Repairing stripped thread in brass loco

[nkalanaga]

Actually, Helicoils are made by Stanley Engineered Fastenings, which has factories all over the world.
https://www.stanleyengineeredfastening.com/
https://www.stanleyengineeredfastening.com/fasteners/inserts

[peteski]

Actually, Helicoils are made by Stanley Engineered Fastenings, which has factories all over the world.
https://www.stanleyengineeredfastening.com/
https://www.stanleyengineeredfastening.com/fasteners/inserts

Ok, that makes sense then.  So it appears that the Helicoil domain name is owned by some company in India.  Usually the parent company of some specific brand-name product tries to own the related domain names. Unless that Inidian company is part of Stanley Engineering?

[mmagliaro]

You don't have to use a metric screw just because that's what was in there.     The 0-80 is about .005" bigger than that hole, and 1-72 is .020" bigger than that hole.  I'd just use whatever size I already owned a tap for (and I'm just betting that we Americans have an 0-80 or 1-72 tap, but maybe not a metric one).

I think an 0-80 will work.  You said the original screw was 2mm long, (.078").  At 80 threads per inch, an 0-80 would get you 6 threads in that hole, which is plenty.  A 1-72 would get you 5 or 5-1/2 threads... also plenty.  If it were me, I'd measure and try for the bigger 1-72, if there's enough metal around that hole.

[nkalanaga]

Peteski:  Either one is possible.  Or, maybe, the Indian company is Stanley's importer in India.  Or, Stanley may have registered Helicoil.com, but not .in, and the Indian company grabbed it.  There are a lot of possibilities here.

My former employers website was a .net name.  The same name, with .com, ended up at a porn site.  Oddly, the company name didn't sound like a porn site, but someone had it anyway.  Our main servers had the .com site blocked, just in case some typed wrong.

Internally, we used the company intranet, so there was no problem, but occasionally someone had to go through the public site, for whatever reason, and then we could have issues.

[Sharky_McSharknose]

Thank you for the suggestions, everyone! I think I will try using a 0-80 drill and tap set (Kadee sells such a set.).

[ChristianJDavis1]

When I went home I checked mine to compare. Probably too late to matter, but it does look like you have the screws in the correct places based on what mine looks like.

[learmoia]

When I went home I checked mine to compare. Probably too late to matter, but it does look like you have the screws in the correct places based on what mine looks like.

Damn.. that thing is in rough shape!!

[ChristianJDavis1]

Damn.. that thing is in rough shape!!

I think it looks a lot worse than it really is; paint was put on really thin with what appears to be no primer, so it's been rubbed off over the years in places like the underside. Runs well, and for what I paid for it, I'll take it.

[peteski]

Looks to me more like chemical blackener than paint.  But it is hard to tell in the photo.

[Lemosteam]

Thank you for the suggestions, everyone! I think I will try using a 0-80 drill and tap set (Kadee sells such a set.).

@Sharky_McSharknose ,

Suggest you by two taps.  One to leave as is; with the lead in taper on the end of this tap you are unlikely to get any full depth threads in that shallow of a hole.  Take the second tap and using a cutoff wheel on a Dremel remove the tapered portion entirely, then tip the tap to a 45 degree angle to the side of the cutoff wheel and rotate the tap to grind a small chamfer, slightly below the minor diameter of the tap on the newly cut end.

What you are doing is making a bottoming tap, which will get you full threads nearly to the bottom of the hole, after the first tap is used. there should be enough thread for the bottoming tap to grab and finish the job.

Also, keep in mind that the MT taps are thread forming, not thread cutting and tend to bind in the hole more easily, but the advantage is they are less likely to snap.

[mmagliaro]

Sharky...
It looks from your photo that the hole goes all the way through the frame and there is open space behind it.  Is that correct?  If so, then you needn't worry about needing two taps.   Just make sure you run the MT tap well through the hole so that you get to the non-tapered portion of it in the hole and get fully formed threads.

But if the hole is blocked so the tap is going to "bottom out" in there, then yes, by all means, Lemosteam's observation is spot on.  You will want to get the threads started with a tapered tap, and then finish with the "bottoming" tap to get full threads all the way through.

[Sharky_McSharknose]

The hole does go all the way through.

[Sharky_McSharknose]

I picked up the Kadee 0-80 tap and drill set and some 1/8" brass 0-80 screws at the Amherst show this past weekend. I used them to repair the stripped thread in the frame. The bottom plate is much more secure now. The H10B is not running perfectly as it is a little shaky, but it is running far better than before. It is no longer wobbling and bouncing down the tracks.

Something of note with the Key/Nakamura H10s is the reason why the front frame hole goes all the way through. The bracket for the valve gear screws into the top side of the front frame hole. Luckily, the bracket screw is about the same length as the plate screw, so even though I am using a longer plate screw they still don't touch. I guess I could have used a longer screw of the original thread pitch but frankly I think the new screw was the best way to go.