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  #1  
Old 05-06-2008, 05:52 PM
cowboy1 cowboy1 is offline
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Adjustable sight install info

Would someone know what the dimensions of the dovetail of a STI adjustable rear sight is? I purchased one for a project I Ďam doing, and it came with no information as to what it is. I am not sure if it is a 60 or 65 degree, and the width of the cutter I will need. I have a Novak cutter but it is too wide. Any information would be helpful. I like the Novak because they come with machining instructions and dimensions, but this is what Iíve got. If someone wants to post complete milling dimensions that would be really great.
Thanks
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  #2  
Old 05-06-2008, 07:33 PM
LogicGS LogicGS is offline
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They use Bomar style cuts: 60 Deg x .359"

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  #3  
Old 05-07-2008, 08:09 AM
cowboy1 cowboy1 is offline
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Thank You

Thank you
It lookled like a 65 degree when compaired to another. I will have to order the 60 degree cutter. Never the one you have on hand.
Keith
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  #4  
Old 05-07-2008, 12:14 PM
cowboy1 cowboy1 is offline
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They Think

I just got off the phone with STI and they also "THINK" it is a 60 degree X 300 or 400 something. Not really the responce I was expecting. I also ordered a 60 X359 cutter from Brownells.
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  #5  
Old 05-08-2008, 09:35 AM
LogicGS LogicGS is offline
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Quote:
Originally Posted by cowboy1 View Post
Thank you
It lookled like a 65 degree when compaired to another. I will have to order the 60 degree cutter. Never the one you have on hand.
Keith
Tell me about it. Hundreds of endmills and drills in this shop, and yet every time I start on a project and run up a tool list, I always have to order something.

I checked my STI catalog after your last post, and it says right under their sight listings what dovetail they fit.

You must have gotten the retarded salesman when you called STI, 'cause the info is right there in black and white if he'd have bothered to look in his own catalog.
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  #6  
Old 05-08-2008, 09:43 AM
Lppd4 Lppd4 is offline
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I assume you are talking about the STI Bomar type adjustable sight? If so check out Blindhogg.com for info on the sight cut for a Bomar I think it takes the same cut.
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  #7  
Old 05-11-2008, 06:57 PM
cowboy1 cowboy1 is offline
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Well this project has turned into the slide from HELL. The welding part turned out somewhat OK after the second time. Now after welding on the slide, is so darn hard that it is eating up cutters left and right. At first I tried to cut the weld spots down to some manageable size and went through 3 HHS cutters. OK now on to carbide, went through 2 of them, finally got some from the Production tool store here coated with Spectrum, very expensive, but it was able to cut it. Finally got the rear sight cut out and fitted. Started the front dovetail today, again one 3/16 HHS and one Carbide cutter to the trash. Tomorrow I go back to Production too and get another coated in Spectrum to rough out the front dovetail. Hopefully my Carbide dovetail cutter from Brownells will last. Not sure what to use for the 1/16 pin hole and the number 31 drill for the adjustment screw in the rear sight. From what I have got into cutters alone, I donít think I will ever break even this year, as I am a small shop just getting started. On a $30 dollar project I have spent over $200 in cutters and re-sharpening fees and dovetail cutters and other odes and ends. I have learned one thing; I will never work on another welded project again. I just wanted to tell my story.
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Old 05-11-2008, 08:07 PM
Greg Derr Greg Derr is offline
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Are you " hogging" The center of the dovetails first? What rod did you use to weld? I like to use a slightly softer rod on sights since I know I'll be cutting them again. On the carbide cutters from Brownell's I go 1200rpm with flood cooling. For the #31 hole I would go with carbide- hate to cut a crooked hole for that one. Greg
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Old 05-11-2008, 11:17 PM
blindhogg blindhogg is offline
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cowboy1
You learned the lesson I got about 6-7 years ago. That is not all welders know how to weld on hardened steel, if done right its not a problem but if done wrong I would not touch it with a ten foot pole.
Since I went through my fiasco I only let extremely talented welders weld up slides for me. So far EGW and Pete Single have welded for me and both cut afterwards like mild steel. No problems at all.
You live and you learn.
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Old 05-11-2008, 11:49 PM
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pistolwrench pistolwrench is offline
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The front sight area is one that can be spot annealed. I've done it on numerous occasions. I'll give a brief description of my method, but I advise practicing on a junker before you try it on a viable slide.
Oxy-acetylene torch, #00 tip, small hot flame. Heat the area of the front sight to a red glow, you will notice the weld material will be a different shade of color. The red spot should never grow larger than a nickel or so. Continue the heat until the two areas are approx. the same color. Slowly back off the flame and tease it down in temp for a minute or two. Push the slide end into a coffee can filled with sand. Allow to cool. I'll usually do this twice. The colors homogenize more readily the 2nd time.
This is not advised in the area of the rear sight as the heat affected zone will be quite large due to the thickness of the cross section. You don't want a soft breechface or disconnector cut.
If needed, I'd be happy to lend a hand.
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  #11  
Old 05-12-2008, 12:17 AM
LogicGS LogicGS is offline
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I'm not a professional gunsmith, but I am a pretty decent machinist, and I have ran into machining a weld a few times before.

Sometimes you can't do anything with it, but if the slide is an alloy strong enough to live without a heat treat in that area, you can heat and anneal that spot. If you're not careful with your cooling though, you can warp the part doing this.

It may be better to anneal the whole thing, do your machine work, then have it heat treated again, but it might move around on you depending on the stress in the part.

If it's been welded on already, whatever heat treatment the part went through is already destroyed there anyway. Since that's the case, I'd take a gas welding torch (rosebud welding tip, not a cutting tip), and heat the area you need to machine to a dull red, then bury it in sand and leave it overnight to cool.

That'll take out whatever hardness the weld had from cooling too fast, and should keep the slide from warping too much.

Obviously you'll have to actually check and makes sure it's not warped afterwards though, don't just assume it's OK.

If the slide is 4140 or a similar alloy, it should be hard enough and strong enough in it's dead soft condition to do it's job, but you can always have the heat treatment redone if you feel it must be normalized (full hard would be way too hard IMO).

I dunno what standard gunsmith practice is when dealing with welding on a slide or frame, but I can't imagine how annealing the part is any worse than having part of it half hard/normalized (the original condition), part of it dead soft (the HAZ of the weld), and part of it full hard (the weld bead itself). The stresses created by that kind of situation would be just as bad or worse than having the whole part be soft.

And honestly, when you're talking about 4140, "dead soft" isn't all that soft (~200 Brinell). Condition "N" (normalized/half hard) 4140 has a hardness of ~300 Brinell, while full hard has a hardness of ~500 Brinell (which is too hard for the beating a firearm takes IMO, but some places might go that far, I dunno for sure). The tensile strength of annealed 4140 is ~90 KSI, while half hard is ~150 KSI.

In a low-ish stress area like where a front sight dovetail goes, I wouldn't think you'd be in much trouble with the annealed condition.

But like I said, I'm not a pro, I just have a pretty good idea how things work. YMMV.

EDIT: HA! PistolWrench snuck one in on me while I was typing. Glad to see I wasn't FOS. lol
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Last edited by LogicGS; 05-12-2008 at 12:20 AM.
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