Wandering base

[Brad]

Shooting my CZ 75 with a Vortex Venom today and noticed my sight base had shifted way over.

Base has a set screw that goes thru the dovetail to help hold it in place. That screw was snug and had blue Loctite. I was afraid of snugging it more as those little hex keys are easy to strip.

Going forward I am thinking some green Loctite on the dovetail? Let it wick in and help hold things tight.

This is after about 3-400 rounds.

 

[Ian]

If the screw didn't back off then some metal moved somewhere. Take it off and have a look first to see what happened. The dovetail may have stretched. Soldering iron on the screw will help defeat the blue threadlocker.

 

[462]

Sheared screw?

 

[Brad]

Set screw slide across the dovetail. I think the dovetail is a little loose and that is letting the movement overcome the screw.
I will clean it well and reinstall with a little Loctite in the dovetail to take up some of the slack and help hold things in place.

I love the set screw, I wish it was a bit larger to give more bite.

I will say that i really like this little sight. Makes shooting the pistol far more enjoyable.

 

[smokeywolf]

Just curious Brad. What is the width of that track created by the set screw? As measured with your caliper points.

 

[Brad]

I have it all back together so I can’t measure it?

Looks to be a #4 set screw so that track is pretty narrow. Might be .075?

 

[Ian]

You could also set it up in your mill and put a little dimple for the grub screw to grab.

 

[smokeywolf]

You have a good eye. Minor dia. of a 4-48 is .086

 

[smokeywolf]

You could also set it up in your mill and put a little dimple for the grub screw to grab.

Kind of what I was thinking.

 

[Charles Graff]

For sights in a dovetail that want to move, I have taken a center punch to the bottom of the dovetail and raised some dimples to tighten the sight up. Worked every time.

 

[Brad]

I never thought of that. Makes complete sense. I may just do it.

How deep? Maybe .040? I don’t want to take a chance of breaking thru to the hole for the firing pin. I may have some drawing and measuring to do.

 

[462]

Base has a set screw that goes thru the dovetail to help hold it in place.

Had me thinking the screw was threaded into the dovetail. Thus my comment about a sheared screw.

You could also set it up in your mill and put a little dimple for the grub screw to grab.

I was thinking this, too.

 

[Ian]

.025" deep at the edge of the grub screw should be plenty.

 

[fiver]

about 2-3 turns with a good drill bit should be enough.
I use a countersink on my bench for my 505 scale, the foot goes in the dimple and is repeatable, this is the same principle.

 

[Charles Graff]

I never thought of that. Makes complete sense. I may just do it.

How deep? Maybe .040? I don’t want to take a chance of breaking thru to the hole for the firing pin. I may have some drawing and measuring to do.

I never measured the depth. A slide is pretty hard and I doubt there is any chance of penetrating it with a center punch. Just raise a dozen dimples across the bottom of the dovetail. Dovetails are tapered and folks that drive a sight in or out from the wrong direction often screw up and loosen the dovetail. This is an old gunsmithing fix. Before there was thread locking stuff, things still needed to be done. Iodine on a screw would rust it in place....works.

 

[Ian]

Charles, the reflex sight base is an intentional slip-fit with a locking grub screw. Dimpling the bottom of tue dovetail may make it snug but if it walked out dragging the grub screw tip so it scraped a groove in the slide, I doubt your recommendation for tightening a loose sight is going to help. When the grub screw is tightened, it will pull away from the bottom anyway, taking load off of any dimples. Besides, if the slide can be dimpled with a punch, it can be drilled. If too hard to drill, a diamond-coated burr and some TLC will burn right through it.

 

[Charles Graff]

Charles, the reflex sight base is an intentional slip-fit with a locking grub screw. Dimpling the bottom of tue dovetail may make it snug but if it walked out dragging the grub screw tip so it scraped a groove in the slide, I doubt your recommendation for tightening a loose sight is going to help. When the grub screw is tightened, it will pull away from the bottom anyway, taking load off of any dimples. Besides, if the slide can be dimpled with a punch, it can be drilled. If too hard to drill, a diamond-coated burr and some TLC will burn right through it.

I have never seen a reflex sight or know what a grub screw is. You boys have fun playing with this new fangled stuff. Don't bother trying to educate me, because I really don't feel a need to update on this stuff. All I know is old stuff such as sights in dovetails. I have also peened the top lips of a dovetail to tighten up the slot. But that might show, that is why I refer the center punch. I have tightened up sights in dovetails that have not moved in with thousands of rounds.

 

[david s]

I forget exactly what the CZ 75 finish is but isn't it some kind of polymer? Generally the CZ finish is thicker than most common finishes. Your second photo almost looks like when you tightened the grub screw it pushed thru the CZ finish and then began to peel to the right. Not wanting to strip the set screw you may have only bitten into the finish instead of the slides steel. Any way my best WAG.

 

[Brad]

The polymer finish is a potential issue. I thought the same thing Allen.

I will likely take it apart and look at drilling a little dimple for the grub screw to lock into. To me that is the most elegant solution.

 

[Brad]

Took it all apart tonight.
Set in mill, spot drilled very shallow, and drilled a very shallow, maybe .050 Deep hole at .070.
PuttiIng it together I could see that the hole lined up well with the threaded hole for the grub screw. A little Loctite and it was all together again. Maybe took 15 minutes?