I've never had much luck using some of the traditional methods for repairing damaged threads in my projects. For various reasons these techniques may not be workable solutions. The thread may be too damaged to "clean up" by running the matching size and pitch tap through. Drilling and tapping to the next larger size screw may not be an option for mechanical or aesthetic reasons. Jamming in a screw of a different size or pitch or squeezing one of the thread "repair" compounds into the hole won't give you the fit and strength you might need.
My favorite option, by far, is to install a stainless steel insert into the hole that will give me EXACTLY the same size thread as the original, damaged thread. I can the use precisely the same machine screw as I had used originally. The inserts, tiny coils of stainless steel, can also be used right from the get go to add strong threads to parts made of softer materials like aluminum or even plastic.
I'll show you how to properly install one of these inserts in the main workshop at TechShop Detroit. You buy a thread repair insert kit or use the basic tools available at TechShop. In either case the drill press in the Metal Shop at TechShop is very useful for accurately drilling/enlarging the holes you need to make in your part to install these inserts.
Step 1: Gather the Tools
In the first photo you'll see my aluminum block with damaged thread. The size of the threaded hole is (was) for a 10-32 machine screw and I'd like to keep it that way!
Pictured below you'll see the kit of stuff you'll need to pull together to accomplish the repair. This consists of:
-The stainless steel threaded insert, size 10-32
-A drill to enlarge the existing damaged hole
-The correctly sized tap to thread the hole to accept the threaded insert
-The special tool needed to install the insert (comes with the insert kit)
-A knock out bar to remove the tang on the insert after it is installed (more on that later)
-The part with damaged hole (but of course)
-The 10-32 screw I intend to use in the repaired hole and a screw driver to drive it in
And If I'm going to make a hole from scratch that I intend to install steel threads in from the very beginning:
-A center punch to mark my hole postion
-a hammer to give the punch a light, firm tap