Filling and retapping 00-90 holes?

[Lemosteam]

^^^^^ Agreed- is the hole blind?

[mike_lawyer]

This hole is in a Kato Mikado frame.  It is on my 2-10-0 project, the screw is used to hold styrene to the metal frame.  I had to redo one of the styrene blocks, and the hole got stripped in the process.  I will take a photo later and upload it.

[mmagliaro]

Oh.. I think I see.  Those styrene blocks that carry your 5th driver?   If that's the case, yeah, can you just put a 00-90 nut on the other side of the hole, and go all the way through with a long screw?  Or as others suggested, grind away or drill in from the other side, get a nut back there, and then use the longer screw?  Another thing to consider if you are putting a nut in there... get some stainless 00-90 nuts and screws.  They will be much less prone to stripping than the brass.

Incidentally, I had this problem with some of the holes on the gear coverplate on my brass 0-6-0 project.  I had those screws in and out so many times during development that the threads on some of the holes got really worn out.  Since I started with M1.0 (much smaller than 00-90), I was able to just bump up to M1.2 on the troublesome ones - retap and put in a new screw.

When you are tight on space - go metric.  When I did my original I1s project, I was still in an "all USA thread sizes" mind set.  But believe me, those M1.0 screws can really help by fitting into places where 00-90 can't , or by fitting in without drilling holes that dangerously thin out the metal frame.

[mike_lawyer]

Oh.. I think I see.  Those styrene blocks that carry your 5th driver?   If that's the case, yeah, can you just put a 00-90 nut on the other side of the hole, and go all the way through with a long screw?  Or as others suggested, grind away or drill in from the other side, get a nut back there, and then use the longer screw?  Another thing to consider if you are putting a nut in there... get some stainless 00-90 nuts and screws.  They will be much less prone to stripping than the brass.

Incidentally, I had this problem with some of the holes on the gear coverplate on my brass 0-6-0 project.  I had those screws in and out so many times during development that the threads on some of the holes got really worn out.  Since I started with M1.0 (much smaller than 00-90), I was able to just bump up to M1.2 on the troublesome ones - retap and put in a new screw.

When you are tight on space - go metric.  When I did my original I1s project, I was still in an "all USA thread sizes" mind set.  But believe me, those M1.0 screws can really help by fitting into places where 00-90 can't , or by fitting in without drilling holes that dangerously thin out the metal frame.

Max -

Thanks for the great info as always.  Yes, it is for the styrene blocks for the fifth driver.  I have been trying to make the cover plate, and all the times I have had to take it on and off have worn out the threads.  Also, I had to redo one of the styrene blocks, so the threads may have gotten worn down by that as well.

I will have to check out the stainless steel nut idea.  It might work out here.  I suppose if there is a metric size that is just a hair larger than 00-90, I could also go that route by drilling and tapping a new hole.

[u18b]

I concur with Max.

I use M1.4 all the time.  It is a common screw in brass locos.
It would be "the next size up". (should that be the way you want to go.)

Screw and taps are readily available online.

[mike_lawyer]

Yes, I was looking at M1.4 screws, that looks like the next size up and not much bigger than 00-90.  I might have to try that out.

[mmagliaro]

And if you want to go the other way, with a SMALLER screw and a nut embedded in the frame, you can go all the way down
to M0.8  (yes, smaller than M1)...
https://minitaps.com/m-8-80-unm-thread/

I won't kid ya.  Stuff this small isn't easy to work with, but it sure does the trick when you need a nut and bolt in a tiny space.

[narrowminded]

Just got this.  Sounds like it's covered.   It often depends on what the situation is including materials, space, depth, purpose, and etc.  Here are some rambling thoughts on the general subject of shade tree thread repairs.

In plastic I've used ABS filings dissolved in acetone or MEK and applied in the hole with a tiny paint brush to build up the hole.  Allow to cure at least 24 hours and tap new.   

I've used thin epoxy and even super glue in a drilled hole in wood paneling or drywall to "harden" the hole.  Thread in the screw first to make a thread but don't tighten it at all.  Just make the thread.  Remove the screw and soak the hole with the glue.  The screw can also be reinserted if there is concern about holding the shape.  If reinserted before the glue is cured, wax the threads by rubbing them on a candle stub to act as a mold release.  This has become my go to method for hanging bathroom fixtures and the like.  Easy to fix a small hole later, too.

In aluminum with more than a diameter engagement, I've just filled a hole with epoxy and inserted the screw I was going to use, first waxing the threads by rubbing them on a candle stub to act as a mold release.  Let the stuff start setting up, remove the screw, give it 24 hours or so to cure, and then have at it.  If there are a couple of diameters engagement these mentioned methods can actually be pretty decent.

Also, if there's room for a stud and nut, just epoxy a "stud" fashioned from a long screw or a piece of all thread into the stripped hole.  More than one diameter engagement is always nice to see for this but a stripped hole already has the roughened and grooved surface that epoxy likes to have for a strong joint and the thread is also pretty ideal for epoxy to grip so this can be a pretty effective repair. 

With room and a lathe, metal sleeves are always a possibility.  They can be soldered in place or if room, shouldered.  Shouldered can also be glued or loctited to help hold in place.  The wall can be pretty thin if needed.  This is why the answer to this question is always, "it depends".   

[Steveruger45]

Yep, as Mark says, the situation and your tools really dictates the method.
Just to add another arrow to the quiver and one I have used when the situation allowed it is to insert a nut in the material that needed thread repair.  Just drill out the metal material a tad under size for the OD of the nut most of the way through from the back, you can relieve the nut edges to suit the drill, to get a mechanical interference fit and press the nut in.   No soldering, no glue needed.