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It is currently Wed Apr 17, 2024 11:25 am
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[ 4 posts ] |
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Question about fitting a used replacement slide
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Nate
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Location: South Puget Sound (sounds more hoity toity than Puyallup) Joined: Sat Oct 22, 2011 Posts: 1351
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I have a Sig P6. I happened to find a slide that I liked better than the original one, so I bought it. I thought it would be plug and play, but in the end, it didn't work out that way.
It's like the overall height of the replacement slide was about .002 taller than the original. The net result was that the bottom of the slide was pretty tight against the frame rail.
I removed some material from the bottom of the replacement slide until the clearance was about the same as the original.
Do they go through similar steps in the factory, sort of a final fit?
These are late '70's slides. It doesn't seem like that long ago to me...were manufacturing tolerances that loose back then/
Does this seem like the right way to have worked through this?
Are there any other checks? This slide has a more snug fit than the original slide. The original feels all sloppy and loose by comparison. But, I don't know what "factory fresh" should feel like, as a point of reference.
_________________ Tier 9 Operator
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Tue Jan 17, 2012 11:20 pm |
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deadshot2
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Location: Marysville, WA Joined: Fri Jul 22, 2011 Posts: 11581
Real Name: Mike
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To a point that's what happens. Frames and Slides are machined to fairly close tolerances but different "batches" can have slightly different measurements. Depending on the "shop standard" tolerances can be from +/- .0005" to +/- .005". If these are stacked then things can get real tight. When one is assembling the pistol they check the movement of slide to frame. If the slide doesn't move with the desired "feel" another may be tried in order to find the right combination of tolerances. Sometimes some "lapping" is done where an abrasive is added to the rails and the slide operated until it's just right.
When I was in the Army I was assigned to a Company with a Small Arms Repair Section. We'd get 1911's by the crate for repair. We'd often try dozens of slides on the same receiver until we got one that fit just right. Also did the same with barrels and barrel bushings. When we had one just right, magically, someone in the Section got that pistol "issued" to them while their old one was turned in. Some real nice scores came from the Small Arms Section during annual quals.
One thing to make sure still functions after removing the metal from the bottom of the slide is the disconnector. Make sure that the pistol still can't be fired out of battery. With the firearm unloaded, cock it, press the slide back very slightly and pull the trigger. See how far it can be pressed back while still dropping the hammer when you pull the trigger. It should ve a very small amount. On my Sig P-229 it's less than 1/16" before the disconnect occurs and the hammer isn't released. On my CZ75 SP-01 it's more like 1/8" but before that the hammer is pushed back so it can't hit the firing pin.
Just be sure to check function of all safety features and then go shoot it.
In closing, CNC machines were still in the primitive stages in the 70's. Today they're far more sophisticated and even more "Gee Whiz" but more for how much they can do and also as accurate as they are. Finished parts are able to be mated with less "hand work".
I had the privilege to visit a factory that made high pressure pumps a couple of years ago. They had a machine that the operator stood at one end putting raw castings on a jig attached to a conveyor chain. When he did that he reached to the other side of his area and removed a finished part. He then left until he heard the alert tone telling him the new part was finished and it needed another raw casting. During the process the machine automatically positioned the work piece, changed tool heads as needed, and while doing so machined all sorts of rails, holes, and shapes. The machine tolerances were +/- .0003" and had a cost of just over $1,000,000. Now that's "Gee Whiz".
_________________ "I've learned from the Dog that an afternoon nap is a good thing"
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"For he to-day that sheds his blood with me Shall be my brother" - William Shakespeare
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Wed Jan 18, 2012 7:50 am |
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Nate
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Location: South Puget Sound (sounds more hoity toity than Puyallup) Joined: Sat Oct 22, 2011 Posts: 1351
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Excellent feedback, thank you, exactly what I was looking for.
I did the safety check you detailed with the original slide, and then with the replacement slide. They both disconnect at the same relative position. Glad you mentioned that, I did not know to check it.
I asked this question on a sig specific site also, but the feedback there ranged from "you'll mess up your sights" to "breaking the frame if it wasn't fitted right".
I'm going to take both the original upper and this "new" one to the range and do some comparison shooting. The new one came with a numbers matching barrel also, so all I have to do is pop off the old one, swap over the guide rod and spring, reinstall, and shoot.
I guess the best I can do is watch the frame for excessive wear patterns, and worry about an adjustment if/when that happens.
The long term goal is to get the frame and slide refinished anyway.
If I did see wear a wear pattern developing, would that be an opportunity to use some lapping compound around that area, dress it up, so to speak, prior to getting it refinished?
Thanks.
_________________ Tier 9 Operator
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Wed Jan 18, 2012 10:28 am |
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Nate
Site Supporter
Location: South Puget Sound (sounds more hoity toity than Puyallup) Joined: Sat Oct 22, 2011 Posts: 1351
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Well, I kinda answered my own question. Don't know if it's conventional or not, but wanted to put it out there for anyone like me who is doing some of this stuff for the first time.
I found a book that went into pretty good detail about fitting up slides to frames, and it said to use lapping compound for a final fit.
But, the finish on the frame is in really good shape and I was afraid the lapping compound would wear through it. So, how to "lap" the slide without touching the frame...hmmm....
I have micro grit polishing paper I use to polish guitars, and I was able to sandwich one between the frame and slide, and then just move the slide back and forth over the paper...seemed to work out well.
Before the polishing paper routine, I would have to use a light finger pressure to move the slide back and forth on the frame.
The book I read said that the slide should move without assistance. After a few strokes across the polishing paper, it does just that.
As I was working through this, I also discovered to check the freedom of slide movement with the gun in three different orientations...gun in normal position, and also oriented on each side. When I held the gun in my hand in shooting position, and tilted it up and down, the slide moved freely. When I held the gun in normal shooting position, rotated 90 degrees to the left and then tilted it up and down, the slide moved freely. When I rotated the the gun 90 degrees to the right, and then tilted it up and down, the slide would not move freely. A couple more passes over the polishing paper on the left side of the frame, and now it's really smooth.
_________________ Tier 9 Operator
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Sun Jan 22, 2012 7:16 pm |
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