Broken Tap

[Jofus 0]

I decided to drill and tap my Mosin 91/30 for the ATI standard scope mount today. I've got the holes drilled just fine, but when I went to tap the front hole, the damn tap broke. I used cutting oil and backed it out every 1/4 turn, but it just seized and snapped. Now I have about 1/4 inch inside the area just behind the chamber itself.

 

I did a search on the forum, because I remember some poor fella had a similar problem when he was tapping the hole for his bullet guide. This is different because I can't drill a new hole, and have to get the tap out anyway in order for the bolt to shut. I tried whacking the hell out of it, trying to get it to shatter, but no dice. There isn't enought sticking out of the top to grab it with pliers and turn it, and I can't dent the tap materiel, so I'm not too sure an EZ out would help at all. Any ideas?

Thanks,

 

Jofus

[dinzag 31]

I know an EDM will do it, but could cost some $$$.

Try an easy-out. Use a grinding stone (fine point) in a dremel to put a divot in the center so you can get a good bite.

 

I snapped off a drill bit in my trunion bullet-guiding it, but I got some pliers on it.

Good Luck!

[Jofus 0]

Thanks, I'll give that a shot, running up to the hardware store now. Man this is freaking embarrassing!

[pesterbox 0]

Thanks, I'll give that a shot, running up to the hardware store now. Man this is freaking embarrassing!

 

 

Jofus, I don't know if you have access to a welder, but you can take a nut(new one without grease and crud) with the inside diameter smaller than the outside diameter of the tap. Place the nut on the tap and center it and then use a stainless steel welding rod to place a weld on the inside of the nut. Make sure that the nut is centered on the tap and that there is no part of the opening where the weld will touch the receiver. Let it cool and if possible spray with WD-40 as you work it back and forth to remove. You can't use just any welding rod as it will not weld to the tap. Hope this helps. Randall.

Edited January 13, 2006 by pesterbox

[G O B 3,516]

Go to the hardware store and get some 3" powder actuated type masonry nails (brush nails). These are hard and TOUGH! Carefully break the center out of the tap with one of these nails as a centerpunch- use a BIG hammer and hit HARD. The trick is that you want hammer speed to SHATTER the tap. (Hold the 'punch' in a vicegrip -it will save much cursing!)

 

Good luck.

 

 

G O B

[Jofus 0]

I like the nut idea, but I don't have access to a setup. I'll give the nail punch a try. I can't seem to even chip the thing, even with the best punch they had down at the hardware store. I've boogered the edges of the hole so far, but I figure I can dress them with a file, plus that'll be under the scope mount. If I can't get it out by Tuesday, a gunsmith a town over said he could give it a shot. Thanks for help guys, I appreciate it.

[Bvamp 604]

my machinist friends tell me of guys doing this once in a while in the shop, mainly due to not cleaning the tap flutes out, also because of tapping too fast... if you CAN get to the end of the tap, the first thing is needle nosed pliars ground down to fit into the flutes of the tap, although you cant have the flutes filled with stock cuttings. if thats the case, ask tony if he knows what the next best thing is. you ruin a good pair of needlenose, but it should work if you tap them in. also use lube or oil profusely when you do it. a little heat might help if you think you just need a little more to it. also, the deeper you can get the points of the needle nose in there, the better. just dont break them off in there if you can help it, so that you can get another pair to finish the job if it starts to work for you and you muck the tool up.

 

ive heard of doing what GOB says to do, but I have personally not seen it done.

 

one other thing I have heard of, and I only heard them talk about it once, as it was some 50,000$ injection mould that needed the tap removed, was to retap for a larger tap to get access to the smaller tap. dunno if that is even feasible in your case, and it is extreme. I know there is a special tap remover that you use at this point, as well. a hotrod shop or other custom milling place will be able to get it out for you, but there comes a price. hell two bolts that snapped off (not taps), in a driveshaft I had cost me 50 bucks ten years ago to have removed.

 

drilling the tap out is also doable, but expect to spin the drill SLOW as hell with lube, and to dull a couple to drill the sucker out. this is also extreme, as it could muck up the job completely. if you can get a hole in the tap, use another smaller tap to remove it.

 

this is all second hand information, but I can assure it is from a machine shop and from people that know what they are doing. hope you can find a solution to your problem.

[Unknown Poster 5]

You need an air compressor to clean the chips out first, then try a tap extractor, then try a small pointed prick punch to turn it back and forth to loosen it up then it will come out. The only other option is a tap burn out machine. On the larger taps the cement drills can be used to drill them out because the tips are carbide and they will cut right thru the tap. They will come out its no biggie it happens to all of us sooner or later.

[Bvamp 604]

unknown poster, is that a magic graphic I see there? bog wraith isnt it?

[ironhead7544 35]

Sears has a type of broken stud remover that might work. Supposed to be a lot better than an ez out.

[G O B 3,516]

I've never had more than limited luck with tap outs. Usually it is easiest to bust the center of the tap out. The more threads that are stuck in the workpiece, the harder it is to do. If you can find one of the "micro" torches, you can heat the tap to "orange" and let it air cool. That will remove the temper from the tap so that it can be centerpunched and drilled out with a good bit. On larger taps I have had success with welding a piece of drill rod to the spider (centre) and working it out with vicegrips.

Good luck, it's seldom easy.

 

GO B

[Jofus 0]

We got it out! My dad took it into his buddy's machine shop. Not positive what he did, because I was able to run a good tap thru again and the threads are fine. Thanks for all the helpful advice...that whole situation is just embarrassing. I'd advise anyone using the ATI scope mount kit to get their own 10/32 tap and not use the one in the kit. The drill bits were fine, just that tap was poop!

Edited January 18, 2006 by Jofus

[Unknown Poster 5]

The key thing to using a Tap Extractor(fingers) is to blow out the hole really good from the chips that are in there. You must get the chips out before you try the extractor or try to turn the tap. I never had them work until i seen an old timer working with me show me how to use them properly. I'm sorry to say its a lost art now with these great old guys who knew how to get things done are long gone now. I was a Class A machine assembler and we built cnc machines and chuckers. Then i built 155mm howitzers for the US Army. My last job was working for one of the top engineering groups in the country in the most modern failure analysis, product reliability and product development lab in the country. I have had some interesting jobs before I retired @55. My point is i did pass on some of my experiences to my sons otherwise it goes to the grave with me and thats not good.

[G O B 3,516]

UKP, I know what you mean about passing it on. Many of the younger guys act like learning anything is beneath them. I try to tell them that if you are going to do something for 30-40 years--you should make it your business to learn everything you can and get GOOD at it!

 

G O B