke. Then using a yoke squaring tool, trim the yoke barrel so it is clean and square. Add a few drops of oil on the bearings then place the desired amount inside the cylinder. Reassemble the cylinder on the gun and check your work. Ideal endshake is less than .002 inch.

This “new way” won't damage the yoke and if done properly will last for thousands of rounds.

This message has been edited. Last edited by: 500 Magnum Nut,

MIM Trigger and Torsion Spring

If you get in trouble and pop that spring off the hand, here is a picture of how it looks so you can put it back on.
Short spring side just gets placed into the bottom of the trigger (it fits into a "blind" cutout)
Long spring side gets placed behind the hand pin.

Probable causes to a cylinder that doesn't open or close smoothly:

loose extractor rod
bent extractor rod
loose thumb piece nut
short or worn center pin
end shake cylinder or yoke
dirt under extractor
yoke out of adjustment
worn bolt
worn locking bolt
worn yoke button
worn yoke screw
tight yoke screw
ammunition rubs frame or primer flow
worn recoil plate firing pin bushing