Bubba strikes again - Super Blackhawk rear sight restoration, need help please

[David2011]

A friend brought his Super Blackhawk to me. The previous owner had installed a hideous scope mount and drilled out the original sight mounting hole to tap it to 8-40. The original hole was 6-48. I drilled out an 8-40 plug screw to thread it to 6-48 but the remaining wall thickness is scary thin. One idea I had was to secure the 8-40 plug in place with green loctite before tapping it but I have concerns about that not holding up. Another idea was to drill the 8-40 hole out to 10-32 and securing a 10-32 plug in place with red loctite after tapping it to 6-48. Physically I know that will work but I have concerns about weakening the top strap. There are the ears of the sight mounting slot on either side of the sight mounting hole so maybe there is plenty of metal remaining even after tapping to 10-32.

Has anyone been there? Any ideas or suggestions?

[Mica_Hiebert]

Weld it, grind, drill, tap, reblue.

[David2011]

Weld it, grind, drill, tap, reblue.

While I agree that is a good and proper solution it is not in the customer's budget.

[Der Gebirgsjager]

How's about making a "U" shaped cap plate out of sheet metal to go over the top of the backstrap, then drilling and tapping that over the original hole?

[David2011]

There's really not much room to add another layer of metal. The sight fills the channel with only thousandths of extra room. I'm leaning at this point toward soldering in the 8-40 screw that has already been drilled rather than using green Loctite. I could safely tap the screw once it's soldered in and not have to worry about the Loctite failing later.

[egg250]

I believe you'd be good with just the Loctite. The 8-40 screw is filler and is likely just as hard as the frame. With the frame supporting the drilled out 8-40 screw, there is plenty of support.

[pietro]

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Since the light weight of the rear sight is unlikely to cause any holding issues, I'd go with the 8-40 plug screw, D/T'd 6-48 & everything Loc-Tited.


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[Jim_P]

How about Red Locktite'n in a 8-40 set screw. Once set with the Locktite, drill and tap for the 6-48. Should be easier to get all centered up.

[RED333]

8/40 plug drilled but not taped and a bit longer than the hole is deep. Green Locktite and
Swag the plug or pein the plug so it wont get loose. Then tap to correct thread and pitch.

[frkelly74]

Can you drill out the sight for the bigger screw? I would tend to be cutting on the cheaper part if possible.

[runfiverun]

I'm with frank on this one.
it would be a simple drill and countersink.
I don't think they use a click stop on the sights.

[WJP]

I'd look for a screw that would fit the rear sight or open it up to take the 8-40 as well.

[David2011]

Hmmm. Made a post last night that isn't here. The major diameter of the 6-48 would cut into the minor diameter of the 8-40 so that's not going to work. Got to drill and tap to 10-32. I'll make a tight fitting plug from tool steel, mill it flush and solder it in. That can be tapped back to the original 6-48 and will be permanent.

Both the sight and screw have components of the click stops built in so it's going to be best to keep them original.

[2152hq]

Drill the 8-40 threaded hole out to just clear the threads away. No larger is needed.
Then do as Red333 suggests above and insert a plug into that hole and peen it into place.
A very slight counterbore on the bottom of the top-strap courtesy your favorite Dremel tool and a similar but a little deeper and cleanly cut squared corner counter bore on top will not only secure the plug in place but make the repair invisable after filing it down.

A touch of Lok-tite can be used if you want but avoid it coming to the edges of the counterbores and leaving a line there to give away the repair,,that's if you are concerned about the looks.
The top side will be underneath the sight anyway and the under side of the top strap is just that,,on the bottom.

Once in place, that plug can be easily D&T'd to 6-48. With the old 8-40 threads removed from the hole, the new dia plug gives you more than enough mat'l to cut new threads into.

Just the way I'd do it.

[W.R.Buchanan]

Dave: if the hole is blind, I'd drill it out and "press fit" a plug into it and then D&T it and be done with it.

IF the hole is reamed after you drill it out then you can predictably make a plug that is .001-.002 bigger and press it in and it will stay. a 6-48 tap doesn't impart to much thrust on the work piece due to the relatively small size of the thread profile so the press fit will hold the plug in place.

Randy

[David2011]

Randy,

It's threaded all the way through the top strap.

Does that change your ideas? The idea to peen a plug in place isn't bad but there's not a lot of space inside the sight slot in the frame for a hammer nor inside the cylinder aperture for a buck due to the proximity of the recoil shield. I don't want to make it worse.

[W.R.Buchanan]

Dave: if it is all the way thru you would just make the plug longer, and push it in until it was flush with the inside. Then cut it off and file it even with the top strap.

I got my gun out and they definitely tapped that hole all the way thru. Reason probably being not wanting to stop the tap in the small radius at the back of the cylinder opening. Opening it up will not work as the plug would engage that radius and would a PITA to pull off the first time. Obviously you only get one chance.

Next suggestion is see if someone makes a 6-48 Helicoil. This would be the easiest and probably best fix as the hole would get opened up for the Helicoil which would fix the stripped threads and then return the hole to the previous standard size after the insert was installed.

Problem with this is finding a 6-48 Helicoil and tap. Looking now and will get back to you.

Randy

[daniel lawecki]

Emhart Teknologies has helicoil that will work

[David2011]

Life got in the way in a big way late last year. Situation is resolved; I'm now retired. I was living and working away from home and only at the house from late Friday evenings until Sunday afternoons. Now I'm in the shop almost every day.

I fixed the Blackhawk. Living in an area where anything better than Home Depot metals have to be ordered, I decided to use a 1/4x20 socket head capscrew to make the bushing. I started by cutting the head off with a cutoff wheel and facing it. The next step was to drill and tap it to 6-48. I wanted to minimize the losses if the tap broke. Fortunately a new Brownell's tap threaded it easily. Next the OD was turned to 0.190" (factory 10-32 threads measured .187") and Blue Dykem put on it. I stoned the edges of a hand made HSS threading tool to freshen it up for these small threads. It didn't take long to cut the threads. The tool holder was coming within about 3/16" of the chuck on each pass. Nerve wracking. I made a thread tester with the tap that would be used to thread the Ruger's backstrap. The threads engaged snugly as intended. I removed the workpiece and cut the bushing off. It was threaded it onto a 6-48 screw and held in the parrot vise while it was filed to the correct length of .130". The same 6-48 screw was used an an installation tool. Blue Locktite was (probably unnecessarily) applied as insurance. The fit was VERY tight as I had hoped. It was so tight that I put a new 6-48 screw in for the last turn. The edge was still a little proud so I cut it off with a center drill held in a chuck from a discarded drill, like a large pin vise. I have no concerns about the bushing backing out. The new rear sight was installed without issue.

[pietro]

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All's well, that ends well - an elegant solution !

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