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kcd19

STI slide to frame fit - getting started

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kcd19   

trying my hand at fitting a new slide/frame & would like an opinion. i've attached the dimensions i've measured of the two pieces.

all of the measurements seem to line up more or less in-spec/tolerance for getting things fit up, with the exception of what my initial removal of material should be.

the rail (male) portion of the slide is almost 0.010" thicker than the corresponding dimension in the frame. (measurements A & H in my drawing)

At this point, the slide doesn't even come close to getting started on the rails; obviously, material needs to be removed from one or the other of the surfaces - either the bottom of the slide needs to be flattened by that amount, or the bottom side of the slide rail would need to be adjusted. in my mind, it would be more prudent to work the bottom of the slide to gain clearance so as not to make the frame rail smaller (B measurement), as it's already very close to matching the slide spec. can anyone weigh in on whether i am on the right track with that observation? (or any other suggestions..)

the other thing i've wondered about is the differences between my measurements D & H - (inside width of slide rails) - is the ~0.010" difference going to matter significantly, or will the slide need to be tightened. I've measured some of my other 1911s and most of those dimensional differences (vertical/horizontal play) seem to be held to under 0.010 for the most part.

thanks for any insights or ideas.

post-28274-0-97475000-1359841037_thumb.p

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Area C and H for the moment, and test fit. The other dimensions look pretty good. I would assume (hate that word) that you would want to machine as tight a tolerance as possible, and the most critical tolerance to be the rails.

But I am not a gunsmith by any means, just making a SWAG (Scientific Wild Arse Guess)

Edited by Got Juice?

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ltdmstr   

Machine C width and H height to the point where the parts just start to go together. Then hand lap the rest of the way.

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ajg308   

I dont have equipment other than bench and hand tools. I use a file to get it close and lap it after that. If it is hard lapping I will use dykem blue to find the high spots. I also use dykem blue to make sure I am filing it level or getting just the spot I want.

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RPatton   

I think this falls under the "or any other suggestions.."

Your member title may be "looks for range" but it should be "looks for gunsmith".

The first rule of gunsmithing is "Destroy the cheapest part first.".

In your case there are NO cheap parts but start with the slide.

I don't know where you are but I would find a USPSA match and ask around. Look at a few examples of some gunsmithing, then take it to someone that some experienced shooters that have invested >$2000 with. Let them fit the slide to the frame. A local guy here charges $125. It would be money well spent.

After that you can cobble together the rest. Properly fitting a barrel is another story.

Does the term "past the point of no return" mean anything to you.

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ltdmstr   

If it's a one time deal, you're better off paying someone to do it for you. If you plan on doing more, you gotta start somewhere. When I started out I used a 8x12 surface plate and sandpaper to take down the surfaces and then hand lapped. A real pain in the butt and much manual labor. But I managed to build quite a few half-inch guns with no mill and no lathe. Just hand tools and a dremel. So it can be done if you understand what you're doing.

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skip62   

Get Kuhnhausen's book on the 1911. There is much more to this than you think.

+1, as tambarika, it's more than just getting those 2 parts to fit together. Everything about a 1911 effects something else, that's why there are so few 'good' gunsmiths in the country.

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Get Kuhnhausen's book on the 1911. There is much more to this than you think.

+1, as tambarika, it's more than just getting those 2 parts to fit together. Everything about a 1911 effects something else, that's why there are so few 'good' gunsmiths in the country.

first step: a machined plate is inserted into the slide rails. the slide is placed on the milling table and the plate is indicated flat. the bottom of the slide is then milled to the indicated plate to make the bottom of the slide parallel to the slide rails.

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GuildSF4   

I fit several when I worked for Guy using the draw file technique (no machining), then lapping. This is not for everyone, you can easily go too far or uneven and end up with a loose gun. If you wish to do this go slow and make sure it is even, good luck.

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ltdmstr   

Yep. Hand filing anything for than a couple thousandths and keeping things even is a lot more difficult that most people expect.

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DJCAREY   

I got AGI's videos on building a 1911. Of what i have watched of them they look good. They show you how to do it with a file and mill.

Sent from my SCH-R530U using Tapatalk 2

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GuildSF4   

The AGI videos that I have seen do a pretty good job.

I heard one time you should fit the slide to the frame so if you ever have to fit a new top end the frame won't be too small...

Draw filing is done on the slide, I haven't yet done any filing on a frame to fit the two. (My choice would be to mill the slide before milling the frame, however if the frame rails are way oversize then maybe.)

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I do not cut the Slide female rail nor would I. It would require a keyway cutter and would be a very difficult cut. That dimension is pretty consistent on the slides I have fitted. As a matter of best practice if I am building a custom gun I would want only one slide fit. But if 2 top ends is the goal I would fit to the largest dimension and cut the fame to that spec. The only time that slot would be cut is during lapping of the slide to the fame. The slide fit has very little to do with accuracy and a few thousands would not be a big deal.

I can't speak for other gunsmiths but I have never seen that area cut as a part of fitting a slide.

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