I recently received a 1615 engine that had been packed away in a box in a garage for the past 45 years. It still runs and I’m cleaning it up. It had not been treated well in it’s day and I need to replace the gear assy links on both sides. Part of this is connected by the valve gear screw. The head is snapped off of one of these. It’s a small screw…just larger than 1/16 inch. Any advice on getting this out? The snapped off head does not stick out at all so there is nothing to grab on to. I started to drill it out with a 1/16 bit but could not keep it on center and it started to drill out the threads …so I’ll stopped. Looking for some good guidance here. If drilling is my only course of action then I’ll probably need some advice on re-threading and repair as well.
I have had luck with Jim’s suggestion getting broken off side rod screws out of drivers and getting trailing truck mounting screws out of loco frames even when they were broken at or below the surface. I have some smallish angled and pointed chisels I use to back the offending screw remains out. It works and has many times when I thought for sure I would need to drill. Now if the area is really mangled or you already started drilling you might have to drill all the way, but I would try to work that little guy out first.
Another trick if you have any room at all is to use a Dremel and small cut off wheel to cut a slot in the remains for a screw driver. This works sometimes too but can cause damage to surrounding areas.
If its the screw I think it is also see if you can get at it from the back side and work it out that way any damage will not be seen.
If your unable to get the screw out by any of the methods mentioned your last try could be your local machine shop. Ask them if they have a EDM machine. That can electrically burn it out and leave the thread intact.
I have done a couple that were broken off below the surface. The trick is to remove the wheel and drill it out from the back. If you can, get a left hand drill it may even back out without “drilling”.
This is the stuck screw. It has 36 thread. To remove just cut the line with a cutting wheel.Split if you have to to remove. Use a 4 40 screw to replace with a nut inthe back. You couldcut the hole piece off and replace with a threaded brass piece. 36 thread is not that common but you will need a tap if you get a replacement screw.
Whenever you first remove a screw it is wise to determine how Stuck it is. If the head is showing damage it is time to use a liquid penetrant or a little heat. Ten to 15 seconds with a torch does wonders but may effect the condition of the piece. This screw is so exposed it wouldn’t take much. The trick is to give time for the heat to work. Something to keep in mind. Working on old - new trains it’s always that first time to remove a screw.
Try dropping some penetrating oil on it and let it work it’s way down for awhile ( I’m talking days) then try using a pick to back the screw out. If you need to put a little heat on it I would try to use a pencil type soldering iron and place it on the screw, that might keep most of the heat on the screw.
I recommend a drop of oil or a dab of grease on every screw to make sure it comes out 30 years from now. I do this for bolts on cars I am working on, and never have a problem removing the bolts at a later time.
I’ve tried a variety of these techniques…starting with least destructive…and still have the snapped off bolt. So, I drilled it out with a 1/16 bit. Trouble is that it was not as clean and controlled as I would have liked and now I have most of the hole and threads damaged. Here’s what I plan to do…stop me if you have a better idea. I will fill the drilled out hole with something like J B Weld (cold weld stuff) and then re-tap the hole. I believe this is a 4-36 thread (just have to find a 4-36 tap)
Does anyone know if there is an equivalent to the 1666E-14 screw that is a 4-40 thread?
Watch out–I think your screw is a 1666E-15. A 1666E-14 is a “truck stud rivet”.
You can get the replacement screw cheaply enough. As long as you’re going to fill the hole with epoxy or whatever, why not skip tapping, put something on the replacement as an attempt at a mold release, and just epoxy the thing in. If it doesn’t release after it sets up, you can always drill it out again when you need to; but, in the meantime, you’ve got a functional screw.
Here’s a link to a thread in which the simple “cast-new-threads” technique that Bob mentions is explained in excruciating detail. It really, really works!
It’s it’s easy, inexpensive and reversible, in the event you find a way to botch it.
In this case, just remember to put a temporary patch (e.g. tape) on the bottom of the hole to stop the epoxy from dripping where you don’t want it; and take care to keep the screw centered and vertical while the epoxy is curing.
Given that this goes into the side of the metal engine housing…should I be concerned about which epoxy to use? I mentioned j b weld only because someone mentioned that to me…is there something else that may be easier to work with?
If you’re asking me, I have a few more tips that might be of interest to you, but I don’t know of any two-part epoxy that is easier to use than J-B Weld.
OK. More or less at random and definitely not in order:
Use normal “'24-hour” cure rather than “fast cure” epoxy; solid “color” rather than clear; use a bit of nail-polish remover (acetone) to clean surfaces before applying epoxy and to clean up; measure out “putty” first, replace cap and set down well away from hardener; then open hardener, measure out correct amount, replace cap and mix very well. In other words, don’t let the hardener get near the open tube of putty. Work in a well-ventilated area.
Have everything ready to go – you only have a short working time even with the “24-hour cure” types. For nice crisp threads you want the stuff to be as liquid as possible. It will never be more liquid than it is immediately after mixing.
After it has begun to set-up you can speed the curing time by applying a little heat, such as from a nearby lamp. I prefer a natural, full cure at room temperature.
Just as you would with paint, mask off all parts of the loco that you don’t want epoxy to find it’s way into.
Unless I have to build a “dam” of some sort, all I use is a popsicle stick, tooth pick, a little masking tape, and a bottle cap to mix in. Never try to do the mixing in the hole that is being repaired.Your biggest problem, as I see it, is to keep the screw centered in the hole while the cure takes place. You may have to get a bit creative. Perhaps you can use something like a very thin washer that you can place over the hole and hold with tape. If you make a thin cardboard washer you can tape it in place temporarily and sand it off later. Some folks have even used thread. Depending on how buggered or oversize the hole is, you may have to solve this
They make them as small as number 1. However, they are made only in UNC and UNF thread pitches; so, while you can get 4-40 and 4-48, you can’t get 4-36. I imagine that you could stretch a 4-40 coil to serve for 4-36; but you can’t get the special outsized tap that you would need to make the hole for it:
One of my favorite repairs is to drill and tap the ruined hole to a larger (conventional) size, then put in a piece of a screw, preferably brass for its machinability, and drill and tap that for the original screw. This would still require having a 4-36 tap; but those do exist:
It’s not clear in this case whether there is enough meat around the ruined hole to do it this way, since you need a significantly larger hole than a Heli-Coil requires.
Epoxy threads should hold the piece in. To keep it simple, just epoxy the screw in. attached and ready to go. I do not think that taping a small hole will hold enough epoxy to keep its form. Another way is to epoxy a nut on the back if you use a longer screw.
When I fix tender screw holes I remove the old post and replace it with a block of epoxy.
If you are determined to go with an original 4 -36 and have a nut that fits.I would shorten the tube (cut from the back)and epoxy the nut on the back.
