Removing Coil-type Threaded Inserts

4375 Views 10 Replies 7 Participants Last post by RickKr, Feb 27, 2019

RickKr

Discussion Starter · Feb 26, 2019

I've been using the coil-type threaded inserts for a number of years. I tried the large brass screw in type but had too much trouble with the wood splitting or it was just too hard to drive them in (was using oak at the time). Mostly, I've been using 1/4-20 and recently found a local source for inserts in various sizes from 1/4"-3/4" in 1/8" increments.

For a birthday gift for my daughter, I recently made a "twined rag rug" loom where I made a framework from 3/4" x 2" pine and used 3/4" threaded inserts for the major corner connections. I had to place the inserts into the end-grain of the shorter cross members at the top and bottom.

I had no problems at that time getting the holes located and centered, so I was surprised when I did have problems when recently making one more cross member. The holes were in the right place laterally but were off-center in the thickness. Very disappointing. I could have let it go as it would probably never be noticed, but I'd know.

So, in an attempt to fix the off-center holes, I needed to extract the threaded inserts, which I'd never done before and wasn't sure if it could even be done. I thought of trying some easy-out type broken screw extractors, but was not at all sure it would work. I thought the extractor would just expand the insert and prevent if from rotating. Not so, they came out quite easily. In the second photo below, you can see how much the holes were off-center.

The plan was to plug the off-center holes and redrill/tap them for new inserts. I was much more careful with my setup to be sure the holes were drilled on the centerline. But my best plans were foiled by my use of hardwood dowels for plugs. The center-drilling went Ok, but once I started drilling the 17/64" hole for the tap, the drill walked way off, finding easier going in the pine.

No real surprise, but frustrating enough that I'm going to give up on fixing this stick and re-make another and drill/tap those holes in fresh wood.

Rick

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Nickp

· #2 · Feb 26, 2019

Nice thought for getting the insert out...

Heli-Coil makes a tool for gettin' those babies out...same principle as the extractor you used but has sharper edges for biting into the coil top thread...

https://www.mscdirect.com/browse/tn...LdrBsRoNGHay4uWDMNnKw7TAXm-AUkaEaAgorEALw_wcB

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sreilly

· #3 · Feb 27, 2019

Good tip Nick, I hadn't seen these before and I'm sure it will happen to me sooner than later. I'm guessing the bit walked due to the differences in the hardness of the woods?

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gmercer_48083

· #4 · Feb 27, 2019

Rick, This seems like a good tip. I have made various hand tools that require the threaded inserts, and sometimes the tool needs to be bulkier because the brass inserts are thicker in diameter. Using Heli coils seems like the solution. Thanks for the tip.

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roxanne562001

· #5 · Feb 27, 2019

That is a great Idea using helicoils for thread inserts in wood. I have been wood and metal working for years and never would have thought of that. Thanks for the tip.

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ebill

· #6 · Feb 27, 2019

RickKr said:
....... I'm going to give up on fixing this stick and re-make another and drill/tap those holes in fresh wood.

Rick

- its good that you were able to successfully savage the inserts. Even better that you hit upon the best solution ... make a new piece. I have spent considerable time 'futzing' with pieces for different reasons only to come to that same conclusion in the end.

- ebill

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Cherryville Chuck

· #7 · Feb 27, 2019

It sounds like you are marking and drilling holes by hand Rick and that always leads to disappointment. If you throw together a jig using these: Bushings and Inserts - Lee Valley Tools you'll be able to land where you want. You could make a jig in 10 minutes out of scrap that guarantees you will line up one set of holes with another. The only trick to the jigs is adding stops to the edges so that they register exactly where you want the holes. In other words you put the stops on the jig so that the holes are located at the right distance from the end and/or an edge. Look at the picture carefully in the ad and you'll start getting ideas how to use them. These bushings will also help keep you drilling straight in a case like your repair. You need a 5/8" hole for the inserts and then you screw the size bushing in you want to use. About a $75 investment will buy enough inserts and bushings for most jobs you want to do.

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Nickp

· #8 · Feb 27, 2019

sreilly said:
Good tip Nick, I hadn't seen these before and I'm sure it will happen to me sooner than later. I'm guessing the bit walked due to the differences in the hardness of the woods?

Steve...thanks...however, I will need to defer to Rick regarding how the drilling did not go as planned. There are too many variables for me to offer any conjecture. As you might already know, drilling into end grain takes on its own life.

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RickKr

Discussion Starter · #9 · Feb 27, 2019

ebill said:
- its good that you were able to successfully savage the inserts. Even better that you hit upon the best solution ... make a new piece. I have spent considerable time 'futzing' with pieces for different reasons only to come to that same conclusion in the end.

- ebill

Actually, the objective was to remove the inserts only. Once installed and the little "driving tang" at the bottom of the insert is broken off, there is no way (that I am aware of, but I haven't thought about it) to drive the insert, further in the original hole or again into a different hole.

Yes, "futzing" can be a major waste, but it was worth a try and I learned something about (removing) the inserts. I have moved on from this with making a new stick in which I'll have to place four new inserts.

Rick

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RickKr

Discussion Starter · #10 · Feb 27, 2019

sreilly said:
...snip...
I'm guessing the bit walked due to the differences in the hardness of the woods?

Yes, they did walk due to the greater hardness of the plugs. My bad, as I usually work a little smarter than this. Two things, at least, that I should have done differently:

1) Drilled the holes out larger and used a dowel diameter that placed the correctly located hole, wholly within the plug wood, and

2) Started small and work my way out in 2-3 increments so the "path of least resistance", which a drill will follow, was more controlling than the difference in the wood density/resistance.

I do 2) frequently, but was lazy I guess, even though I have the dowels that would have made 1) easy. I think I just didn't want to drill a large enough hole to start with.

Nickp said:
Steve...thanks...however, I will need to defer to Rick regarding how the drilling did not go as planned. There are too many variables for me to offer any conjecture. As you might already know, drilling into end grain takes on its own life.

Yes, drilling into end grain presents its own challenges. I used a centering/squaring drilling fixture, where there is a platform for holding the drill square and legs that can be extended down the board and when each are held tight against the side of the board, centers the drill.

To widen the base against which the squaring platform rests, to provide a broader surface to guide the squaring, I placed boards of the same thicknesses on either side of the stick I was drilling (see photos above). This had worked well in the past and did so when I drilled the previous ten end holes. I think I got careless and didn't hold one of the legs firmly against the guide board, probably the one underneath where I couldn't see it.

I think this effort of plugging and redrilling was doomed to failure due to my using a plug that wasn't wide enough so the new hole was entirely encompassed by the dowel.

I've used this fixture for going on 40 years without this much trouble. I have another, more modern one, that can tilt and has recoil springs. I don't like it and don't use it. This old one works well, but I did have to remake the shaft after it got bent... somehow... :surprise:

Rick

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RickKr

Discussion Starter · #11 · Feb 27, 2019

Cherryville Chuck said:
It sounds like you are marking and drilling holes by hand Rick and that always leads to disappointment. If you throw together a jig using these: Bushings and Inserts - Lee Valley Tools you'll be able to land where you want. You could make a jig in 10 minutes out of scrap that guarantees you will line up one set of holes with another. The only trick to the jigs is adding stops to the edges so that they register exactly where you want the holes. In other words you put the stops on the jig so that the holes are located at the right distance from the end and/or an edge. Look at the picture carefully in the ad and you'll start getting ideas how to use them. These bushings will also help keep you drilling straight in a case like your repair. You need a 5/8" hole for the inserts and then you screw the size bushing in you want to use. About a $75 investment will buy enough inserts and bushings for most jobs you want to do.

Thanks for the link on the drill bushings, Chuck. I'll keep it in mind.

Having worked in my father's machine shop in my youth, I am familiar with drill bushings/jigs. I used jigs my father made for drilling thousands of holes in parts we were making. I never fabricated the jigs, but I watched/helped him do it.

I have been metal working/machining as a hobby for almost 20 years. I have a vertical knee mill with three axis DRO that I use extensively as a very accurate drill press, in both metal and wood. When I cannot use the mill for drilling, such as these end grain holes, I do careful layout and in this case, used the squaring/centering fixture mentioned above. I've mentioned some reasons why it didn't work out this time.

When making a drilling jig, as you describe, there is a trade-off for the the time it takes to make the jig(s) versus what it takes to just do the job by other means. In this case, even having some bushings on hand, and having the drilling fixture that has worked so well in the past, I believe I would have elected not to make the bushing-ed jig.

Thanks,

Rick

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Removing Coil-type Threaded Inserts

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