Broken Tap Advice?

S

scherar

Well-Known Member
I was tapping a tang for mosaic bolsters this morning and broke an 0-80 tap in the hole. Things were going pretty well and I guess my mind started to wander and it broke. Any suggestions on what my options are? My first thought was to drill it out with the next size tap drill for a 1-72 (not as common as 2-56 taps though) tap. Am I on the right track? Will jumping up to the next size drill bit/tap drill through the broken tap without veering on me?

Thanks.
 
Never a fun thing to have to do. But depending on what and how the tap broke there are a few things you can do. As you mentioned drilling it out is one way if it broke off nice and flat you can center punch it and drill it with a carbide drill(a HSS drill will not touch a HSS tap) but a good chance of things walking a bit or you can try and get it to move with a punch and hammer or brake it with a punch and hammer or one of the best ways if it is flush with the top of the part or sticking up a little bit above is to set a nut on top of it or screw it on if you can and weld or braze it to the nut making sure not to weld it to your part and remove with a wrench. Good luck!
 
You could try ferric chloride on the broken tap/ hole. The ferric will eat the tap or threads around it.

Rudy
 
I see where you are going with the acid idea. Have you ever tried this before? I don't have ferric, but I do use muriatic acid to etch my damascus with. I think it is a little stronger. If it works, I am sure that it will enlarge the hole, but I was planning on having to do that anyway.

Thanks!
 
If you want a really strong acid, there is a product called tap-out. I got some from a machinist friend a while back. It's basically nitric acid so if you come across some, be careful with it. I actually got some in my eye one time while I was playing around dissolving pennies. I got to an eye wash station in time and I'm lucky to still have my eyesight.
 
I have used Ferric Chloride on a few taps. The cheapest way is to eat it out with Ferric Chloride. Coat your blade in some kind of coating, Polyurethane will work, to keep the acid away from the blade. The tap is just too small to break out. Some machine shops can remove it with a EDM, it is such a small tap. I would tap it 2-56. I don't use anything smaller than 2-56.
 
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scherar said:
I see where you are going with the acid idea. Have you ever tried this before? I don't have ferric, but I do use muriatic acid to etch my damascus with. I think it is a little stronger. If it works, I am sure that it will enlarge the hole, but I was planning on having to do that anyway.

Thanks!
Click to expand...

Yes I have, a few times.
It seems that it disolved hardened steel (tap) faster than unhardened (?). I've never used muriatic, except on brickwork. Can't hurt to try a little. Post your results.

Rudy
 
Why not just move 1/16 up or down or left or right and just drill a new hole?

Assuming that your blade has not been heat treated yet you can heat up that area with a torch and anneal the tap. Then drill it out.
 
I am trying the muriatic acid today. The only hard thing is being able to break up or move the tap after the acid has worked on it for a while. It is such a small hole/piece, getting some sort of punch in it to try and knock it out is proving difficult.

I have thought about just moving my holes, but, I already drilled one of the bolsters with the two holes for the screws. They were only the tap size holes. I did this by temperarily gluing the one bolster to the tang where it was centered in place and then drilling through both the bolster and tang. I don't normally do it this way, but I just wanted to make sure the holes were as symetrical as possible since they would be seen with the screws. Typically it isn't as important when the pins are peined and don't show. Bolsters are still a grey area for me, so I don't know if my method is 100% efficient.

I also thought about putting two mosaic 1/8" pins in the mosaic damascis bolsters, but I am unsure about this method. Has anyone ever done this? I have seen a couple of knives in the Jantz catalog, but didn't know how great that method is. I am not sure exactly how they are attached. Epoxied, JB welded, etc.. I also need to be able to remove the bolsters after shaped with the handle to heat color them.

Thanks
 
Using epoxy or JB weld to hold on bolsters is a bad idea, I use these to seal under the bolster on carbon steel and damascus blades. Either peen pins or screws would be your best bet, think I would stay away from mosaic pins unless you used another mechanical attachment.
 
That is what I thought. I use JB weld on my bolsters for a sealant also. Just wasn't sure what the technique was for the people that use the mosaic pins.
 
If the hole is accessable from both sides....let your acid work a while then insert a drill bit upside down in your drill press and use it as a press to push out the (hopefully weakened) tap. It has worked for me on several booboos. l also have an arbor press that works really well with a whack on top.

Rudy
 
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