Tap or bolt removal

Date 04-13-2011 04:33

Hi folks, this is somewhat of a revisitation of an old thread, yet, the opportunity arose to get some new pictures and an example of broken tap removal so I figured it would be worth throwing it out there again.
The folks in the machine shop often present challenges for us over in the weld shop. Intended or not, these challenges are good for learning on the parts of both the machinists and the welders. One of the items that the machinists are given to accomplish involves layout, drilling, reaming, chamfering, and tapping a rectangular chunk of cold-rolled stock. In this particular instance and for whatever reason, the student decided to try power tapping a blind hole as if it was a through one.
Obviously, the results were far from nice or successful. The tap broke and shattered leaving remants of the tip of the tap in the hole and wedged up rather tightly. For this particular challenge the GTAW process was chosen to tackle the removal task and stainless filler was the choice for build-up purposes. I have generally found that stainless filler works really well for both avoiding excessive porosity while welding through tapping fluids/oils and providing a fairly resilient build-up that can withstand a fair amount of torque without re-breaking. Sometimes, however, this process requires multiple applications to come to a successful conclusion, you might only get a small part of the broken tap each time you attempt it. Bolts can be removed in a similar fashion using the same procedure. I know there are many different ways that others approach this situation and as usual I would hope to hear of those(complete with pictures of course) and narratives for the specific steps. Best regards, Allan

By TimGary (****)

Date 04-13-2011 20:16

Great info aevald, especially for taps that are really stuck in there.

Please see the following link for special tools made for extracting broken taps. They work fairly well, and come in mulitple sizes shapes to fit most taps.

http://www.waltontools.com/products/extractr.htm

Tim

By 99205

Date 04-13-2011 20:55 Edited 04-13-2011 21:05

Another way is to use a plasma cutter. I set the plasma orifice slightly above and centered above the broken tap or screw and trigger the handle in short bursts. I do that until I've burned through and then use a small pick to pop out the pieces leaving the threads untouched. Works well all the way down to 1/8 inch hole but your aim needs to be pretty good at that size. Of course this doesn't work well on stud holes.

By aevald

Date 04-13-2011 21:04

Hello 99205, How about blind holes? Have you used it in that situation as well or only on through holes? I'm just curious. Thanks and regards, Allan

By 99205

Date 04-13-2011 21:06

just edited my post after I thought about that.

By aevald

Date 04-13-2011 21:07

Hello Tim, thanks for the reply. I have seen those and read their description, but have never used one. In many cases I'm sure they would work rather nicely. Best regards, Allan

By DaveBoyer (*****)

Date 04-14-2011 04:17

I have used those, they work OK on the ones that will come out easily.

When a tap is in deep, bound against the bottom of the hole and broken off, often it isn't a clean break, the tap has other fractures that cause the pieces to wedge in the hole when You try to turn it.

Like any removal process, the smaller the tap, the worse it is.

In the tool & die shops, there is often an EDM machine. These use high frequency electric current to "burn" away the tap. Each spark from the electrode to the tap blows a tiny divot out of the tap when it strikes. The sparks occur at radio frequency [really often] and You can use a copper or brass tube as an electrode, so You don't have as much material to remove. There are some attachments for drill presses to do this, and I have seen a simple home made device, but I don't have a computer link to it. This process works really well, every time.

By welderbrent (*****)

Date 04-13-2011 21:03

Hello Allan,

I know you and I have discussed some of my previous involvement with equipment repairs while up in the great Northwest. I have used several diverse applications of that same process to successfully remove broken taps and bolts. It has been so many years ago that I don't have pics for illustration but they wouldn't really add much to yours.

I have also used GMAW for the welding. When down in the hole a ways you can gently build the bolt or tap back up to the top without sticking anything to the sides of the hole. Then take a nut just the size of the hole and weld through the hole to the shaft. Let it cool a bit then it turns right out.

Usually from the heating and cooling you will get enough shrinkage of the diameter of the bolt or tap that they will turn out fairly easy even if they were in there really tight.

They also make some special electrodes for this procedure but they are really expensive and don't really work much better than 316 Stainless electrodes.

I still like the spray arc GMAW better myself almost all the time.

Have a Great Day, Brent

By aevald

Date 04-13-2011 21:17

Hi Brent, that's kind of why I included "revisited" in the description here. This piece came over to visit the weld shop from the machine shop and I saw an opportunity for a few pictures and some additional conversation to let others know of this sort of thing if they were possibly new to the site. There are certainly any number of methods out there for this sort of challenge and I appreciate anyone who has one of those to share it here. On a slightly different note, I hope things are improving the for you, the family, and everyone else around you. I believe you had mentioned some rather life changing challenges a while back. Best regards, Allan

By welderbrent (*****)

Date 04-14-2011 14:52

Things have smoothed out a litlle. Still rough. Work slow. Oldest son definitely found his niche in ministry and other work 100 miles away so left me without any of the boys at the shop now. Rather difficult trying to keep the shop running in this economy to a level that might make it worthwhile for someone to buy while at the same time trying to keep the new venture in inspecting going to a level where it will support us when I don't have the shop anymore. But the inspections wages won't cover the shop overhead. So right now I am losing money everytime I go do inspections. When Darrell was here running the shop it wasn't a problem. We basically had two separate businesses going. Some things just don't work well together for being diversified.

Thanks for thinking of us. We need all the advice, thoughts, and prayers we can get.

Have a Great Day, Brent

By warmka weld (*)

Date 04-13-2011 23:41

Along the lines of welding a nut to the broken part. I was taught to weld a flat washer to the broken of piece first and the weld a nut to that. Can be difficult to get a weld down through a nut thats only 1/2" or so diameter. Seems to work fairly well.

By welderbrent (*****)

Date 04-14-2011 14:46

Difficult yes. But I've done it on nuts down to 3/8.

The washer is a good idea. Gives some added surface area for a smooth twist as you start the bolt moving. A nut can hang up a little.

Have a Great Day, Brent

By Pat

Date 05-07-2011 01:40

I realize that this post is a little old, but I wanted to say that I have found stainless and 7018 rods to work real well for items that are at, or just below surface. Other than that, I use Messer MG 600 or Excelloy 61 S rods for items 1/8" or more below surface. Granted, there are people on here who are steady enough to use regular rods on things well below the surface, but I am not one of them. I prefer the MG 600 over the Excelloy primarily because of price. Yes, these rods are a little pricey, but sometimes they will save you money.

They have something in the flux that will fill in the threaded area so you do not weld the item to the threads. On holes larger that 3/16" diameter I sometimes insert a piece of copper tube or some other non-ferrite metal so I am sure that I am centered. All is well if you can get by using stainless or 7018 rods, but I like to increase my odds. For those of you that might want to get a few of the special rods to keep handy just in case, US Forge (which is owned by Messer) has a package of rods called "Problem Solver" which I believe is the same as the MG 600 rod. They work just as good.